Search

In conjunction with the pressing global issue of climate change and the associated concern over global warming, increasing interest has emerged in the exploration of carbon dioxide (CO2) as a resource for the generation of a diverse array of products intended to serve societal needs. This study presents the development of an ATP-free and NAD-balanced in vitro synthetic enzymatic biosystem (ivSEB), which comprises only five cascade thermophilic enzymes, designed for the synthesis of L-malate through CO2 fixation powered by the utilization of D-glucose as a substrate. This designed ivSEB yields two moles of L-malate from one mole of D-glucose and two moles of CO2. Through meticulous refinement of reaction conditions and enzyme loading amounts, this ivSEB has demonstrated its capability to produce 6.85 mM of L-malate via CO2 fixation from an initial 5 mM of D-glucose with a molar product yield of 68.5%, and 2.45 mM of L-lactate as a byproduct. In the pursuit of assessing the industrial feasibility of this ivSEB, the study further subjected the system to the utilization of a high concentration (45.70 mM) of D-glucose. Although this endeavor necessitates additional optimization for enhanced efficiency, the present findings herald the emergence of an alternative avenue for the sustainable production of L-malate through CO2 fixation, thus bearing substantial promise for addressing ecological and industrial imperatives. [ABSTRACT FROM AUTHOR]

Acinetobacter baumannii is an opportunistic human pathogen which can use host-derived L-carnitine as sole carbon and energy source. Recently, an L-carnitine transporter (Aci1347) and a specific monooxygense (CntA/CntB) for the intracellular cleavage of L-carnitine have been characterized. Subsequent conversion of the resulting malic semialdehyde into the central metabolite L-malate was hypothesized. Alternatively, L-carnitine degradation via D-malate with subsequent oxidation into pyruvate was proposed. Here we describe the in vitro and in vivo reconstitution of the entire pathway, starting from the as yet uncharacterized gene products of the carnitine degradation gene operon. Using recombinantly purified enzymes, enantiomer-specific formation of D-malate by the NAD(P)+-dependent malic semialdehyde dehydrogenase (MSA-DH) is demonstrated. The solved X-ray crystal structure of tetrameric MSA-DH reveals the key catalytic residues Cys290 and Glu256, accessible through opposing substrate and cofactor funnels. Specific substrate binding is enabled by Arg166, Arg284 and Ser447 while dual cofactor specificity for NAD+ and NADP+ is mediated by Asn184. The subsequent conversion of the unusual D-malate reaction product by an uncharacterized NAD+-dependent malate dehydrogenase (MDH) is shown. Tetrameric MDH is a ß-decarboxylating dehydrogenase that synthesizes pyruvate. MDH experiments with alternative substrates showed a high degree of substrate specificity. Finally, the entire A. baumannni pathway was heterologously reconstituted, allowing E. coli to grow on L-carnitine as a carbon and energy source. Overall, the metabolic conversion of L-carnitine via malic semialdehyde and D-malate into pyruvate, CO2 and trimethylamine was demonstrated. Trimethylamine is also an important gut microbiota-dependent metabolite that is associated with an increased risk of cardiovascular disease. The pathway reconstitution experiments allowed us to assess the TMA forming capacity of gut microbes which is related to human cardiovascular health. [ABSTRACT FROM AUTHOR]

The plerocercoid larva of Spirometra mansoni can cause a parasitic zoonosis—sparganosis. Malate dehydrogenase (MDH) plays a very important role in the life activities of parasites. However, little is known about the MDH family in S. mansoni. We identified eight new MDH members in S. mansoni in this study. Clustering analysis divided SmMDHs into two groups and revealed patterns similar to the conserved motif organization. RT–qPCR suggested that five MDHs were highly expressed in the mature proglottid and that three MDHs were highly expressed in the gravid proglottid. Phylogenetic analysis revealed that SmMDHs contain both conserved family members and members in the process of further diversification. rSmMDH has an NAD binding domain, a dimer interface and a substrate binding domain. Natural SmMDH was immunolocalized in the tissues and follicles around the uterus in the mature or gravid proglottid and eggshells. The maximum forward and reverse reaction activities of rSmMDH were observed at pH 8.5 and 9.0, respectively. The optimum temperature for enzyme activity was 37 °C in the forward reaction and 40 °C in the reverse reaction. These results lay the foundation for studying the molecular functions and mechanisms of MDHs in S. mansoni and related taxa. [ABSTRACT FROM AUTHOR]

Pseudomonas fragi (P. fragi) is usually detected in low-temperature meat products, and seriously threatens food safety and human health. Therefore, the study investigated the antibacterial mechanism of linalool against P. fragi from membrane damage and metabolic disruption. Results from field-emission transmission electron microscopy (FETEM) and atomic force microscopy (AFM) showed that linalool damage membrane integrity increases surface shrinkage and roughness. According to Fourier transform infrared (FTIR) spectra results, the components in the membrane underwent significant changes, including nucleic acid leakage, carbohydrate production, protein denaturation and modification, and fatty acid content reduction. The data obtained from amino acid metabolomics indicated that linalool caused excessive synthesis and metabolism of specific amino acids, particularly tryptophan metabolism and arginine biosynthesis. The reduced activities of glucose 6-phosphate dehydrogenase (G6PDH), malate dehydrogenase (MDH), and phosphofructokinase (PFK) suggested that linalool impair the respiratory chain and energy metabolism. Meanwhile, genes encoding the above enzymes were differentially expressed, with pfkB overexpression and zwf and mqo downregulation. Furthermore, molecular docking revealed that linalool can interact with the amino acid residues of G6DPH, MDH and PFK through hydrogen bonds. Therefore, it is hypothesized that the mechanism of linalool against P. fragi may involve cell membrane damage (structure and morphology), disturbance of energy metabolism (TCA cycle, EMP and HMP pathway) and amino acid metabolism (cysteine, glutamic acid and citrulline). These findings contribute to the development of linalool as a promising antibacterial agent in response to the food security challenge. [ABSTRACT FROM AUTHOR]

A 60 days study was conducted to evaluate the physiological response of indigenous species Labeo rohita (LR) and indigenous predator Chitala chitala (CC) in presence of an invasive species Piaractus brachypomus (PB). Two treatment groups as LR + PB (T1) and LR + PB + CC (T2) with individual control groups as T0LR, T0PB and T0CC were designed in triplicates. Fingerlings of LR, PB and CC were randomly distributed into 15 circular tanks with a stocking ratio of 1:1 and 1:1:0.3 in T1 and T2 group, respectively and 10 nos. each of LR, PB and CC in respective control groups. At first 15 min of the experiment, cortisol level was found significantly (P < 0.05) higher in all three experimental fishes in T1 and T2 groups. With the experimental duration, the level of stress hormone (cortisol), oxidative stress enzymes (superoxide dismutase, catalase, and glutathione peroxidase), tissue metabolic enzymes (lactate dehydrogenase and malate dehydrogenase), serum metabolic enzymes (transaminase enzymes) and blood glucose level were significantly (P < 0.05) increased in T1 and T2 groups for LR and CC whereas, no variation (P > 0.05) were observed for PB in both T1 and T2 groups. The total antioxidant capacity (TAC), liver glycogen, total protein, albumin and globulin were found to be significantly (P < 0.05) decreased in LR in the presence of PB and CC. The present study provides a preliminary insight into the biological interaction between native and invasive species and their physiological responses in the presence of native predator with higher trophic index. Thus, the results of the study suggest the superior traits of invasive P. brachypomus try to dominate the other two native species by negatively influencing the native fauna even with a higher trophic index (C. chitala). [ABSTRACT FROM AUTHOR]

Metabolic rewiring during the proliferation-to-quiescence transition is poorly understood. Here, using a model of contact inhibition-induced quiescence, we conducted 13C-metabolic flux analysis in proliferating (P) and quiescent (Q) mouse embryonic fibroblasts (MEFs) to investigate this process. Q cells exhibit reduced glycolysis but increased TCA cycle flux and mitochondrial respiration. Reduced glycolytic flux in Q cells correlates with reduced glycolytic enzyme expression mediated by yes-associated protein (YAP) inhibition. The increased TCA cycle activity and respiration in Q cells is mediated by induced mitochondrial pyruvate carrier (MPC) expression, rendering them vulnerable to MPC inhibition. The malate-to-pyruvate flux, which generates NADPH, is markedly reduced by modulating malic enzyme 1 (ME1) dimerization in Q cells. Conversely, the malate dehydrogenase 1 (MDH1)-mediated oxaloacetate-to-malate flux is reversed and elevated in Q cells, driven by high mitochondrial-derived malate levels, reduced cytosolic oxaloacetate, elevated MDH1 levels, and a high cytoplasmic NAD+/NADH ratio. Transcriptomic analysis revealed large number of genes are induced in Q cells, many of which are associated with the extracellular matrix (ECM), while YAP-dependent and cell cycle-related genes are repressed. The results suggest that high TCA cycle flux and respiration in Q cells are required to generate ATP and amino acids to maintain de-novo ECM protein synthesis and secretion. Metabolic changes happening when cells enter quiescence are poorly understood. Here, the authors report that quiescent cells exhibit reduced glycolysis mediated by YAP inhibition and increased mitochondrial activity mediated by pyruvate carrier induced expression. [ABSTRACT FROM AUTHOR]

The effect of hypoxia on the level of expression of pyruvate kinase (PKM), octopine dehydrogenase (OcDH), and malate dehydrogenase (MDH) genes in the gill tissue of the Mediterranean mussel Mytilus galloprovincialis (L., 1819) was studied experimentally. The control group of mollusks was kept at 9–10°C, and the oxygen level in the water was 8.5 mg O2 L–1. The experimental levels were at 9–10°C and 2.2 mg O2 L–1. The exposure was 24 and 72 h. Some of the individuals were subsequently subjected to the reoxygenation procedure. Under conditions of hypoxia, the expression level of OcDH and MDH genes increased by three and two times, respectively (p < 0.05). At the same time, OcDH expression showed sensitivity to the oxygen content in the medium. Under the conditions of reoxygenation, the process was completely suppressed. The expression of the PKM gene, on the contrary, did not depend on hypoxic effects and remained at the level of the control values. [ABSTRACT FROM AUTHOR]

During photosynthesis, reactive oxygen species (ROS) are formed, including hydrogen peroxide (H2O2) and singlet oxygen (1O2), which have putative roles in signalling, but their involvement in photosynthetic acclimation is unclear. Due to extreme reactivity and a short lifetime, 1O2 signalling occurs via its reaction products, such as oxidised poly-unsaturated fatty acids in thylakoid membranes. The resulting lipid peroxides decay to various aldehydes and reactive electrophile species (RES). Here, we investigated the role of ROS in the signal transduction of high light (HL), focusing on GreenCut2 genes unique to photosynthetic organisms. Using RNA seq. data, the transcriptional responses of Chlamydomonas reinhardtii to 2 h HL were compared with responses under low light to exogenous RES (acrolein; 4-hydroxynonenal), β-cyclocitral, a β-carotene oxidation product, as well as Rose Bengal, a 1O2-producing photosensitiser, and H2O2. HL induced significant (p < 0.05) up- and down-regulation of 108 and 23 GreenCut2 genes, respectively. Of all HL up-regulated genes, over half were also up-regulated by RES, including RBCS1 (ribulose bisphosphate carboxylase small subunit), NPQ-related PSBS1 and LHCSR1. Furthermore, 96% of the genes down-regulated by HL were also down-regulated by 1O2 or RES, including CAO1 (chlorophyllide-a oxygnease), MDH2 (NADP-malate dehydrogenase) and PGM4 (phosphoglycerate mutase) for glycolysis. In comparison, only 0–4% of HL-affected GreenCut2 genes were similarly affected by H2O2 or β-cyclocitral. Overall, 1O2 plays a significant role in signalling during the initial acclimation of C. reinhardtii to HL by up-regulating photo-protection and carbon assimilation and down-regulating specific primary metabolic pathways. Our data support that this pathway involves RES. [ABSTRACT FROM AUTHOR]

The aims of this study were to examine the effects of pyridoxine administration on the activities of cardiac antioxidant stress enzymes superoxide dismutase (SOD) and catalase (CAT) and enzyme indicators of cardiometabolic status, lactate and malate dehydrogenase (LDH, MDH), as well as LDH and MDH isoforms' distribution in the cardiac tissue of healthy and diabetic Wistar male rats. Experimental animals were divided into five groups: C1—control (0.9% sodium chloride—NaCl—1 mL/kg, intraperitoneally (i.p.), 1 day); C2—second control (0.9% NaCl 1 mL/kg, i.p., 28 days); DM—diabetes mellitus (streptozotocin 100 mg/kg in 0.9% NaCl, i.p., 1 day); P—pyridoxine (7 mg/kg, i.p., 28 days); and DM + P—diabetes mellitus and pyridoxine (streptozotocin 100 mg/kg, i.p., 1 day and pyridoxine 7 mg/kg, i.p., 28 days). Pyridoxine treatment reduced CAT and MDH activity in diabetic rats. In diabetic rats, the administration of pyridoxine increased LDH1 and decreased LDH4 isoform activities, as well as decreased peroxisomal MDH and increased mitochondrial MDH activities. Our findings highlight the positive effects of pyridoxine administration on the complex interplay between oxidative stress, antioxidant enzymes, and metabolic changes in diabetic cardiomyopathy. [ABSTRACT FROM AUTHOR]

There is an increasing requirement for the discovery of new anthelmintics with resistance to existing drugs on the rise. Current strategies focus on targeting carbohydrate metabolism, with glycolytic enzymes and transporters proving to be attractive druggable targets; however, these often show a lack of efficacy during in vivo infections and have a lack of specificity. Recent studies have unearthed the ability of helminths to manipulate short-chain fatty acid (SCFA) and bioactive lipid production, as possible alternative immunomodulatory strategies for establishing chronic infection. There is an urgent need to establish if these metabolic pathways are critical for parasite survival, as these could present as an exciting new avenue for anthelmintic discovery. Helminths can adapt to environmental conditions in the host, utilising anaerobic processes like fermentation and malate dismutation to produce energy from carbohydrate. Although targeting carbohydrate metabolism is an established therapeutic strategy to combat helminth infection, questions remain over the metabolic pathways they employ as adults to survive and evade host immunity. Helminths also use amino acid, polyunsaturated fatty acid (PUFA), and cholesterol metabolism, a possible strategy favouring the production of immunomodulatory compounds that may influence survival in the host. Here, we discuss the significance of these differing metabolic pathways and whether targeting of helminth metabolic pathways may allow for the development of novel anthelmintics. [ABSTRACT FROM AUTHOR]

Organic acids play critical roles in fruit physiological metabolism and sensory quality. However, the conventional storage of apple fruit at 0 ± 0.1 °C cannot maintain fruit acidity efficiently. This study investigated near-freezing temperature (NFT) storage for 'Golden Delicious' apples, and the quality parameters, organic acid content, and malate metabolism were studied. The results indicate that NFT storage at −1.7 ± 0.1 °C effectively maintained the postharvest quality of apple fruit when compared to traditional storage at 0 ± 0.1 °C. Fruit that underwent NFT storage showed a better appearance and lower respiratory rate, ethylene production, weight loss, and malondialdehyde (MDA) content but higher firmness and soluble solids content. Further, fruit after NFT storage contained higher titratable acid (18.75%), malate (51.61%), citrate (36.59%), and succinate (2.12%) content when compared to the control after 250 days. This was achieved by maintaining higher cytosolic NAD-dependent malate dehydrogenase (cyNAD-MDH), phosphoenolpyruvate carboxylase (PEPC), vacuolar H+-ATPase (V-ATPase), and vacuolar inorganic pyrophosphatase (V-PPase) activities that promote malate biosynthesis and accumulation while inhibiting enzyme activity that is responsible for malate decomposition, including phosphoenolpyruvate carboxylase kinase (PEPCK) as well as the cytosolic NAD phosphate-dependent malic enzyme (cyNADP-ME). Further, storage at NFTs maintained a higher expression of malate biosynthesis-related genes (MdcyNAD-MDH and MdPEPC) and transport-related genes (MdVHA and MdVHP) while suppressing malate consumption-related genes (MdcyME and MdPEPCK). The results demonstrate that NFT storage could be an effective application for apple fruit, which maintains postharvest quality and alleviates organic acid degradation. [ABSTRACT FROM AUTHOR]

Enzymes of the central metabolism tend to assemble into transient supramolecular complexes. However, the functional significance of the interactions, particularly between enzymes catalyzing non-consecutive reactions, remains unclear. Here, by co-localizing two non-consecutive enzymes of the TCA cycle from Bacillus subtilis, malate dehydrogenase (MDH) and isocitrate dehydrogenase (ICD), in phase separated droplets we show that MDH-ICD interaction leads to enzyme agglomeration with a concomitant enhancement of ICD catalytic rate and an apparent sequestration of its reaction product, 2-oxoglutarate. Theory demonstrates that MDH-mediated clustering of ICD molecules explains the observed phenomena. In vivo analyses reveal that MDH overexpression leads to accumulation of 2-oxoglutarate and reduction of fluxes flowing through both the catabolic and anabolic branches of the carbon-nitrogen intersection occupied by 2-oxoglutarate, resulting in impeded ammonium assimilation and reduced biomass production. Our findings suggest that the MDH-ICD interaction is an important coordinator of carbon-nitrogen metabolism. Enzymes of central metabolism tend to assemble into transient supramolecular complexes. Here, the authors stoichiometrically perturbed the supramolecular complex of TCA cycle enzymes in B. subtilis and propose that MDH-ICD clustering causes 2-oxoglutartae sequestration by reducing its diffusion rate, a mechanism that has evolved to regulate flux through the carbon-nitrogen metabolic branch-point. [ABSTRACT FROM AUTHOR]

Summary: Although saline–alkali stress can improve tomato quality, the detailed molecular processes that balance stress tolerance and quality are not well‐understood.Our research links nitric oxide (NO) and γ‐aminobutyric acid (GABA) with the control of root malate exudation and fruit malate storage, mediated by aluminium‐activated malate transporter 9/14 (SlALMT9/14). By modifying a specific S‐nitrosylated site on pyruvate‐dependent GABA transaminase 1 (SlGABA‐TP1), we have found a way to enhance both plant's saline–alkali tolerance and fruit quality.Under saline–alkali stress, NO levels vary in tomato roots and fruits. High NO in roots leads to S‐nitrosylation of SlGABA‐TP1/2/3 at Cys316/258/316, reducing their activity and increasing GABA. This GABA then reduces malate exudation from roots and affects saline–alkali tolerance by interacting with SlALMT14. In fruits, a moderate NO level boosts SlGABA‐TP1 expression and GABA breakdown, easing GABA's block on SlALMT9 and increasing malate storage. Mutants of SlGABA‐TP1C316S that do not undergo S‐nitrosylation maintain high activity, supporting malate movement in both roots and fruits under stress.This study suggests targeting SlGABA‐TP1Cys316 in tomato breeding could significantly improve plant's saline–alkali tolerance and fruit quality, offering a promising strategy for agricultural development. [ABSTRACT FROM AUTHOR]

Malate dehydrogenases (MDHs) catalyze a reversible NAD(P)‐dependent‐oxidoreductase reaction that plays an important role in central metabolism and redox homeostasis of plant cells. Recent studies suggest a moonlighting function of plastidial NAD‐dependent MDH (plNAD‐MDH; EC 1.1.1.37) in plastid biogenesis, independent of its enzyme activity. In this study, redox effects on activity and conformation of recombinant plNAD‐MDH from Arabidopsis thaliana were investigated. We show that reduced plNAD‐MDH is active while it is inhibited upon oxidation. Interestingly, the presence of its cofactors NAD+ and NADH could prevent oxidative inhibition of plNAD‐MDH. In addition, a conformational change upon oxidation could be observed via non‐reducing SDS‐PAGE. Both effects, its inhibition and conformational change, were reversible by re‐reduction. Further investigation of single cysteine substitutions and mass spectrometry revealed that oxidation of plNAD‐MDH leads to oxidation of all four cysteine residues. However, cysteine oxidation of C129 leads to inhibition of plNAD‐MDH activity and oxidation of C147 induces its conformational change. In contrast, oxidation of C190 and C333 does not affect plNAD‐MDH activity or structure. Our results demonstrate that plNAD‐MDH activity can be reversibly inhibited, but not inactivated, by cysteine oxidation and might be co‐regulated by the availability of its cofactors in vivo. [ABSTRACT FROM AUTHOR]

Background: A series of studies have demonstrated the emerging involvement of transfer RNA (tRNA) processing during the progression of tumours. Nevertheless, the roles and regulating mechanisms of tRNA processing genes in neuroblastoma (NB), the prevalent malignant tumour outside the brain in children, are yet unknown. Methods: Analysis of multi‐omics results was conducted to identify crucial regulators of downstream tRNA processing genes. Co‐immunoprecipitation and mass spectrometry methods were utilised to measure interaction between proteins. The impact of transcriptional regulators on expression of downstream genes was measured by dual‐luciferase reporter, chromatin immunoprecipitation, western blotting and real‐time quantitative reverse transcription‐polymerase chain reaction (RT‐PCR) methods. Studies have been conducted to reveal impact and mechanisms of transcriptional regulators on biological processes of NB. Survival differences were analysed using the log‐rank test. Results: c‐Myc was identified as a transcription factor driving tRNA processing gene expression and subsequent malate‐aspartate shuttle (MAS) in NB cells. Mechanistically, c‐Myc directly promoted the expression of glutamyl‐prolyl‐tRNA synthetase (EPRS) and leucyl‐tRNA synthetase (LARS), resulting in translational up‐regulation of glutamic‐oxaloacetic transaminase 1 (GOT1) as well as malate dehydrogenase 1 (MDH1) via inhibiting general control nonrepressed 2 or activating mechanistic target of rapamycin signalling. Meanwhile, lamin A (LMNA) inhibited c‐Myc transactivation via physical interaction, leading to suppression of MAS, aerobic glycolysis, tumourigenesis and aggressiveness. Pre‐clinically, lobeline was discovered as a LMNA‐binding compound to facilitate its interaction with c‐Myc, which inhibited aminoacyl‐tRNA synthetase expression, MAS and tumour progression of NB, as well as growth of organoid derived from c‐Myc knock‐in mice. Low levels of LMNA or elevated expression of c‐Myc, EPRS, LARS, GOT1 or MDH1 were linked to a worse outcome and a shorter survival time of clinical NB patients. Conclusions: These results suggest that targeting c‐Myc transactivation by LMNA inhibits tRNA processing essential for MAS and tumour progression. [ABSTRACT FROM AUTHOR]

Sitravatinib (MGCD516) is an orally available, small molecule, tyrosine kinase inhibitor that has been evaluated in patients with advanced solid tumors. Concentration‐corrected QT interval (QTc; C‐QTc) modeling was undertaken, using 767 matched concentration‐ECG observations from 187 patients across two clinical studies in patients with advanced solid malignancies, across a dose range of 10–200 mg, via a linear mixed‐effects (LME) model. The effect on heart rate (HR)‐corrected QT interval via Fridericia's correction method (QTcF) at the steady‐state maximum concentration (Cmax,ss) for the sitravatinib proposed therapeutic dosing regimen (100 mg malate once daily [q.d.]) without and with relevant intrinsic and extrinsic factors were predicted. No significant changes in HR from baseline were observed. Hysteresis between sitravatinib plasma concentration and change in QTcF from baseline (ΔQTcF) was not observed. There was no significant relationship between sitravatinib plasma concentration and ΔQTcF. The final C‐QTc model predicted a mean (90% confidence interval [CI]) ΔQTcF of 3.92 (1.95–5.89) ms and 2.94 (0.23–6.10) ms at the proposed therapeutic dosing regimen in patients with normal organ function (best case scenario) and patients with hepatic impairment (worst‐case scenario), respectively. The upper bounds of the 90% CIs were below the regulatory threshold of concern of 10 ms. The results of the described C‐QTc analysis, along with corroborating results from nonclinical safety pharmacology studies, indicate that sitravatinib has a low risk of QTc interval prolongation at the proposed therapeutic dose of 100 mg malate q.d. [ABSTRACT FROM AUTHOR]

Fusarium solani is a pathogenic fungus that causes significant harm, leading to crop yield reduction, fruit quality reduction, postharvest decay, and other diseases. This study used potato glycoside alkaloids (PGA) as inhibitors to investigate their effects on the mitochondrial structure and tricarboxylic acid (TCA) cycle pathway of F. solani. The results showed that PGA could inhibit the colony growth of F. solani (54.49%), resulting in the disappearance of the mitochondrial membrane and the loss of contents. PGA significantly decreased the activities of aconitase (ACO), isocitrate dehydrogenase (IDH), α-ketoglutarate dehydrogenase (α-KGDH), succinate dehydrogenase (SDH), fumarase (FH), malate dehydrogenase (MDH), succinyl-CoA synthetase (SCS), and increased the activity of citrate synthase (CS) in F. solani. After PGA treatment, the contents of acetyl coenzyme A (CoA), citric acid (CA), malic acid (L-MA), and α-ketoglutaric acid (α-KG) in F. solani were significantly decreased. The contents of isocitric acid (ICA), succinyl coenzyme A (S-CoA), succinic acid (SA), fumaric acid (FA), and oxaloacetic acid (OA) were significantly increased. Transcriptomic analysis showed that PGA could significantly affect the expression levels of 19 genes related to TCA cycle in F. solani. RT-qPCR results showed that the expression levels of ACO, IDH, α-KGDH, and MDH-related genes were significantly down-regulated, and the expression levels of SDH and FH-related genes were significantly upregulated, which was consistent with the results of transcriptomics. In summary, PGA can achieve antifungal effects by reducing the tricarboxylic acid cycle's flow and regulating key genes' expression levels. This study reveals the antifungal mechanism of PGA from the perspective of TCA cycle, and provides a theoretical basis for the development and application of PGA as a biopesticide. [ABSTRACT FROM AUTHOR]

Adaptation to chronic hypoxia occurs through changes in protein expression, which are controlled by hypoxia-inducible factor 1α (HIF1α) and are necessary for cancer cell survival. However, the mechanisms that enable cancer cells to adapt in early hypoxia, before the HIF1α-mediated transcription programme is fully established, remain poorly understood. Here we show in human breast cancer cells, that within 3 h of hypoxia exposure, glycolytic flux increases in a HIF1α-independent manner but is limited by NAD+ availability. Glycolytic ATP maintenance and cell survival in early hypoxia rely on reserve lactate dehydrogenase A capacity as well as the activity of glutamate-oxoglutarate transaminase 1 (GOT1), an enzyme that fuels malate dehydrogenase 1 (MDH1)-derived NAD+. In addition, GOT1 maintains low α-ketoglutarate levels, thereby limiting prolyl hydroxylase activity to promote HIF1α stabilisation in early hypoxia and enable robust HIF1α target gene expression in later hypoxia. Our findings reveal that, in normoxia, multiple enzyme systems maintain cells in a primed state ready to support increased glycolysis and HIF1α stabilisation upon oxygen limitation, until other adaptive processes that require more time are fully established. Synopsis: Long term survival of cancer cells in hypoxia is dependent upon HIF1α activity for energy production. However, it is unclear how cells survive before HIF1α-transcribed genes are robustly expressed. This study investigated the early mechanism of human cancer cell survival upon hypoxia exposure. Shortly upon exposure to hypoxia, human breast cancer cells have increased glycolysis independent of HIF1α and without detectable changes in glycolytic enzyme expression. This glycolytic boost relies on NAD+ that is provided by reserve lactate dehydrogenase A (LDHA) capacity and malate dehydrogenase 1 (MDH1) activity fuelled by glutamate-oxoglutarate transaminase 1 (GOT1). However, NAD+ is still limiting for maximal flux through ATP-producing lower glycolysis, as indicated by efflux of glucose carbons to α-glycerophosphate (α-GP). Although MDH1 flux does not increase, combined inhibition of GOT1 and LDHA results in attenuated ATP production and cell survival. Consumption of α-ketoglutarate by GOT1 also limits prolyl hydroxylase activity and enables HIF1α stabilisation for long term hypoxic responses. In early hypoxia, NAD+ required for glycolytic ATP production is provided by lactate dehydrogenase A and GOT1-fuelled malate dehydrogenase 1 activities before HIF1α-mediated cell survival mechanisms are established. [ABSTRACT FROM AUTHOR]

We compared the effects of chronic exogenous lactate and exercise training, which influence energy substrate utilization and body composition improvements at rest and during exercise, and investigated the availability of lactate as a metabolic regulator. The mice were divided into four groups: CON (sedentary + saline), LAC (sedentary + lactate), EXE (exercise + saline), and EXLA (exercise + lactate). The total experimental period was set at 4 weeks, the training intensity was set at 60–70% VO2max, and each exercise group was administered a solution immediately after exercise. Changes in the energy substrate utilization at rest and during exercise, the protein levels related to energy substrate utilization in skeletal muscles, and the body composition were measured. Lactate intake and exercise increased carbohydrate oxidation as a substrate during exercise, leading to an increased energy expenditure and increased protein levels of citrate synthase and malate dehydrogenase 2, key factors in the TCA(tricarboxylic acid) cycle of skeletal muscle. Exercise, but not lactate intake, induced the upregulation of the skeletal muscle glucose transport factor 4 and a reduction in body fat. Hence, chronic lactate administration, as a metabolic regulator, influenced energy substrate utilization by the skeletal muscle and increased energy expenditure during exercise through the activation of carbohydrate metabolism-related factors. Therefore, exogenous lactate holds potential as a metabolic regulator. [ABSTRACT FROM AUTHOR]

Objective: Reduction of cerebral ischemia-reperfusion injury (IRI)/re-oxygenation injury, is defined as the paradoxicalexacerbation of the cellular dysfunction and death, following restoration of the blood flow to previously ischemic tissues.The re-establishment of blood flow is essential to salvage the ischemic tissues. As a result, the treatment of IRI withnovel therapies, which have fewer side effects, are of great importance. Therefore, this study aimed to investigate theeffects of curcumin nanoparticle (CN) pre-treatment on the cerebral I/R rat model.Materials and Methods: In this experimental study, CN was administered to rats orally five days before the bilateralcommon carotid artery occlusion (BCCAO) and continued for three days. The intensity of oxidative stress, the activities ofantioxidant enzymes, glutathione (GSH) content, the activity of mitochondrial enzymes, including succinate dehydrogenase(SDH), malate dehydrogenase (MDH) and lactate dehydrogenase (LDH), curcumin bioavailability, pERK/ERK expressionratio and TFEB protein were studied. Data analysis was performed using Graphpad Prism V.8 software, one-way analysisof variance (ANOVA) with the statistical package for the social sciences (SPSS V.26 software).Results: Cerebral IRI-damage significantly increased the oxidative stress (P=0.0008) and decreased the activityof the antioxidant enzymes including catalase (CAT) (P

Simple Summary: When rainbow trout are exposed to elevated temperatures over the long term, adaptations occur. Understanding these adaptation processes can aid in evaluating the response of this fish species and related species to climate change, as well as in determining the maximum temperature they can tolerate before compromising their welfare. The present study aimed to investigate whether adaptations could also be observed in the gills. Gill structure and enzyme activities were examined in fish exposed to 20 °C for 32 days, in comparison to fish maintained at their temperature optimum of 9 °C. The study revealed significant changes in gill structure and metabolism, indicative of an adaptive response to elevated temperatures. Seven-month-old rainbow trout acclimated to 9 °C were used. The fish were gradually adapted to a water temperature of 20 °C over a period of seven days and then exposed to this temperature for 32 days. Changes in gill morphometry and histology and in enzyme activities in comparison to fish kept at 9 °C were investigated. No histopathological abnormalities were discerned at the heightened temperature. The gill epithelium thickened by approximately 40%, suggesting an increase in the branchial diffusion barrier for ions, water, and gases. Concurrently, there was a significant decrease in the activities of gill H+-ATPase and Na+/K+-ATPase, indicative of a reduction in osmoregulation under elevated temperatures. Carbonic anhydrase activity exhibited an increase following the 32-day exposure to 20 °C, potentially mitigating the adverse effects of increased gill epithelium thickness on gaseous exchange. There were no indications of gill surface enlargement as the measurements of the length of the primary and secondary lamellae, as well as of the distances between them, were similar at 9 and 20 °C. The activities of the gill enzymes associated with glycolysis and the citric acid cycle displayed a varied response following the 32-day exposure of rainbow trout to 20 °C. Pyruvate kinase decreased, while lactate dehydrogenase increased, and malate dehydrogenase remained constant. This might suggest a decrease in the glycolytic rate, a greater reliance on anaerobic pathways at 20 °C compared to 9 °C, and the consistent efficiency of the citric acid cycle in the gills of rainbow trout in response to elevated temperatures. In summation, the data suggest a remodeling of rainbow trout gills in response to elevated temperatures, affecting both morphometric and metabolic aspects. [ABSTRACT FROM AUTHOR]

Physaria fendleri is a member of the Brassicaceae that produces in its embryos hydroxy fatty acids, constituents of oils that are very valuable and widely used by industry for cosmetics, lubricants, biofuels, etc. Free of toxins and rich in hydroxy fatty acids, Physaria provides a promising alternative to imported castor oil and is on the verge of being commercialized. This study aims to identify important biochemical step(s) for oil synthesis in Physaria , which may serve as target(s) for future crop improvement. To advance towards this goal, the endosperm composition was analysed by LC-MS/MS to develop and validate culture conditions that mimic the development of the embryos in planta. Using developing Physaria embryos in culture and 13C-labeling, our studies revealed that: (i) Physaria embryos metabolize carbon into biomass with an efficiency significantly lower than other photosynthetic embryos; (ii) the plastidic malic enzyme provides 42% of the pyruvate used for de novo fatty acid synthesis, which is the highest measured so far in developing 'green' oilseed embryos; and (iii) Physaria uses non-conventional pathways to channel carbon into oil, namely the Rubisco shunt, which fixes CO2 released in the plastid, and the reversibility of isocitrate dehydrogenase, which provides additional carbon for fatty acid elongation. [ABSTRACT FROM AUTHOR]

The adaptation of plants to combined stresses requires unique responses capable of overcoming both the negative effects of each individual stress and their combination. Here, we studied the C3-C4 (C2) halophyte Sedobassia sedoides in response to elevated temperature (35 °C) and salinity (300 mM NaCl) as well as their combined effect. The responses we studied included changes in water–salt balance, light and dark photosynthetic reactions, the expression of photosynthetic genes, the activity of malate dehydrogenase complex enzymes, and the antioxidant system. Salt treatment led to altered water–salt balance, improved water use efficiency, and an increase in the abundance of key enzymes involved in intermediate C3-C4 photosynthesis (i.e., Rubisco and glycine decarboxylase). We also observed a possible increase in the activity of the C2 carbon-concentrating mechanism (CCM), which allowed plants to maintain high photosynthesis intensity and biomass accumulation. Elevated temperatures caused an imbalance in the dark and light reactions of photosynthesis, leading to stromal overreduction and the excessive generation of reactive oxygen species (ROS). In response, S. sedoides significantly activated a metabolic pathway for removing excess NADPH, the malate valve, which is catalyzed by NADP-MDH, without observable activation of the antioxidant system. The combined action of these two factors caused the activation of antioxidant defenses (i.e., increased activity of SOD and POX and upregulation of FDI), which led to a decrease in oxidative stress and helped restore the photosynthetic energy balance. Overall, improved PSII functioning and increased activity of PSI cyclic electron transport (CET) and C2 CCM led to an increase in the photosynthesis intensity of S. sedoides under the combined effect of salinity and elevated temperature relative to high temperature alone. [ABSTRACT FROM AUTHOR]

Glioma are clinically challenging tumors due to their location and invasiveness nature, which often hinder complete surgical resection. The evaluation of the isocitrate dehydrogenase mutation status has become crucial for effective patient stratification. Through a transdisciplinary approach, we have developed an 18F-labeled ligand for non-invasive assessment of the IDH1R132H variant by using positron emission tomography (PET) imaging. In this study, we have successfully prepared diastereomerically pure [18F]AG-120 by copper-mediated radiofluorination of the stannyl precursor 6 on a TRACERlab FX2 N radiosynthesis module. In vitro internalization studies demonstrated significantly higher uptake of [18F]AG-120 in U251 human high-grade glioma cells with stable overexpression of mutant IDH1 (IDH1R132H) compared to their wild-type IDH1 counterpart (0.4 vs. 0.013% applied dose/µg protein at 120 min). In vivo studies conducted in mice, exhibited the excellent metabolic stability of [18F]AG-120, with parent fractions of 85% and 91% in plasma and brain at 30 min p.i., respectively. Dynamic PET studies with [18F]AG-120 in naïve mice and orthotopic glioma rat model reveal limited blood-brain barrier permeation along with a low uptake in the brain tumor. Interestingly, there was no significant difference in uptake between mutant IDH1R132H and wild-type IDH1 tumors (tumor-to-blood ratio[40−60 min]: ~1.7 vs. ~1.3). In conclusion, our preclinical evaluation demonstrated a target-specific internalization of [18F]AG-120 in vitro, a high metabolic stability in vivo in mice, and a slightly higher accumulation of activity in IDH1R132H-glioma compared to IDH1-glioma. Overall, our findings contribute to advancing the field of molecular imaging and encourage the evaluation of [18F]AG-120 to improve diagnosis and management of glioma and other IDH1R132H-related tumors. [ABSTRACT FROM AUTHOR]

Isocitrate dehydrogenase is an enzyme converting isocitrate to α-ketoglutarate in the canonical tricarboxylic acid (TCA) cycle. There are three different types of isocitrate dehydrogenase documented in eukaryotes. Our study points out the complex evolutionary history of isocitrate dehydrogenases across kinetoplastids, where the common ancestor of Trypanosomatidae and Bodonidae was equipped with two isoforms of the isocitrate dehydrogenase enzyme: the NADP+-dependent isocitrate dehydrogenase 1 with possibly dual localization in the cytosol and mitochondrion and NADP+-dependent mitochondrial isocitrate dehydrogenase 2. In the extant trypanosomatids, isocitrate dehydrogenase 1 is present only in a few species suggesting that it was lost upon separation of Trypanosoma spp. and replaced by the mainly NADP+-dependent cytosolic isocitrate dehydrogenase 3 of bacterial origin in all the derived lineages. In this study, we experimentally demonstrate that the omnipresent isocitrate dehydrogenase 2 has a dual localization in both mitochondrion and cytosol in at least four species that possess only this isoform. The apparent lack of the NAD+-dependent isocitrate dehydrogenase activity in trypanosomatid mitochondrion provides further support to the existence of the noncanonical TCA cycle across trypanosomatids and the bidirectional activity of isocitrate dehydrogenase 3 when operating with NADP+ cofactor instead of NAD+. This observation can be extended to all 17 species analyzed in this study, except for Leishmania mexicana , which showed only low isocitrate dehydrogenase activity in the cytosol. The variability in isocitrate oxidation capacity among species may reflect the distinct metabolic strategies and needs for reduced cofactors in particular environments. [ABSTRACT FROM AUTHOR]

This project aims to solve the structure of the crenarchaeal Sulfolobus acidocaldarius enzyme malate synthase. Other known malate synthase enzymes have been found to require a magnesium ion in the active site to carry out catalytic activities, but a study reported that S. acidocaldarius malate synthase does not require magnesium. This suggests a novel mechanism for this enzyme. Additionally, the mature S. acidocaldarius protein is approximately 100 residues larger than any other structurally characterized malate synthase. It has also been reported to form a dimer, while previously solved structures have only displayed monomeric, trimeric, and hexameric arrangements. We plan to determine the structure experimentally. However, major advances in the accuracy of protein structure prediction were made recently by AlphaFold, an artificial intelligence system developed by DeepMind, which has revolutionized the field and has largely solved the protein folding problem. A similar AI system, RoseTTAFold, developed by David Baker's lab at the University of Washington, has been made publicly available. Here, we report our analysis of the structure of this protein, predicted using both of these algorithms and of a predicted structural model for the dimeric form of the enzyme using ClusPro. Our results strongly support a conserved catalytic mechanism requiring magnesium, which is common with all previously solved malate synthase isoforms. [ABSTRACT FROM AUTHOR]

Simple Summary: Long-term exposure to cadmium can cause liver toxicity, kidney toxicity, bone toxicity, and cancer in aquatic animals, which seriously endangers the health of aquatic animals and the quality of aquatic products. Chitosan can be combined with cadmium in aquaculture water through adsorption, thus alleviating the toxic effects of cadmium on aquatic animals. In this study, juvenile tilapia was fed with a formulated feed containing five different levels (0%, 0.5%, 1.0%, 1.5%, and 2.0%) of chitosan for 60 days, while the water in all experimental groups contained a Cd2+ concentration of 0.2 mg/L. The results indicated that dietary chitosan supplementation could alleviate the effects of Cd2+ stress on the muscle composition, digestive enzymes, lipid metabolism, and stress resistance, and their related gene expression, of juvenile tilapia. The aim of this study was to investigate the effects of dietary chitosan supplementation on the muscle composition, digestion, lipid metabolism, and stress resistance, and their related gene expression, of juvenile tilapia (Oreochromis niloticus) subjected to cadmium (Cd2+) stress. Juvenile tilapia with an initial body weight of 21.21 ± 0.24 g were fed with a formulated feed containing five different levels (0%, 0.5%, 1.0%, 1.5%, and 2.0%) of chitosan for 60 days, while the water in all experimental groups contained a Cd2+ concentration of 0.2 mg/L. The results showed that, compared with the control group (0% chitosan), the contents of crude fat and crude protein in the muscle, the activities of lipase, trypsin, and amylase in the intestine, as well as the relative expression levels of metallothionein (mt), cytochrome P450 1A (cyp1a), carnitine palmitoyltransferase-1 (cpt-1), peroxisome proliferator-activated receptor alpha (pparα), peroxisome proliferator-activated receptor gamma (pparγ), hormone-sensitive lipase (hsl), lipoprotein lipase (lpl), malate dehydrogenase (mdh), leptin (lep), fatty acid synthase (fas), sterol regulatory element-binding protein 1 (srebp1), and stearoyl-CoA desaturase (scd) genes in the liver of juveniles were significantly increased (p < 0.05). In conclusion, dietary chitosan supplementation could alleviate the effects of Cd2+ stress on the muscle composition, digestive enzymes, lipid metabolism, and stress resistance, and their related gene expression, of juvenile tilapia, and to some extent reduce the toxic effect of Cd2+ stress on tilapia. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the effects of aerobic treadmill training regimen of four weeks duration on oxidative stress parameters, metabolic enzymes, and histomorphometric changes in the colon of hyperhomocysteinemic rats. Male Wistar albino rats were divided into four groups (n = 10, per group): C, 0.9% NaCl 0.2 mL/day subcutaneous injection (s.c.) 2x/day; H, homocysteine 0.45 µmol/g b.w./day s.c. 2x/day; CPA, saline (0.9% NaCl 0.2 mL/day s.c. 2x/day) and an aerobic treadmill training program; and HPA, homocysteine (0.45 µmol/g b.w./day s.c. 2x/day) and an aerobic treadmill training program. The HPA group had an increased level of malondialdehyde (5.568 ± 0.872 μmol/mg protein, p = 0.0128 vs. CPA (3.080 ± 0.887 μmol/mg protein)), catalase activity (3.195 ± 0.533 U/mg protein, p < 0.0001 vs. C (1.467 ± 0.501 U/mg protein), p = 0.0012 vs. H (1.955 ± 0.293 U/mg protein), and p = 0.0003 vs. CPA (1.789 ± 0.256 U/mg protein)), and total superoxide dismutase activity (9.857 ± 1.566 U/mg protein, p < 0.0001 vs. C (6.738 ± 0.339 U/mg protein), p < 0.0001 vs. H (6.015 ± 0.424 U/mg protein), and p < 0.0001 vs. CPA (5.172 ± 0.284 U/mg protein)) were detected in the rat colon. In the HPA group, higher activities of lactate dehydrogenase (2.675 ± 1.364 mU/mg protein) were detected in comparison to the CPA group (1.198 ± 0.217 mU/mg protein, p = 0.0234) and higher activities of malate dehydrogenase (9.962 (5.752–10.220) mU/mg protein) were detected in comparison to the CPA group (4.727 (4.562–5.299) mU/mg protein, p = 0.0385). Subchronic treadmill training in the rats with hyperhomocysteinemia triggers the colon tissue antioxidant response (by increasing the activities of superoxide dismutase and catalase) and elicits an increase in metabolic enzyme activities (lactate dehydrogenase and malate dehydrogenase). This study offers a comprehensive assessment of the effects of aerobic exercise on colonic tissues in a rat model of hyperhomocysteinemia, evaluating a range of biological indicators including antioxidant enzyme activity, metabolic enzyme activity, and morphometric parameters, which suggested that exercise may confer protective effects at both the physiological and morphological levels. [ABSTRACT FROM AUTHOR]

Objective: Malate dehydrogenase (MDH, ЕC 1.1.1.37) is a multifunctional enzyme complex that catalyzes the reversible conversion of malate to oxaloacetate using NADH as a coenzyme. Currently, the regulation of MDH expression is poorly understood and needs further study. The aim of the study was to study the role of transcription factor CREB1 in regulating the expression of the gene encoding the mitochondrial form of malate dehydrogenase in the liver of rats Rattus norvegicus L. with experimental diabetes. Methods: The work investigated the rate of malate dehydrogenase functioning and the features of its regulation by the transcription factor CREB. Results and Discussion: An increase in the rate of work of NAD-dependent malate dehydrogenase in rat liver cells during the development of experimental diabetes was shown, associated with the activation of the Mdh1 and Mdh2 genes encoding this enzyme. The analysis of the promoters of these genes showed that only in the Mdh2 gene there is a specific binding site with the transcription factor CREB1. It was found that in the liver of rats with pathology, there is an increase in the rate of expression of the gene encoding this transcription factor, which correlates with the expression of the Mdh2 gene. Conclusions: Thus, the data obtained by us confirm the possibility of positive regulation of the rate of the Mdh2 gene by the transcription factor CREB1. [ABSTRACT FROM AUTHOR]

Differentiation-inducing factor 1 (DIF-1), found in Dictyostelium discoideum, has antiproliferative and glucose-uptake-promoting activities in mammalian cells. DIF-1 is a potential lead for the development of antitumor and/or antiobesity/antidiabetes drugs, but the mechanisms underlying its actions have not been fully elucidated. In this study, we searched for target molecules of DIF-1 that mediate the actions of DIF-1 in mammalian cells by identifying DIF-1-binding proteins in human cervical cancer HeLa cells and mouse 3T3-L1 fibroblast cells using affinity chromatography and liquid chromatography–tandem mass spectrometry and found mitochondrial malate dehydrogenase (MDH2) to be a DIF-1-binding protein in both cell lines. Since DIF-1 has been shown to directly inhibit MDH2 activity, we compared the effects of DIF-1 and the MDH2 inhibitor LW6 on the growth of HeLa and 3T3-L1 cells and on glucose uptake in confluent 3T3-L1 cells in vitro. In both HeLa and 3T3-L1 cells, DIF-1 at 10–40 μM dose-dependently suppressed growth, whereas LW6 at 20 μM, but not at 2–10 μM, significantly suppressed growth in these cells. In confluent 3T3-L1 cells, DIF-1 at 10–40 μM significantly promoted glucose uptake, with the strongest effect at 20 μM DIF-1, whereas LW6 at 2–20 μM significantly promoted glucose uptake, with the strongest effect at 10 μM LW6. Western blot analyses showed that LW6 (10 μM) and DIF-1 (20 μM) phosphorylated and, thus, activated AMP kinase in 3T3-L1 cells. Our results suggest that MDH2 inhibition can suppress cell growth and promote glucose uptake in the cells, but appears to promote glucose uptake more strongly than it suppresses cell growth. Thus, DIF-1 may promote glucose uptake, at least in part, via direct inhibition of MDH2 and a subsequent activation of AMP kinase in 3T3-L1 cells. [ABSTRACT FROM AUTHOR]

Wing dimorphism of insect vectors is a determining factor for viral long-distance dispersal and large-area epidemics. Although plant viruses affect the wing plasticity of insect vectors, the potential underlying molecular mechanisms have seldom been investigated. Here, we found that a planthopper-vectored rice virus, rice stripe virus (RSV), specifically induces a long-winged morph in male insects. The analysis of field populations demonstrated that the long-winged ratios of male insects are closely associated with RSV infection regardless of viral titers. A planthopper-specific and testis-highly expressed gene, Encounter, was fortuitously found to play a key role in the RSV-induced long-winged morph. Encounter resembles malate dehydrogenase in the sequence, but it does not have corresponding enzymatic activity. Encounter is upregulated to affect male wing dimorphism at early larval stages. Encounter is closely connected with the insulin/insulin-like growth factor signaling pathway as a downstream factor of Akt, of which the transcriptional level is activated in response to RSV infection, resulting in the elevated expression of Encounter. In addition, an RSV-derived small interfering RNA directly targets Encounter to enhance its expression. Our study reveals an unreported mechanism underlying the direct regulation by a plant virus of wing dimorphism in its insect vectors, providing the potential way for interrupting viral dispersal. [ABSTRACT FROM AUTHOR]

Fumaric acid is a useful unsaturated dicarboxylic acid that serves as a precursor for the biodegradable plastics poly(butylene succinate) and poly(propylene fumarate). Currently, fumaric acid is mainly synthesised from petroleum resources such as benzene. It is therefore desirable to develop methods to produce fumaric acid from renewable resources such as those derived from biomass. In this work, an effective visible-light driven fumarate production from gaseous CO2 and pyruvate with the system consisting of triethanolamine, cationic water-soluble zinc porphyrin, zinc tetrakis(4-N,N,N-trimethylaminophenyl)porphyrin, pentamethylcyclopentadienyl coordinated rhodium(III) 2,2′-bipyridyl complex, NAD+, malate dehydrogenase (NAD+-dependent oxaloacetate-decarboxylating) and fumarase was developed. [ABSTRACT FROM AUTHOR]

Retentostat cultivations have enabled investigations into substrate‐limited near‐zero growth for a number of microbes. Quantitative physiology at these near‐zero growth conditions has been widely discussed, yet characterisation of the fluxome is relatively under‐reported. We investigated the rewiring of metabolism in the transition of a recombinant protein‐producing strain of Komagataella phaffii to glucose‐limited near‐zero growth rates. We used cultivation data from a 200‐fold range of growth rates and comprehensive biomass composition data to integrate growth rate dependent biomass equations, generated using a number of different approaches, into a K. phaffii genome‐scale metabolic model. Here, we show that a non‐growth‐associated maintenance value of 0.65 mmolATPgCDW−1h−1 and a growth‐associated maintenance value of 108 mmolATPgCDW−1 lead to accurate growth rate predictions. In line with its role as energy source, metabolism is rewired to increase the yield of ATP per glucose. This includes a reduction of flux through the pentose phosphate pathway, and a greater utilisation of glycolysis and the TCA cycle. Interestingly, we observed activity of an external, non‐proton translocating NADH dehydrogenase in addition to the malate–aspartate shuttle. Regardless of the method used for the generation of biomass equations, a similar, yet different, growth rate dependent rewiring was predicted. As expected, these differences between the different methods were clearer at higher growth rates, where the biomass equation provides a much greater constraint than at slower growth rates. When placed on an increasingly limited glucose diet, the metabolism of K. phaffii adapts, enabling it to continue to drive critical processes sustaining its high viability at near‐zero growth rates. [ABSTRACT FROM AUTHOR]

Objective: Reduction of cerebral ischemia-reperfusion injury (IRI)/re-oxygenation injury, is defined as the paradoxical exacerbation of the cellular dysfunction and death, following restoration of the blood flow to previously ischemic tissues. The re-establishment of blood flow is essential to salvage the ischemic tissues. As a result, the treatment of IRI with novel therapies, which have fewer side effects, are of great importance. Therefore, this study aimed to investigate the effects of curcumin nanoparticle (CN) pre-treatment on the cerebral I/R rat model. Materials and Methods: In this experimental study, CN was administered to rats orally five days before the bilateral common carotid artery occlusion (BCCAO) and continued for three days. The intensity of oxidative stress, the activities of antioxidant enzymes, glutathione (GSH) content, the activity of mitochondrial enzymes, including succinate dehydrogenase (SDH), malate dehydrogenase (MDH) and lactate dehydrogenase (LDH), curcumin bioavailability, pERK/ERK expression ratio and TFEB protein were studied. Data analysis was performed using Graphpad Prism V.8 software, one-way analysis of variance (ANOVA) with the statistical package for the social sciences (SPSS V.26 software). Results: Cerebral IRI-damage significantly increased the oxidative stress (P=0.0008) and decreased the activity of the antioxidant enzymes including catalase (CAT) (P<0.001), super oxide dismutase (SOD) (P<0.001), reduced GSH (P<0.001), mitochondrial enzymes, pERK/ERK expression ratio (P=0.002) and TEFB protein (P=0.005) in rats’ brains. In addition, the pre-treatment of the rats with CN resulted in a decrease in the reactive oxygen species (ROS), and an increase in the activities of antioxidants and mitochondrial enzymes. This in turn up-regulated the pERK/ERK expression ratio and TEFB expression. Conclusion: CN has neuroprotective effects on the cerebral IRI condition due to its antioxidant properties and is able to overexpress the pERK and TFEB proteins; thus, it can be considered as a suitable treatment option during and after the incidence of stroke. [ABSTRACT FROM AUTHOR]

Tumour-associated angiogenesis play key roles in tumour growth and cancer metastasis. Consequently, several anti-angiogenic drugs such as sunitinib and axitinib have been approved for use as anti-cancer therapies. However, the majority of these drugs target the vascular endothelial growth factor A (VEGFA)/VEGF receptor 2 (VEGFR2) pathway and have shown mixed outcome, largely due to development of resistances and increased tumour aggressiveness. In this study, we used the zebrafish model to screen for novel anti-angiogenic molecules from a library of compounds derived from natural products. From this, we identified canthin-6-one, an indole alkaloid, which inhibited zebrafish intersegmental vessel (ISV) and sub-intestinal vessel development. Further characterisation revealed that treatment of canthin-6-one reduced ISV endothelial cell number and inhibited proliferation of human umbilical vein endothelial cells (HUVECs), suggesting that canthin-6-one inhibits endothelial cell proliferation. Of note, canthin-6-one did not inhibit VEGFA-induced phosphorylation of VEGFR2 in HUVECs and downstream phosphorylation of extracellular signal-regulated kinase (Erk) in leading ISV endothelial cells in zebrafish, suggesting that canthin-6-one inhibits angiogenesis independent of the VEGFA/VEGFR2 pathway. Importantly, we found that canthin-6-one impairs tumour-associated angiogenesis in a zebrafish B16F10 melanoma cell xenograft model and synergises with VEGFR inhibitor sunitinib malate to inhibit developmental angiogenesis. In summary, we showed that canthin-6-one exhibits anti-angiogenic properties in both developmental and pathological contexts in zebrafish, independent of the VEGFA/VEGFR2 pathway and demonstrate that canthin-6-one may hold value for further development as a novel anti-angiogenic drug. [ABSTRACT FROM AUTHOR]

In plant leaves, starch is composed of glucan polymers that accumulate in chloroplasts as the products of photosynthesis during the day; starch is mobilized at night to continuously provide sugars to sustain plant growth and development. Efficient starch degradation requires the involvement of several enzymes, including β-amylase and glucan phosphatase. However, how these enzymes cooperate remains largely unclear. Here, we show that the glucan phosphatase LIKE SEX FOUR 1 (LSF1) interacts with plastid NAD-dependent malate dehydrogenase (MDH) to recruit β-amylase (BAM1), thus reconstituting the BAM1–LSF1–MDH complex. The starch hydrolysis activity of BAM1 drastically increased in the presence of LSF1–MDH in vitro. We determined the structure of the BAM1–LSF1–MDH complex by a combination of cryo-electron microscopy, crosslinking mass spectrometry, and molecular docking. The starch-binding domain of the dual-specificity phosphatase and carbohydrate-binding module of LSF1 was docked in proximity to BAM1, thus facilitating BAM1 access to and hydrolysis of the polyglucans of starch, thus revealing the molecular mechanism by which the LSF1–MDH complex improves the starch degradation activity of BAM1. Moreover, LSF1 is phosphatase inactive, and the enzymatic activity of MDH was dispensable for starch degradation, suggesting nonenzymatic scaffold functions for LSF1–MDH in starch degradation. These findings provide important insights into the precise regulation of starch degradation. Phosphatase-inactive LIKE SEX FOUR 1 interacts with moonlighting malate dehydrogenase to form a binary complex acting as a scaffold to recruit β-amylase to promote starch degradation. [ABSTRACT FROM AUTHOR]

A photoelectrochemical biosensor for malate was developed using an indium tin oxide (ITO) layer deposited on a poly(ethylene terephthalate) plastic sheet as a transparent electrode material for the immobilization of malate dehydrogenase together with CdTe quantum dots. Different approaches were compared for the construction of the bioactive layer; the highest response was achieved by depositing malate dehydrogenase together with CdTe nanoparticles and covering it with a Nafion/water (1:1) mixture. The amperometric signal of this biosensor was recorded during irradiation with a near-UV LED in the flow-through mode. The limit of detection was 0.28 mmol/L, which is adequate for analyzing malic acid levels in drinks such as white wines and fruit juices. The results confirm that the cheap ITO layer deposited on the plastic sheet after cutting into rectangular electrodes allows for the economic production of photoelectrochemical (bio)sensors. The combination of NAD+-dependent malate dehydrogenase with quantum dots was also compatible with such an ITO surface. [ABSTRACT FROM AUTHOR]

Based on Schreiber's work on transfer entropy, a molecular theory of nonlinear information transfer between residue pairs in proteins is developed. The joint distribution function for residue fluctuations required by the theory is expressed in terms of tensor Hermite polynomials that conveniently separate harmonic and nonlinear contributions to information transfer. The harmonic part of information transfer is expressed as the difference between time dependent and independent mutual information. Third order nonlinearities are discussed in detail. The amount and speed of information transfer between residues, which are important for understanding allosteric activity in proteins, are discussed. Mutual information between two residues is commonly used for information transfer. While mutual information shows the maximum amount of information that may be transferred between two residues, it does not explain the actual amount of transfer nor the transfer rate of information. For this, dynamic equations of the system are needed. The solution of the Langevin equation and molecular dynamics trajectories are used in the present work for this purpose. Allosteric communication in human NAD-dependent isocitrate dehydrogenase is studied as an example. Calculations show that several paths contribute collectively to information transfer. Important residues on these paths are identified. Time resolved information transfer between these residues, their amplitudes, and transfer rates, which are in agreement with time resolved ultraviolet resonance Raman measurements in general, are estimated. Peak values of calculated information transfer, ∼0.01–0.04 bits, are about two orders of magnitude smaller than the information content of residues. They are comparable to mutual information values, however. Estimated transfer rates are in the order of 1–20 megabits per second, and sustained transfer during the activity time-span of proteins may be significant. Information transfer from third order contributions is one to two orders of magnitude smaller than the harmonic terms, showing that harmonic analysis is a good approximation to information transfer. [ABSTRACT FROM AUTHOR]

The plerocercoid larva of Spirometra mansoni can cause a parasitic zoonosis—sparganosis. Malate dehydrogenase (MDH) plays a very important role in the life activities of parasites. However, little is known about the MDH family in S. mansoni. We identified eight new MDH members in S. mansoni in this study. Clustering analysis divided SmMDHs into two groups and revealed patterns similar to the conserved motif organization. RT–qPCR suggested that five MDHs were highly expressed in the mature proglottid and that three MDHs were highly expressed in the gravid proglottid. Phylogenetic analysis revealed that SmMDHs contain both conserved family members and members in the process of further diversification. rSmMDH has an NAD binding domain, a dimer interface and a substrate binding domain. Natural SmMDH was immunolocalized in the tissues and follicles around the uterus in the mature or gravid proglottid and eggshells. The maximum forward and reverse reaction activities of rSmMDH were observed at pH 8.5 and 9.0, respectively. The optimum temperature for enzyme activity was 37 °C in the forward reaction and 40 °C in the reverse reaction. These results lay the foundation for studying the molecular functions and mechanisms of MDHs in S. mansoni and related taxa.

Tryptophan is a functional amino acid. This study aimed to investigate whether dietary tryptophan supplementation can alleviate Escherichia coli lipopolysaccharide (LPS)-induced skeletal muscle fiber transition from type I to type II in pigs, and the molecular mechanism was also examined. Eighteen weaned piglets were allotted to three treatments groups, namely, the nonchallenged control, LPS-challenged control and LPS + 0.2% tryptophan groups. On day 35, the pigs in the LPS and LPS + 0.2% tryptophan groups were challenged by injection with 100 μg/kg body weight (BW) LPS, whereas the control group was given sterile saline. Tryptophan can attenuate LPS-induced decrease in protein content of slow MyHC, the activities of succinic dehydrogenase, malate dehydrogenase (MDH) and antioxidant enzyme, the mRNA expression of oxidative muscle fiber-related genes, type I fiber proportion, and increase in lactate dehydrogenase (LDH) activity, the mRNA expression level of MyHC IIb and type II fiber proportion. Moreover, tryptophan supplementation attenuated LPS-induced decrease in the expression levels of phosphorylated AMP-activated protein kinase (AMPK), silent information regulator 1 (Sirt1) and peroxisome proliferator activated receptor gamma coactivator 1-alpha (PGC-1α). Collectively, tryptophan can alleviate LPS-induced muscle fiber type transformation from type I to type II. This effect is associated with activating the Sirt1/AMPK/PGC-1α signaling pathway. [ABSTRACT FROM AUTHOR]

This study investigated the effect of taurine (TAU) on the muscle fiber type transformation in porcine myoblasts and its molecular mechanisms. The findings revealed that TAU augmented the protein expression of slow MyHC and the enzyme activities of oxidative metabolism markers like malate dehydrogenase and succinic dehydrogenase. Conversely, it curtailed the expression of fast MyHC and glycolytic metabolism enzyme activity of lactate dehydrogenase. Moreover, TAU elevated the expression of genes associated with oxidative fiber while diminishing the expression of those linked to glycolytic fibers, suggesting that TAU promoted the muscle fiber type transformation from glycolytic fiber to oxidative fiber. Additionally, TAU notably enhanced the expression of key molecules of calcineurin (CaN)/nuclear factor of activated T cells c1 (NFATc1) signaling and the CaN activity in porcine myoblasts. However, CaN inhibitor cyclosporine A abolished these effects induced by TAU. Our results indicated that TAU regulated the muscle fiber type transformation from glycolytic to oxidative fiber by activation of CaN/NFATc1 signaling. [ABSTRACT FROM AUTHOR]

Melatonin is a multifunctional bioactive molecule present in almost all organisms and has been gradually used in the aquaculture industry in recent years. Energy metabolism is an essential process for individuals to maintain their life activities; however, the process through which melatonin regulates energy metabolism in aquatic animals remains unclear. The present study aimed to conduct a comprehensive analysis of the regulatory mechanism of melatonin for energy metabolism in Cherax destructor by combining metabolomics analysis with the detection of the key substance content, enzymatic activity, and gene expression levels in the energy metabolism process after culturing with dietary melatonin supplementation for 8 weeks. Our results showed that dietary melatonin increased the content of glycogen, triglycerides, and free fatty acids; decreased lactate levels; and promoted the enzymatic activity of pyruvate kinase (PK), malate dehydrogenase (MDH), and acetyl-CoA carboxylase. The results of gene expression analysis showed that dietary melatonin also increased the expression levels of hexokinase, PK, MDH, lactate dehydrogenase, lipase, and fatty acid synthase genes. The results of metabolomics analysis showed that differentially expressed metabolites were significantly enriched in lysine degradation and glycerophospholipid metabolism. In conclusion, our study demonstrates that dietary melatonin increased oxidative phosphorylation, improved glucose utilization, and promoted storage of glycogen and lipids in C. destructor. These lipids are used not only for energy storage but also to maintain the structure and function of cell membranes. Our results further add to the understanding of the mechanisms of energy regulation by melatonin in crustaceans. [ABSTRACT FROM AUTHOR]

Malate dehydrogenase (MDH; EC 1.1.1.37) plays a vital role in plant growth and development as well as abiotic stress responses, and it is widely present in plants. However, the MDH family genes have not been explored in sweet potato. In this study, nine, ten, and ten MDH genes in sweet potato (Ipomoea batatas) and its two diploid wild relatives, Ipomoea trifida and Ipomoea triloba, respectively, were identified. These MDH genes were unevenly distributed on seven different chromosomes among the three species. The gene duplications and nucleotide substitution analysis (Ka/Ks) revealed that the MDH genes went through segmental duplications during their evolution under purifying selection. A phylogenetic and conserved structure divided these MDH genes into five subgroups. An expression analysis indicated that the MDH genes were omni-presently expressed in distinct tissues and responded to various abiotic stresses. A transcription factor prediction analysis proved that Dof, MADS-box, and MYB were the main transcription factors of sweet potato MDH genes. These findings provide molecular features of the MDH family in sweet potato and its two diploid wild relatives, which further supports functional characterizations. [ABSTRACT FROM AUTHOR]

Malate dehydrogenase (MDH) is one kind of oxidation–reduction enzyme that catalyzes the reversible conversion of oxaloacetic acid to malic acid. It has vital functions in plant development, photosynthesis, abiotic stress responses, and so on. However, there are no reports on the genome-wide identification and gene expression of the MDH gene family in Arachis hypogaea. In this study, the MDH gene family of A. hypogaea was comprehensively analyzed for the first time, and 15 AhMDH sequences were identified. According to the phylogenetic tree analysis, AhMDHs are mainly separated into three subfamilies with similar gene structures. Based on previously reported transcriptome sequencing results, the AhMDH expression quantity of roots and leaves exposed to manganese (Mn) toxicity were explored in A. hypogaea. Results revealed that many AhMDHs were upregulated when exposed to Mn toxicity, suggesting that those AhMDHs might play an important regulatory role in A. hypogaea's response to Mn toxicity stress. This study lays foundations for the functional study of AhMDHs and further reveals the mechanism of the A. hypogaea signaling pathway responding to high Mn stress. [ABSTRACT FROM AUTHOR]

The effect of moderate hypoxia on the processes of energy metabolism was studied in the tissues (gills, hepatopancreas) of the Mediterranean mussel Mytilus galloprovincialis (Lamarck, 1819). The mollusks was kept at 6.8–6.9 mg O2 L–1 (control group) or 1.9–2.0 mg O2 L–1 (experimental group). In both cases, water temperature was 22 ± 1°C, salinity 17–18‰, exposure time 72 h. Dissolved oxygen content in water was lowered by nitrogen bubbling for 4–5 h. Under moderately hypoxic conditions, a complex of biochemical reactions aimed at retaining the baseline energy status developed in the mussel tissues. While aerobic processes were clearly on the decline, as evidenced by a decrease in succinate dehydrogenase (SDH) activity, anaerobic glycolysis intensified. Aldolase and malate dehydrogenase (MDH) activities, as well as tissue pyruvate level, increased. Both lactate dehydrogenase (LDH) activity and lactate levels in mussel tissues remained unchanged. The state of the M. galloprovincialis adenylate system was comprehensively characterized. The tissue content of the ATP fraction remained at the level of control values, reflecting an adaptive trend in the reorganization of tissue metabolism. The ability of the hepatopancreas to accumulate ADP and AMP fractions from the circulatory systems under conditions of experimental hypoxic load was noted for the first time. Presumably, this may largely explain the increase in the pool of adenylates and the decrease in the adenylate energy charge in this organ. It was concluded that the reorganization of carbohydrate metabolism in M. galloprovincialis under moderately hypoxic conditions allows the mussel to retain the energy status of its tissues and, therefore, to populate challenging (hypoxic) waters. [ABSTRACT FROM AUTHOR]

Altered hepatic mitochondrial fatty acid β-oxidation and associated tricarboxylic acid (TCA) cycle activity contributes to lifestyle-related diseases, and circulating biomarkers reflecting these changes could have disease prognostic value. This study aimed to determine hepatic and systemic changes in TCA-cycle-related metabolites upon the selective pharmacologic enhancement of mitochondrial fatty acid β-oxidation in the liver, and to elucidate the mechanisms and potential markers of hepatic mitochondrial activity. Male Wistar rats were treated with 3-thia fatty acids (e.g., tetradecylthioacetic acid (TTA)), which target mitochondrial biogenesis, mitochondrial fatty acid β-oxidation, and ketogenesis predominantly in the liver. Hepatic and plasma concentrations of TCA cycle intermediates and anaplerotic substrates (LC-MS/MS), plasma ketones (colorimetric assay), and acylcarnitines (HPLC-MS/MS), along with associated TCA-cycle-related gene expression (qPCR) and enzyme activities, were determined. TTA-induced hepatic fatty acid β-oxidation resulted in an increased ratio of plasma ketone bodies/nonesterified fatty acid (NEFA), lower plasma malonyl-CoA levels, and a higher ratio of plasma acetylcarnitine/palmitoylcarnitine (C2/C16). These changes were associated with decreased hepatic and increased plasma pyruvate concentrations, and increased plasma concentrations of succinate, malate, and 2-hydroxyglutarate. Expression of several genes encoding TCA cycle enzymes and the malate–oxoglutarate carrier (Slc25a11), glutamate dehydrogenase (Gdh), and malic enzyme (Mdh1 and Mdh2) were significantly increased. In conclusion, the induction of hepatic mitochondrial fatty acid β-oxidation by 3-thia fatty acids lowered hepatic pyruvate while increasing plasma pyruvate, as well as succinate, malate, and 2-hydroxyglutarate. [ABSTRACT FROM AUTHOR]

Diabetic peripheral neuropathy (DPN) is the prevalent type of peripheral neuropathy; it primarily impacts extremity nerves. Its multifaceted nature makes the molecular mechanisms of diabetic neuropathy intricate and incompletely elucidated. Several types of post-translational modifications (PTMs) have been implicated in the development and progression of DPN, including phosphorylation, glycation, acetylation and SUMOylation. SUMOylation involves the covalent attachment of small ubiquitin-like modifier (SUMO) proteins to target proteins, and it plays a role in various cellular processes, including protein localization, stability, and function. While the specific relationship between high blood glucose and SUMOylation is not extensively studied, recent evidence implies its involvement in the development of DPN in type 1 diabetes. In this study, we investigated the impact of SUMOylation on the onset and progression of DPN in a type 2 diabetes model using genetically modified mutant mice lacking SUMOylation, specifically in peripheral sensory neurons (SNS-Ubc9−/−). Behavioural measurement for evoked pain, morphological analyses of nerve fibre loss in the epidermis, measurement of reactive oxygen species (ROS) levels, and antioxidant molecules were analysed over several months in SUMOylation-deficient and control mice. Our longitudinal analysis at 30 weeks post-high-fat diet revealed that SNS-Ubc9−/− mice exhibited earlier and more pronounced thermal and mechanical sensation loss and accelerated intraepidermal nerve fibre loss compared to control mice. Mechanistically, these changes are associated with increased levels of ROS both in sensory neuronal soma and in peripheral axonal nerve endings in SNS-Ubc9−/− mice. In addition, we observed compromised detoxifying potential, impaired respiratory chain complexes, and reduced levels of protective lipids in sensory neurons upon deletion of SUMOylation in diabetic mice. Importantly, we also identified mitochondrial malate dehydrogenase (MDH2) as a SUMOylation target, the activity of which is negatively regulated by SUMOylation. Our results indicate that SUMOylation is an essential neuroprotective mechanism in sensory neurons in type 2 diabetes, the deletion of which causes oxidative stress and an impaired respiratory chain, resulting in energy depletion and subsequent damage to sensory neurons. [ABSTRACT FROM AUTHOR]

Background: The present investigation was envisaged to find out the impact of extreme hot environmental temperature period (ETP) on marker enzymes of carbohydrate metabolism in male and female non-descript sheep of various age groups i.e. 4 to 13 months from arid tracts of Rajasthan. Glucose-6-phosphate dehydrogenase (G-6-PDH) and malate dehydrogenase (MDH) marker enzymes of carbohydrate metabolism were considered for study. Methods: During the period October 2016-June 2017 blood samples were collected to harvest sera for spectrophotometric method from 240 healthy animals selected from private slaughter house during moderate and extreme hot environmental temperature periods (ETPs). The mean values of markers attained during moderate ETP were reckoned as the control. It was 10.00±0.10 UL-1 and 42.00±1.00 respectively. Conclusion: The mean value of MDH was significantly (p≤0.05) higher while G-6-PDH significantly (p≤0.05) lowers during extreme hot temperature in comparison to moderate period. Therefore, it could be concluded that variations in enzyme markers were associated with changes in environmental temperatures. Probably ETP were able to produce a profound effect on carbohydrate metabolism in sheep. Therfore it can be suggested that during the period of extreme temperature balanced ration must be provided to the animal along with proper management to decrease the severity of temperature impact. [ABSTRACT FROM AUTHOR]

The COVID-19 outbreak has had a significant impact on higher education worldwide. In-person courses had to be quickly transited to online, including lab courses embedded with Course-based Undergraduate Research Experiences (CUREs). In response to this challenge, we successfully converted a fully in-person biochemistry lab that integrated with a 6-week modular CURE (mCURE) into a hybrid CURE (hCURE) in Fall 2020, with support from the Malate dehydrogenase CUREs Community. The hCURE was structured to have in-person labs and online activities arranged on an alternating weekly basis, so that only half of the regular class size of students attended the hands-on labs at any given time to maintain proper social distancing. To evaluate the efficacy of the hCURE, student science self-efficacy and conceptual understanding of protein structure–function relationships were measured using pre-course and post-course surveys and tests, respectively. Our data showed a significant increase in student science self-efficacy and conceptual knowledge test scores. Furthermore, we compared the pre-lab quiz scores that assessed various biochemical concepts and skills across three different semesters, Fall 2019 with a fully in-person mCURE before the pandemic, Fall 2020 with the hCURE implemented during the pandemic, and Fall 2021 when the lab returned to the fully in-person mCURE following the pandemic. A significant decline in quiz scores from Fall 2019 to Fall 2020, and an even further decline from Fall 2019 to Fall 2021 were observed, suggesting that apart from the impact of course modality, the pandemic may have exerted a lasting adverse effect on student learning. [ABSTRACT FROM AUTHOR]

NAD-dependent malic enzymes catalyze NAD reduction to NADH while converting malate to pyruvate and CO 2. In this study, NAD was reduced to NADH by MaeA, NAD-dependent malic enzyme from Escherichia coli , when fumarate was used as substrate. This suggested that MaeA catalyzed the conversion of fumarate to malate and then malate to pyruvate. The K 0.5 value for fumarate was determined as 13 mM, different from previously characterized fumarases in Escherichia coli. Fumarate inhibited the malic enzyme activity of MaeA where NAD reduction to NADH was examined in the presence of malate as substrate. Human ME2, an NAD-dependent malic enzyme, also converted NAD to NADH in the presence of fumarate, suggesting that the duplex activity as fumarase and malic enzyme might be conserved in various NAD-dependent malic enzymes. MaeB, NADP-dependent malic enzyme from Escherichia coli , did not reduce NADP to NADPH in the presence of fumarate, suggesting the fumarase activities of MaeA and ME2 were specific. • NAD-dependent malic enzymes, MaeA and ME2, catalyze the reduction of NAD to NADH in the presence of fumarate. • In addition to as malic enzymes, MaeA and ME2 may function as fumarases. • Fumarate also acts an allosteric inhibitor for MaeA. [ABSTRACT FROM AUTHOR]