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The purpose of this study was to develop an effective and non-invasive nomogram for evaluating liver obvious inflammation in untreated HBeAg positive patients with chronic hepatitis B virus (HBV) infection. A nomogram was established on a model cohort of 292 treatment-naïve HBeAg positive patients with normal alanine aminotransferase (ALT ≤40 U/L) at Beijing Ditan Hospital from January 2008 to March 2018. Then the nomogram was prospectively validated in a cohort of 88 patients from July 2019 to May 2021. Calibration curves and Concordance index were used to evaluate the accuracy of prediction and identification performance of the model. In untreated HBeAg positive chronic hepatitis B virus infection patients with normal ALT, the formula for predicting liver inflammation was Logit (P) =-0.91-0.41×log 10 (qHBeAg)+0.11×AST-0.01×PLT. The nomogram had C-index of 0.751 (95% CI, 0.688-0.815), indicating a good consistency between prediction and real observation on the model cohort. The validation cohort confirmed its good performance. In this study, liver inflammation nomograms based on HBeAg, AST, and PLT were established and verified in treatment-naïve HBeAg positive chronic HBV patients with normal ALT.

Background: Osteoporosis is an extrahepatic complication of primary biliary cholangitis (PBC) that increases the risk of fractures and mortality. However, Epidemiological studies of osteoporosis in patients with PBC in China and the Asia-Pacific region is lack., Aim: To assess the prevalence and clinical characteristics of osteoporosis in Chinese patients with PBC., Methods: This retrospective analysis included consecutive patients with PBC from a tertiary care center in China who underwent bone mineral density (BMD) assessment using dual-energy X-ray absorptiometry between January 2013 and December 2021. We defined subjects with T-scores ≤ -2.5 in any sites (L1 to L4, femoral neck, or total hip) as having osteoporosis. Demographic, serological, clinical, and histological data were collected. Independent risk factors for osteoporosis were identified by multivariate logistic regression analysis., Results: A total of 268 patients with PBC [236 women (88.1%); mean age, 56.7 ± 10.6 years; 163 liver biopsies (60.8%)] were included. The overall prevalence of osteoporosis in patients with PBC was 45.5% (122/268), with the prevalence of osteoporosis in women and men being 47.0% and 34.4%, respectively. The prevalence of osteoporosis in postmenopausal women was significantly higher than that in premenopausal women (56.3% vs 21.0%, P < 0.001). Osteoporosis in patients with PBC is associated with age, fatigue, menopausal status, previous steroid therapy, body mass index (BMI), splenomegaly, gastroesophageal varices, ascites, Mayo risk score, histological stage, alanine aminotransferase, albumin, bilirubin, platelet and prothrombin activity. Multivariate regression analysis identified that older age, lower BMI, previous steroid therapy, higher Mayo risk score, and advanced histological stage as the main independent risk factors for osteoporosis in PBC., Conclusion: Osteoporosis is very common in Chinese patients with PBC, allowing for prior screening of BMD in those PBC patients with older age, lower BMI, previous steroid therapy and advanced liver disease., Competing Interests: Conflict-of-interest statement: We have no financial relationships to disclose., (©The Author(s) 2023. Published by Baishideng Publishing Group Inc. All rights reserved.)

The insecticidal activity is the result of a series of complex interactions between toxic substances as ligands and insect's enzymes as targets. Actually, synthetic insecticides used in pest control programs are harmful to the environment and may affect non-target organisms; thus, the use of natural products as pest control agents can be very attractive. In the present work, the toxic effect of aniseed ( Pimpinella anisum L.) essential oil (EO) and its nanoemulsion (NE) against the red flour beetle Tribolium castaneum , has been evaluated. To assess the EO mode of action, the impact of sub-lethal concentrations of aniseed EO and NE was evaluated on enzymatic and macromolecular parameters of the beetles, including aspartate aminotransferase (AST), alanine aminotransferase (ALT), total protein, total lipids and glucose. Finally, a molecular docking study was conducted to predict the mode of action of the major EO and NE components namely E -anethole, Limonene, alpha-himalachalene, trans-Verbenol and Linalool at binding site of the enzymes AST and ALT. Herein, the binding location of the main compounds in both proteins are discussed suggesting the possible interactions between the considered enzymes and ligands. The obtained results open new horizons to understand the evolution and response of insect-plant compounds interactions and their effect predicted at the molecular levels and side effects of both animal and human.

We report a novel approach for magneto-controlled activation of an artificial electro-enzymatic cascade. The input signal triggers release of a caged ligand peptide, its proteolytic processing and activation of an artificial allosteric enzyme based on PQQ-dependent glucose dehydrogenase. The developed cascade was used to assemble a magneto-controlled biofuel cell.

Quantum dots (QDs) are engineered nanoparticles (NPs) of semiconductor structure that possess unique optical and electronic properties and are widely used in biomedical applications; however, their risks are not entirely understood. This study investigated the tissue distribution and toxic effects of cadmium telluride quantum dots (CdTe-QDs) in male BALB/c mice for up to 1 week after single-dose intravenous injections. CdTe-QDs were detected in the blood, lung, heart, liver, spleen, kidney, testis and brain. Most CdTe-QDs accumulated in the liver, followed by the spleen and kidney. At high doses, exposure to CdTe-QDs resulted in mild dehydration, lethargy, ruffled fur, hunched posture, and body weight loss. Histological analysis of the tissues, upon highest dose exposures, revealed hepatic hemorrhage and necrotic areas in the spleen. The sera of mice treated with high doses of CdTe-QDs showed significant increases in alanine aminotransferase (ALT), aspartate aminotransferase (AST), and total bilirubin levels, as well as a reduction in albumin. CdTe-QD exposure also led to a reduced number of platelets and elevated total white blood cell counts, including monocytes and neutrophils, serum amyloid A, and several pro-inflammatory cytokines. These results demonstrated that the liver is the main target of CdTe-QDs and that exposure to CdTe-QDs leads to hepatic and splenic injury, as well as systemic effects, in mice. By contrast, cadmium chloride (CdCl 2 ), at an equivalent concentration of cadmium, appeared to have a different pharmacokinetic pattern from that of CdTe-QDs, having minimal effects on the aforementioned parameters, suggesting that cadmium alone cannot fully explain the toxicity of CdTe-QDs.

Epoxiconazole (EPX) is a triazole fungicide commonly used in agriculture and for domestic purposes around the world. The excessive application of this pesticide may result in a variety of adverse effects on non-target organisms, including humans. Since, the liver and kidneys are the target organs of this fungicide, potential hepatotoxic and nephrotoxic effects are of high relevance. Thus, our study aimed to investigate the toxic effects of EPX on the liver and kidney of Wistar rats. The exposure of rats to EPX at these concentrations (8, 24, 40, 56 mg/kg bw representing, respectively, NOEL (no observed effect level), NOEL × 3, NOEL × 5, and NOEL × 7) for 28 days significantly enhances hepatic and renal lipid peroxidation which is accompanied by an increase in the level of protein oxidation. Furthermore, the results of the present study clearly indicated that EPX administration induces an increase in the levels of DNA damage in a dose-dependent manner. In addition, the activities of liver and kidney antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione S-transferase (GST) are increased significantly in EPX-treated rats at concentrations of 8, 24, and 40 mg/kg bw. However, with the dose NOEL × 7 (56 mg/kg bw of EPX), the activities of CAT, GPx, and GST are decreased. Indeed, EPX-intoxicated rats revealed a significant reduction in acetylcholinesterase (AChE) activity in both liver and kidney compared with the control group. Also, our results demonstrated that the EPX administration leads to a disruption of the hepatic (aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), and lactate dehydrogenase (LDH)) and renal (uric acid and creatinine) functions. The biochemical perturbations obtained in the present study are corroborated with the histopathological modifications. Since EPX treatment caused severe damage in the overall histo-architecture of liver and kidney tissues, these results suggest that administration of EPX induced a marked deregulation of liver and kidney functions. Graphical abstract.

Utilizing block copolymers as coatings, a protocol of chiral ligand exchange capillary electrochromatography (CLE-CEC) protocol was designed and developed with dual ligands for D,L-amino acids enantioseparation. Four block copolymers including poly maleic anhydride-co-styrene-co-N-methacryloyl-L-histidine methyl ester [P(MAn-St-MAH)], poly maleic anhydride-co-styrene-co-N-methacryloyl-L-lysine methyl ester [P(MAn-St-MAL)], poly maleic anhydride-co-styrene-co-N-methacryloyl-L-phenylalanine methyl ester [P(MAn-St-MAP)] and poly maleic anhydride-co-styrene-co-N-methacryloyl-L-threonine methyl ester [P(MAn-St-MAT)] were synthesized by reversible addition fragmentation chain transfer polymerization reaction. Key factors affecting the enantioresolution were optimized, including the concentration of Zn (II) central ion, pH value of buffer solution and monomers of the block copolymers. The enantioresolution of the proposed CLE-CEC system could be enhanced dramatically by employing P(MAn-St-MAH) as the immobilized chiral ligand and by coordinating the synergistic effect of free ligand in buffer solution. The principle of improved enantioresolution of the CLE-CEC system with dual ligands was discussed. Well enantioseparation was successfully realized with 7 pairs of D,L-amino acids enantiomers baseline separation and 5 pairs part separation. For quantitative analysis of D,L-alanine, a good linearity was established in the range of 9.4 μM to 1.5 mM (r 2 = 0.997) with the limits of detection (LODs) 3.7 μM of D-alanine, 2.0 μM for L-alanine, and limits of quantification (LOQs) 9.0 μM for D-alanine and 6.0 μM for L-alanine. The peak area and migration time reproducibility (n = 6) were 4.1% and 3.5% for D-alanine, 3.7% and 3.1% for L-alanine. Further, the enzyme kinetics study of alanine aminotransferase was investigated with the constructed CLE-CEC system., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The aim of the study was to establish normal ranges for chosen biochemical parameters of haemolymph of snails (Gasropoda: Mollusca), in the light of the use of these animals as experi- mental models in various types of studies. The study was conducted on 100 specimens of Cornu aspersum maxima (CAM) and 100 specimens of Cepaea nemoralis (CN). The haemolymph col- lected from the animals was analysed using colorimetry to assay aspartate transaminase (AST) activity, alanine transaminase (ALT) activity, amylase activity and the concentrations of urea and triglycerides. In the further part of the study, the influence of administering doxycycline with feed on the change of AST and ALT activity in snail haemolymph has been studied. The normal values established for CAM are as follow: AST activity: 26-38 u/l, ALT activity: 0-11 u/l, amylase activity 9-16 u/l, concentration of urea: 3-6 mg/dl, concentration of triglycerides: 16-20 mg/dl. For CN, the following data have been obtained: AST activity: 30-80 u/l, ALT activity: 0-15 u/l, amylase activity 12-15 u/l, concentration of urea: 5-8 mg/dl, concentration of triglycerides: 18-24 mg/dl. It has been shown that doxycycline presents a high workload on the hepatopancreas of snails, which is reflected by a statistically significant (p ⟨ 0.05) increase of AST and ALT activity in the haemolymph of the specimens which obtained doxycycline in feed, as compared to the groups with antibiotic-free feed. The haemolymph activity of both studied parameters increased together with study time and tetracycline administration time., (Copyright© by the Polish Academy of Sciences.)

Cyanobacterial proliferation in river and lakes is the result of eutrophication. The cyanobacterium Radiocystis fernandoi strain R28 produces mostly two MC variants MC-RR and MC-YR and small amounts of other oligopeptides, but does not produce MC-LR. The present study investigated the hepatotoxic potential of the crude extract of the R. fernandoi strain R28 on the Neotropical fish, Piaractus mesopotamicus, at 3, 6, and 24 h after intraperitoneal injection (100 μg MC-LR equivalent per kg -1 body mass) using biochemical and morphological biomarkers of liver damage. Although the protein phosphatases PP1 and PP2A were not inhibited during the 24-h treatment, liver parenchyma and hepatocyte structure were disrupted. Alkaline phosphatase increased at 3 h post-injection and decreased after 24 h; alanine aminotransferase and aspartate aminotransferase increased in a time-dependent manner up to 24 h indicating impaired liver function. Progressive histopathological changes were consistent with biochemical results demonstrating alterations in liver structure and function. In conclusion, the crude extract of R. fernandoi strain R28 has high hepatotoxic potential and can severely compromise fish health.

Alanine aminotransferase (ALT) plays significant role in biological and clinical research. In this study, a unique ALT enzyme reactor based on multifunctional polymer@magnetic nanoparticles has been constructed for the first time and the enzymolysis efficiency has been evaluated by chiral ligand exchange capillary electrophoresis technique. Poly(N-acryloxysuccinimide) has been synthesized by reversible addition-fragmentation chain transfer polymerization method and immobilized on the magnetic nanoparticles via the succinimide group in the polymer. Interestingly, the enzyme also could easily react with the succinimide group, which enables of ALT covalent bonding onto the polymer. The enzyme amount immobilized and the immobilization time have been investigated. Comparing with free ALT in solution (V max of free enzyme = 0.6 mM min -1 ), the resultant enzyme reactor has exhibited good reusability and stability, and displayed about five times enhanced enzymolysis efficiency with L-alanine as the substrate (V max of enzyme reactor = 3.4 mM min -1 ). Furthermore, the prepared enzyme reactor has been applied in ALT inhibitors screening. The enzyme reactors based on the multifunctional polymer@magnetic nanoparticles have depicted great potential in anti-liver drugs development, liver diseases study and ALT related biological process inspect., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Several (R)-selective ω-aminotransferases (R-ωATs) have been reported. The existence of additional R-ωATs having different sequence characteristics from previous ones is highly expected. In addition, it is generally accepted that R-ωATs are variants of aminotransferase group III. Based on these backgrounds, sequences in RefSeq database were scored using family profiles of branched-chain amino acid aminotransferase (BCAT) and d-alanine aminotransferase (DAT) to predict and identify putative R-ωATs. Sequences with two profile analysis scores were plotted on two-dimensional score space. Candidates with relatively similar scores in both BCAT and DAT profiles (i.e., profile analysis score using BCAT profile was similar to profile analysis score using DAT profile) were selected. Experimental results for selected candidates showed that putative R-ωATs from Saccharopolyspora erythraea (R-ωAT&#95;Sery), Bacillus cellulosilyticus (R-ωAT&#95;Bcel), and Bacillus thuringiensis (R-ωAT&#95;Bthu) had R-ωAT activity. Additional experiments revealed that R-ωAT&#95;Sery also possessed DAT activity while R-ωAT&#95;Bcel and R-ωAT&#95;Bthu had BCAT activity. Selecting putative R-ωATs from regions with similar profile analysis scores identified potential R-ωATs. Therefore, R-ωATs could be efficiently identified by using simple family profile analysis and exploring evolutionary sequence space., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Recent studies have demonstrated that selenium (Se) and selenium nanoparticles (Se-NPs) exhibited toxicity at a higher concentration. The lethal concentration of Se and Se-NPs was estimated as 5.29 and 3.97 mg/L at 96 h in Pangasius hypophthalmus. However, the effect of different definite concentration of Se (4.5, 5.0, 5.5, and 6.0 mg/L) and Se-NPs (2.5, 3.0, 3.5, and 4.0 mg/L) was decided for acute experiment. Selenium and Se-NPs alter the biochemical attributes such as anti-oxidative status [catalase (CAT), superoxide dismutase (SOD), and glutathione-S-transferase (GST) activities], neurotransmitter enzyme, cellular metabolic enzymes, stress marker, and histopathology of P. hypophthalmus in a dose- and time-dependent manner. CAT, SOD, and GST were significantly elevated (p < 0.01) when exposed to Se and Se-NPs, and similarly, a neurotransmitter enzyme (acetylcholine esterase (AChE)) was significantly inhibited in a time- and dose-dependent manner. Further, aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, and malate hydrogenase were noticeably (p < 0.01) affected by Se and Se-NPs from higher concentration to lower concentration. Stress markers such as cortisol and HSP 70 were drastically enhanced by exposure to Se and Se-NPs. All the cellular metabolic and stress marker parameters were elevated which might be due to hyperaccumulation of Se and Se-NPs in the vital organ and target tissues. The histopathology of liver and gill was also altered such as large vacuole, cloudy swelling, focal necrosis, interstitial edema, necrosis in liver, and thickening of primary lamellae epithelium and curling of secondary lamellae due to Se and Se-NP exposure. The study suggested that essential trace element in both forms (inorganic and nano) at higher concentration in acute exposure of Se and Se-NPs led to pronounced deleterious alteration on histopathology and cellular and metabolic activities of P. hypophthalmus.

The gold nanorods (GNRs) and silver nanorods (SNRs) are utilized in various types of industrial and commercial applications. But, there is limited availability of extra pulmonary toxicity data regarding these nanorods. The present investigation evaluated the extra pulmonary toxicity induced by 10 and 25 nm GNRs and SNRs in rats following intra tracheal instillation. The serum biochemical analysis results have shown elevated levels of serum alanine transaminase (ALT) and serum creatinine following 1 day and 1 week post instillation. GNRs have shown greatly increased serum ALT levels at 1 day, 1 week and 1 month post exposure periods compared to SNRs and quartz (QTZ) treated rats. In case of serum creatinine levels, both GNRs and SNRs have shown similar elevated levels. Histopathology studies of rat liver tissues following exposure of GNRs and SNRs displayed that congestion of central vein, shrinkage and ballooning of hepatocytes and lymphocytic infiltration leading to degeneration after 1 week and 1 month post instillation periods. The histopathology of rat kidney tissue was showed tubular dilation, degeneration and necrosis with 10 nm SNRs and 10 nm GNRs after 1 month post instillation period. The 10 nm GNRs and SNRs have shown great changes in serum biochemical analysis and histopathological studies compared to 25 nm test nanorods. These observations suggest the size and dose dependent translocation and extra pulmonary toxicity of both GNRs and SNRs., Competing Interests: Conflict of interest: The authors declare that there are no conflicts of interest., (© Georg Thieme Verlag KG Stuttgart · New York.)

Aminotransferases are an important group of enzymes that catalyze the transfer of an amino group of an amino acid into a keto acid. Alanine aminotransferase from Trypanosoma cruzi (TcALAT) was cloned, overexpressed and purified. Far-UV Circular Dichroism (CD), Dynamic Light Scattering (DLS), Analytical Size Exclusion Chromatography (aSEC) and Small Angle X-ray Scattering (SAXS) provide data concerning TcALAT biophysical behavior. CD analysis displayed a typical spectrum of α-β proteins analogously as observed for other alanine aminotransferases. The protein is stable until 40oC and above that temperature starts to denatured. Its temperature of melting is equal to 50oC. DLS, aSEC and SAXS data show that protein is monomeric in solution. All these gather initial information on secondary and quaternary structures of TcALAT.

Background: Alanine transaminase (ALT) plays an important role in gluconeogenesis by converting alanine into pyruvate for glucose production. Early studies have shown that ALT activities are upregulated in gluconeogenic conditions and may be implicated in the development of diabetes. ALT consists of two isoforms, ALT1 and ALT2, with distinctive subcellular and tissue distributions. Whether and how they are regulated are largely unknown., Methods: By using Western blotting analysis, we measured hepatic ALT isoforms at the protein level in obese and diabetic animals and in Fao hepatoma cells treated with dexamethasone and insulin. In addition, we measured glucose output in Fao cells over-expressing ALT1 and ALT2., Results: Both ALT isoforms in the liver were increased in diabetic Goto-Kakizaki rats and during fasting. However, in ob/ob mice, only ALT2, but not ALT1, protein levels were elevated, and the increase of ALT2 was correlated with that of ALT activity. We further demonstrated that, in vitro, both ALT1 and ALT2 were induced by glucocorticoid dexamethasone, but suppressed by insulin in Fao cells. Finally, we showed that the over-expression of ALT1 and ALT2 in Fao cells directly increased glucose output., Conclusions: We have shown the similarity and difference in the regulation of ALT isoforms in gluconeogenic conditions at the protein level, supporting that ALT isoenzymes play an important role in glucose metabolism and may be implicated the development of insulin resistance and diabetes., (Copyright © 2015 John Wiley & Sons, Ltd.)

Enzyme design is an important area of ongoing research with a broad range of applications in protein therapeutics, biocatalysis, bioengineering, and other biomedical areas; however, significant challenges exist in the design of enzymes to catalyze specific reactions of interest. Here, we develop a computational protocol using an approach that combines molecular dynamics, docking, and MM-GBSA scoring to predict the catalytic activity of enzyme variants. Our primary focuses are to understand the molecular basis of substrate recognition and binding in an S-stereoselective ω-aminotransferase (ω-AT), which naturally catalyzes the transamination of pyruvate into alanine, and to predict mutations that enhance the catalytic efficiency of the enzyme. The conversion of (R)-ethyl 5-methyl-3-oxooctanoate to (3S,5R)-ethyl 3-amino-5-methyloctanoate in the context of several ω-AT mutants was evaluated using the computational protocol developed in this work. We correctly identify the mutations that yield the greatest improvements in enzyme activity (20-60-fold improvement over wild type) and confirm that the computationally predicted structure of a highly active mutant reproduces key structural aspects of the variant, including side chain conformational changes, as determined by X-ray crystallography. Overall, the protocol developed here yields encouraging results and suggests that computational approaches can aid in the redesign of enzymes with improved catalytic efficiency.

In order to maintain proper cellular function, the metabolism of the bacterial microbiota presents several mechanisms oriented to keep a correctly balanced amino acid pool. Central components of these mechanisms are enzymes with alanine transaminase activity, pyridoxal 5'-phosphate-dependent enzymes that interconvert alanine and pyruvate, thereby allowing the precise control of alanine and glutamate concentrations, two of the most abundant amino acids in the cellular amino acid pool. Here we report the 2.11-Å crystal structure of full-length AlaA from the model organism Escherichia coli, a major bacterial alanine aminotransferase, and compare its overall structure and active site composition with detailed atomic models of two other bacterial enzymes capable of catalyzing this reaction in vivo, AlaC and valine-pyruvate aminotransferase (AvtA). Apart from a narrow entry channel to the active site, a feature of this new crystal structure is the role of an active site loop that closes in upon binding of substrate-mimicking molecules, and which has only been previously reported in a plant enzyme. Comparison of the available structures indicates that beyond superficial differences, alanine aminotransferases of diverse phylogenetic origins share a universal reaction mechanism that depends on an array of highly conserved amino acid residues and is similarly regulated by various unrelated motifs. Despite this unifying mechanism and regulation, growth competition experiments demonstrate that AlaA, AlaC and AvtA are not freely exchangeable in vivo, suggesting that their functional repertoire is not completely redundant thus providing an explanation for their independent evolutionary conservation.

Measurement of serum alanine aminotransferase (ALT) is a common, readily available, and inexpensive laboratory assay in clinical practice. ALT activity is not only measured to detect liver disease, but also to monitor overall health. ALT activity is influenced by various factors, including viral hepatitis, alcohol consumption, and medication. Recently, the impact of metabolic abnormalities on ALT variation has raised concern due to the worldwide obesity epidemic. The normal ranges for ALT have been updated and validated considering the metabolic covariates in the various ethnic districts. The interaction between metabolic and demographic factors on ALT variation has also been discussed in previous studies. In addition, an extremely low ALT value might reflect the process of aging, and frailty in older adults has been raised as another clinically significant feature of this enzyme, to be followed with additional epidemiologic investigation. Timely updated, comprehensive, and systematic introduction of ALT activity is necessary to aid clinicians make better use of this enzyme.

Phosphohydroxylysinuria has been described in two patients with neurological symptoms, but the deficient enzyme or mutated gene has never been identified. In the present work, we tested the hypothesis that this condition is due to mutations in the AGXT2L2 gene, recently shown to encode phosphohydroxylysine phospholyase. DNA analysis from a third patient, without neurological symptoms, but with an extreme hyperlaxicity of the joints, shows the existence of two mutations, p. Gly240Arg and p.Glu437Val, both in the heterozygous state. Sequencing of cDNA clones derived from fibroblasts mRNA indicated that the two mutations were allelic. Both mutations replace conserved residues. The mutated proteins were produced as recombinant proteins in Escherichia coli and HEK293T cells and shown to be very largely insoluble, whereas the wild-type one was produced as a soluble and active protein. We conclude that phosphohydroxylysinuria is due to mutations in the AGXT2L2 gene and the resulting lack of activity of phosphohydroxylysine phospholyase in vivo. The finding that the nul alleles of p.Gly240Arg and p.Glu437Val are present at low frequencies in the European and/or North American population suggests that this condition is more common than previously thought. The diversity of the clinical symptoms described in three patients with phosphohydroxylysinuria indicates that this is most likely not a neurometabolic disease.

Hepatitis B virus (HBV) infection models and anti-HBV infection therapy models have been set up to understand and explain clinical phenomena. Many of these models have been proposed based on Zeuzem et al. and Nowak et al.'s basic virus infection model (BVIM). Some references have pointed out that the basic infection reproductive number of the BVIM is biologically questionable and gave the modified models with standard mass action incidences. This study describes one anti-HBV therapy immune model with alanine aminotransferase (ALT) based on standard mass action incidences. There are two basic infection reproductive numbers R0 and R1 in the model. It is proved that if R0 < 1 and R1 < 1, the disease free equilibrium is locally and globally asymptotically stable, respectively. For the endemic equilibrium, simulation shows that if R1 > 1, it may be also globally asymptotically stable. Simulations based on clinical data of HBV DNA and ALT can explain some clinical phenomena. Simulations of the correlation between liver cells, HBV DNA, cytotoxic T lymphocytes and ALT are also given.

Hyperpolarized metabolites offer a tremendous sensitivity advantage (>10(4) fold) when measuring flux and enzyme activity in living tissues by magnetic resonance methods. These sensitivity gains can also be applied to mechanistic studies that impose time and metabolite concentration limitations. Here we explore the use of hyperpolarization by dissolution dynamic nuclear polarization (DNP) in mechanistic studies of alanine transaminase (ALT), a well-established biomarker of liver disease and cancer that converts pyruvate to alanine using glutamate as a nitrogen donor. A specific deuterated, (13)C-enriched analog of pyruvic acid, (13)C3D(3)-pyruvic acid, is demonstrated to have advantages in terms of detection by both direct (13)C observation and indirect observation through methyl protons introduced by ALT-catalyzed H-D exchange. Exchange on injecting hyperpolarized (13)C3D(3)-pyruvate into ALT dissolved in buffered (1)H(2)O, combined with an experimental approach to measure proton incorporation, provided information on mechanistic details of transaminase action on a 1.5s timescale. ALT introduced, on average, 0.8 new protons into the methyl group of the alanine produced, indicating the presence of an off-pathway enamine intermediate. The opportunities for exploiting mechanism-dependent molecular signatures as well as indirect detection of hyperpolarized (13)C3-pyruvate and products in imaging applications are discussed., (Copyright © 2012 Elsevier Inc. All rights reserved.)

We isolated a novel pyridoxal-5-phosphate-dependent l-cystine lyase from the dandelion Taraxacum brevicorniculatum. Real time qPCR analysis showed that C-S lyase from Taraxacum brevicorniculatum (TbCSL) mRNA is expressed in all plant tissues, although at relatively low levels in the latex and pedicel. The 1251 bp TbCSL cDNA encodes a protein with a calculated molecular mass of 46,127 kDa. It is homologous to tyrosine and alanine aminotransferases (AlaATs) as well as to an Arabidopsis thaliana carbon-sulfur lyase (C-S lyase) (SUR1), which has a role in glucosinolate metabolism. TbCSL displayed in vitrol-cystine lyase and AlaAT activities of 4 and 19nkatmg(-1) protein, respectively. However, we detected no in vitro tyrosine aminotransferase (TyrAT) activity and RNAi knockdown of the enzyme had no effect on phenotype, showing that TbCSL substrates might be channeled into redundant pathways. TbCSL is in vivo localized in the cytosol and functions as a C-S lyase or an aminotransferase in planta, but the purified enzyme converts at least two substrates specifically, and can thus be utilized for further in vitro applications., (Copyright © 2012 Elsevier GmbH. All rights reserved.)

Alanine aminotransferase (AlaAT) has been studied in a variety of organisms due to the involvement of this enzyme in mammalian processes such as non-alcoholic hepatocellular damage, and in plant processes such as C4 photosynthesis, post-hypoxic stress response and nitrogen use efficiency. To date, very few studies have made direct comparisons of AlaAT enzymes and fewer still have made direct comparisons of this enzyme across a broad spectrum of organisms. In this study we present a direct kinetic comparison of glutamate:pyruvate aminotransferase (GPAT) activity for seven AlaATs and two glutamate:glyoxylate aminotransferases (GGAT), measuring the K(M) values for the enzymes analyzed. We also demonstrate that recombinant expression of AlaAT enzymes in Eschericia coli results in differences in bacterial growth inhibition, supporting previous reports of AlaAT possessing bactericidal properties, attributed to lipopolysaccharide endotoxin recognition and binding. A probable lipopolysaccharide binding region within the AlaAT enzymes, homologous to a region of a lipopolysaccharide binding protein (LBP) in humans, was also identified in this study. The AlaAT enzyme differences identified here indicate that AlaAT homologues have differentiated significantly and the roles these homologues play in vivo may also have diverged significantly. Specifically, the differing kinetics of AlaAT enzymes and how this may alter the nitrogen use efficiency in plants is discussed.

In this paper we describe the expression, purification, kinetics and biophysical characterization of alanine aminotransferase (AlaAT) from the barley plant (Hordeum vulgare). This dimeric PLP-dependent enzyme is a pivotal element of several key metabolic pathways from nitrogen assimilation to carbon metabolism, and its introduction into transgenic plants results in increased yield. The enzyme exhibits a bi-bi ping-pong reaction mechanism with a K(m) for alanine, 2-oxoglutarate, glutamate and pyruvate of 3.8, 0.3, 0.8 and 0.2 mM, respectively. Barley AlaAT catalyzes the forward (alanine-forming) reaction with a k(cat) of 25.6 s(-1), the reverse (glutamate-forming) reaction with k(cat) of 12.1 s(-1) and an equilibrium constant of ~0.5. The enzyme is also able to utilize aspartate and oxaloacetate with ~10% efficiency as compared to the native substrates, which makes it much more specific than related bacterial/archaeal enzymes (that also have lower K(m) values). We have crystallized barley AlaAT in complex with PLP and l-cycloserine and solved the structure of this complex at 2.7 Å resolution. This is the first example of a plant AlaAT structure, and it reveals a canonical aminotransferase fold similar to structures of the Thermotoga maritima, Pyrococcus furiosus, and human enzymes. This structure bridges our structural understanding of AlaAT mechanism between three kingdoms of life and allows us to shed some light on the specifics of the catalysis performed by these proteins., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Four homologues of alanine aminotransferase have been isolated from shoots of wheat seedlings and purified by saline precipitation, gel filtration, preparative electrophoresis and anion exchange chromatography on Protein-Pak Q 8HR column attached to HPLC. Alanine aminotransferase 1 (AlaAT1) and 2 (AlaAT2) were purified 303- and 452-fold, respectively, whereas l-glutamate: glyoxylate aminotransferase 1 (GGAT1) and 2 (GGAT2) were purified 485- and 440-fold, respectively. Consistent inhibition of AlaAT (EC 2.6.1.2) and GGAT (EC 2.6.1.4) activities by p-hydroxymercuribenzoate points on participation of cysteine residues in the enzyme activity. The molecular weight of AlaAT1 and AlaAT2 was estimated to be 65kDa and both of them are monomers in native state. Nonsignificant differences between K(m) using alanine as substrate and catalytic efficiency (k(cat)/K(m)) for l-alanine in reaction with 2-oxoglutarate indicate comparable kinetic constants for AlaAT1 and AlaAT2. Similar kinetic constants for l-alanine in reaction with 2-oxoglutarate and for l-glutamate in reaction with pyruvate for all four homologues suggest equally efficient reaction in both forward and reverse directions. GGAT1 and GGAT2 were able to catalyze transamination between l-glutamate and glyoxylate, l-alanine and glyoxylate and reverse reactions between glycine and 2-oxoglutarate or pyruvate. Both GGATs also consisted of a single subunit with molecular weight of about 50kDa. The estimated K(m) for GGAT1 (3.22M) and GGAT2 (1.27M) using l-glutamate as substrate was lower in transamination with glyoxylate than with pyruvate (9.52 and 9.09mM, respectively). Moreover, distinctively higher values of catalytic efficiency for l-glutamate in reaction with glyoxylate than for l-glutamate in reaction with pyruvate confirm involvement of these homologues into photorespiratory metabolism., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

As glutamate and ammonia play a pivotal role in nitrogen homeostasis, their production is mediated by various enzymes that are widespread in living organisms. Here, we report on an effective electrophoretic method to monitor these enzymes. The in gel activity visualization is based on the interaction of the products, glutamate and ammonia, with glutamate dehydrogenase (GDH, EC: 1.4.1.2) in the presence of either phenazine methosulfate (PMS) or 2,6-dichloroindophenol (DCIP) and iodonitrotetrazolium (INT). The intensity of the activity bands was dependent on the amount of proteins loaded, the incubation time and the concentration of the respective substrates. The following enzymes were readily identified: glutaminase (EC: 3.5.1.2), alanine transaminase (EC: 2.6.1.2), aspartate transaminase (EC: 2.6.1.1), glycine transaminase (EC: 2.6.1.4), ornithine oxoacid aminotransferase (EC: 2.6.1.13), and carbamoyl phosphate synthase I (EC: 6.3.4.16). The specificity of the activity band was confirmed by high pressure liquid chromatography (HPLC) following incubation of the excised band with the corresponding substrates. These bands are amenable to further molecular characterization by a variety of analytical methods. This electrophoretic technology provides a powerful tool to screen these enzymes that contribute to nitrogen homeostasis in Pseudomonas fluorescens and possibly in other microbial systems., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Background: Gene duplication and the subsequent divergence of paralogous pairs play a central role in the evolution of novel gene functions. S. cerevisiae possesses two paralogous genes (ALT1/ALT2) which presumably encode alanine aminotransferases. It has been previously shown that Alt1 encodes an alanine aminotransferase, involved in alanine metabolism; however the physiological role of Alt2 is not known. Here we investigate whether ALT2 encodes an active alanine aminotransferase., Principal Findings: Our results show that although ALT1 and ALT2 encode 65% identical proteins, only Alt1 displays alanine aminotransferase activity; in contrast ALT2 encodes a catalytically inert protein. ALT1 and ALT2 expression is modulated by Nrg1 and by the intracellular alanine pool. ALT1 is alanine-induced showing a regulatory profile of a gene encoding an enzyme involved in amino acid catabolism, in agreement with the fact that Alt1 is the sole pathway for alanine catabolism present in S. cerevisiae. Conversely, ALT2 expression is alanine-repressed, indicating a role in alanine biosynthesis, although the encoded-protein has no alanine aminotransferase enzymatic activity. In the ancestral-like yeast L. kluyveri, the alanine aminotransferase activity was higher in the presence of alanine than in the presence of ammonium, suggesting that as for ALT1, LkALT1 expression could be alanine-induced. ALT2 retention poses the questions of whether the encoded protein plays a particular function, and if this function was present in the ancestral gene. It could be hypotesized that ALT2 diverged after duplication, through neo-functionalization or that ALT2 function was present in the ancestral gene, with a yet undiscovered function., Conclusions: ALT1 and ALT2 divergence has resulted in delegation of alanine aminotransferase activity to Alt1. These genes display opposed regulatory profiles: ALT1 is alanine-induced, while ALT2 is alanine repressed. Both genes are negatively regulated by the Nrg1 repressor. Presented results indicate that alanine could act as ALT2 Nrg1-co-repressor.

Background: The study aimed to evaluate the diagnostic sensitivity (SE) and specificity (SP) of chronic alcohol misuse diagnosis by comparing traditional biomarkers with ethyl glucuronide (EtG), an ethanol direct metabolite, detected in the keratinic matrix., Methods: Seventy-six subjects tested for chronic alcohol abuse for different purposes were recruited. EtG was detected in hair, whereas the analyses of carbohydrate-deficient transferrin (CDT), alanine transaminase, aspartate transaminase, gamma-glutamyl transferase, mean corpuscular volume, and mean corpuscular hemoglobin were performed in serum samples., Results: Of the 76 patients examined, 26 were judged by the medical doctors as subjects with alcohol abuse problems and, therefore, not eligible for driving license renewal or liver transplant. EtG in hair (SE = 0.68, SP = 1.00) showed the best diagnostic SE and SP compared with the other biomarkers investigated. Among the traditional biomarkers, only CDT proved to be suitable for forensic purposes because of the high diagnostic specificity (SP = 1.00) although it showed poor diagnostic SE (0.27). The percentage of positive samples decreased for all the biomarkers by excluding the subjects with hepatic diseases, except for EtG and CDT, suggesting that these 2 biomarkers could be less affected by false positive results, because of hepatic diseases., Conclusions: This study showed that when EtG in hair and CDT results are combined, diagnostic SE in chronic alcohol abuse diagnosis clearly improved, suggesting that complementary analysis of both these biomarkers provides the best diagnostic tool in suspected cases of chronic excessive alcohol consumption.

Currently, no serum biomarkers, including the biochemical gold standard alanine aminotransferase, can differentiate drug-induced from non-drug-related liver injury, can differentiate liver injury mediated by a specific drug or mechanism, or can accurately predict the progression and outcome of hepatic injury. Efforts have been made by veterinary clinical pathologists, toxicologists, and other scientists to address the gaps in hepatic biomarkers faced during drug development; although there have been no breakthroughs, several novel biomarker candidates have been identified. Efforts to address the gaps in translatable hepatic biomarkers and the challenges and hurdles faced during this process are highlighted in this review., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Alanine aminotransaminase (ALT) has been identified from bacteria to plants to animals including humans. The increase in serum ALT is regarded as an index for clinical diagnosis of liver function in humans. However, ALT elevation is also reported in non-liver injury conditions and in apparently healthy people, suggesting it may play a fundamental role physiologically. Herein we isolated an alt homolog, Amphialt, from Branchiostoma japonicus, an intermediatary species from invertebrates to vertebrates, which encoded a polypeptide of 500 amino acids with more than 62 and 52% sequence identity to vertebrate and invertebrate ALT isoenzymes, respectively. It was constitutively expressed in many tissues including the hepatic caecum, the precursor of liver, and its expression in the caecum was significantly up-regulated by challenge with lipopolysaccharides (LPS). Strikingly, recombinant AmphiALT, with a specific activity of 0.114±0.02U/mg, was capable of specifically binding to the Gram-negative bacteria Escherichia coli and Aeromonas hydrophila and to their conserved molecule LPS, as well as inhibiting the growth of E. coli and causing its lysis. In contrast, AmphiALT did not bind to the Gram-positive bacteria Staphyloccocus aureus and Bacillus subtilis as well as their conserved molecule LTA. In addition, a high homology noted between amphioxus and mammalian ALT sequences suggested a functional conservation of ALT evolutionarily, hinting at the clue that mammalian ALT may also play an antibacterial role similar to that of AmphiALT. Taken together, it is proposed that AmphiALT is an immune-relevant molecule capable of identifying LPS and causing damage to Gram-negative bacteria like E. coli and A. hydrophila. It also bolsters the notion that the hepatic caecum of amphioxus is the precursor of vertebrate liver, acting as a major tissue in acute phase response., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

Alanine aminotransferase (AlaAT) catalyses the reversible conversion of pyruvate and glutamate into alanine and oxoglutarate. In soybean, two subclasses were identified, each represented by two highly similar members. To investigate the role of AlaAT during hypoxic stress in soybean, changes in transcript level of both subclasses were analysed together with the enzyme activity and alanine content of the tissue. Moreover, the dependency of AlaAT activity and gene expression was investigated in relation to the source of nitrogen supplied to the plants. Using semi-quantitative PCR, GmAlaAT genes were determined to be highest expressed in roots and nodules. Under normal growth conditions, enzyme activity of AlaAT was detected in all organs tested, with lowest activity in the roots. Upon waterlogging-induced hypoxia, AlaAT activity increased strongly. Concomitantly, alanine accumulated. During re-oxygenation, AlaAT activity remained high, but the transcript level and the alanine content decreased. Our results show a role for AlaAT in the catabolism of alanine during the initial period of re-oxygenation following hypoxia. GmAlaAT also responded to nitrogen availability in the solution during waterlogging. Ammonium as nitrogen source induced both gene expression and enzyme activity of AlaAT more than when nitrate was supplied in the nutrient solution. The work presented here indicates that AlaAT might not only be important during hypoxia, but also during the recovery phase after waterlogging, when oxygen is available to the tissue again.

The activity of alanine aminotransferase (ALT; E.C. 2.6.1.2) is often changed upon inflammatory responses in animals. Rare earths was shown to provoke various inflammatory responses both in rats and mice; however, the molecular mechanism by which rare earths exert its toxicity has not been completely understood, especially, we know little about the mechanism of the interaction between CeCl(3) and ALT. In this report, we investigated the mechanisms of CeCl(3) on ALT activity in vivo and in vitro. Our results showed that Ce(3+) could significantly activate ALT in vivo and in vitro; the kinetics constant (Km) and Vmax were 0.018 microM and 1,380 unit mg(-1) protein min(-1), respectively, at a low concentration of Ce(3+), and 0.027 microM and 624 unit mg(-1) protein min(-1), respectively, at a high concentration of Ce(3+). By UV absorption and fluorescence spectroscopy assays, the Ce(3+) was determined to be directly bound to ALT; the binding site of Ce(3+) to ALT was 1.72, and the binding constants of the binding site were 4.82 x 10(8) and 9.05 x 10(7) L mol(-1). Based on the analysis of the circular dichroism spectra, it was concluded that the binding of Ce(3+) altered the secondary structure of ALT, suggesting that the observed enhancement of ALT activity was caused by a subtle structural change in the active site through the formation of the complex with Ce(3+).

The erythrocyte is exposed to reactive oxygen species in the circulation and also to those produced by autoxidation of hemoglobin. Consequently, erythrocytes depend on protection by the antioxidant glutathione. Mathematical models based on realistic kinetic data have provided valuable insights into the regulation of biochemical pathways within the erythrocyte but none have satisfactorily accounted for glutathione metabolism. In the current model, rate equations were derived for the enzyme-catalyzed reactions, and for each equation the nonlinear algebraic relationship between the steady-state kinetic parameters and the unitary rate constants was derived. The model also includes the transport processes that supply the amino acid constituents of glutathione and the export of oxidized glutathione. Values of the kinetic parameters for the individual reactions were measured predominately using isolated enzymes under conditions that differed from the intracellular environment. By comparing the experimental and simulated results, the values of the enzyme-kinetic parameters of the model were refined to yield conformity between model simulations and experimental data. Model output accurately represented the steady-state concentrations of metabolites in erythrocytes suspended in plasma and the changing glutathione concentrations in whole and hemolyzed erythrocytes under specific experimental conditions. Analysis indicated that feedback inhibition of gamma-glutamate-cysteine ligase by glutathione had a limited effect on steady-state glutathione concentrations and was not sufficiently potent to return glutathione concentrations to normal levels in erythrocytes exposed to sustained increases in oxidative load.

Kinetic analyses of lactate-dehydrogenase (LD)-coupled alanine transaminase (ALT) reaction processes were investigated for measuring ALT by an integration strategy. For measuring ALT by a kinetic analysis of an LD-coupled ALT reaction curve, candidate reaction curves were calculated via iterative numerical integration of the differential velocity equations to execute a weighted nonlinear-least-square-fitting. To realize the integration strategy, the conventional initial-velocity method was used if the ALT activities were below 25 U/L; otherwise, kinetic analyses of the reaction curves were employed. Of the reaction curves recorded at 10-s intervals, kinetic analyses gave ALT activities resistant to deviations in the LD kinetic parameters. The integration strategy yielded a higher value of the lower limit, but an upper limit of over 100 U/L by simulations and over 75 U/L with purified ALT. Also, its intra-run relative standard deviations were below 9% for 0.50 U/L ALT and below 5% for final 1 to 65 U/L ALT. The integration strategy gave consistent ALT activities in clinical sera. Hence, this new approach for kinetic analyses of ALT reaction processes and the integration strategy were effective to measure ALT.

As part of a study on aminotransferases, genes coding for putative enzymes from Trypanosoma brucei and Leishmania major (alanine aminotransferases: ALATs, Tb927.1.3950 and LmjF12.0630; kynurenine aminotransferase: KAT, Tb10.389.1810; and tyrosine aminotransferase: TAT, LmjF36.2360) were cloned and functionally expressed in Escherichia coli. The putative T. brucei KAT, in fact coded for a glutamine aminotransferase (GlnAT), which exhibited a notably high affinity (in the micromolar range) towards glutamine and cysteine; in addition, like bacterial GlnATs and mammalian KATs, it was able to utilize different 2-oxoacids as amino acceptors. L. major TAT resembled T. cruzi TAT in substrate specificity, although the leishmanial enzyme did not exhibit ALAT activity. On the other hand, T. brucei ALAT, shortened by the first 65 amino acids assigned in the data bases, was functional and actively transaminated the substrate pair l-alanine and 2-oxoglutarate. Moreover in Western blots, the molecular size of the protein detected in crude extracts of T. brucei procyclics was identical to the value of the recombinant enzyme. Like T. brucei and T. cruzi orthologues, L. major ALAT displayed narrow substrate specificity. The leishmanial ALAT, like the T. cruzi enzyme, exhibited a dual subcellular localization, in the cytosol and in the mitochondrion. In line with the findings of comparative proteomic analyses of insect and mammalian stages of T. brucei and Leishmania parasites, our results also showed that T. cruzi ALAT is constitutively expressed, with remarkably higher levels being detected in amastigotes than in epimastigotes. ALATs are expressed in the clinically important stages of TriTryps, probably fulfilling an essential role, which deserves further studies.

Alanine aminotransferase (ALT) is a key enzyme for gluconeogenesis as well as a widely used serum marker for liver injury. We have identified two ALT isoenzymes, ALT1 and ALT2, which are encoded by separate genes. In this study, we described the expression, purification and initial characterization of human ALT1 and ALT2 proteins in High-five insect cells. Human ALT1 and ALT2 were expressed as His-tagged fusion proteins by recombinant baculovirus in insect cells and purified into homogeneity in one step by using immobilized Ni2+-affinity chromatography. Tag-free ALT1 and ALT2 were obtained by cleavage of enterokinase digestion and used for initial characterization of the enzymes. The specific ALT activity of purified fusion or His-tag-removed ALT1 was about 15-fold higher than that of ALT2 and their enzymatic activities decreased quickly at 37 degrees C and -20 degrees C, but were well preserved at -80 degrees C. Nevertheless, the ALT1 and ALT2 activities remained stable in a buffer containing 25% glycerol. The pH profile was similar between hALT1 and hALT2 in that both enzymes remained fully active between pH 6.5 and 8.0. The purified ALT recombinant proteins can not only be used as a reference protein standard for the ALT assay in clinical chemistry, but also will be useful for understanding the biochemical and biological significance of the isoenzymes and for developing ALT isoform-specific assays for clinical or preclinical diagnostic use.

In humans, beta-alanine (BAL) and the neurotransmitter gamma-aminobutyrate (GABA) are transaminated by a single aminotransferase enzyme. Apparently, yeast originally also had a single enzyme, but the corresponding gene was duplicated in the Saccharomyces kluyveri lineage. SkUGA1 encodes a homologue of Saccharomyces cerevisiae GABA aminotransferase, and SkPYD4 encodes an enzyme involved in both BAL and GABA transamination. SkPYD4 and SkUGA1 as well as S. cerevisiae UGA1 and Schizosaccharomyces pombe UGA1 were subcloned, over-expressed and purified. One discontinuous and two continuous coupled assays were used to characterize the substrate specificity and kinetic parameters of the four enzymes. It was found that the cofactor pyridoxal 5'-phosphate is needed for enzymatic activity and alpha-ketoglutarate, and not pyruvate, as the amino group acceptor. SkPyd4p preferentially uses BAL as the amino group donor (V(max)/K(m)=0.78 U x mg(-1) x mm(-1)), but can also use GABA (V(max)/K(m)=0.42 U x mg(-1) x mm(-1)), while SkUga1p only uses GABA (V(max)/K(m)=4.01 U x mg(-1) x mm(-1)). SpUga1p and ScUga1p transaminate only GABA and not BAL. While mammals degrade BAL and GABA with only one enzyme, but in different tissues, S. kluyveri and related yeasts have two different genes/enzymes to apparently 'distinguish' between the two reactions in a single cell. It is likely that upon duplication approximately 200 million years ago, a specialized Uga1p evolved into a 'novel' transaminase enzyme with broader substrate specificity.

Antibody 15A9, raised with 5'-phosphopyridoxyl (PPL)-N(epsilon)-acetyl-L-lysine as hapten, catalyzes the reversible transamination of hydrophobic D-amino acids with pyridoxal 5'-phosphate (PLP). The crystal structures of the complexes of Fab 15A9 with PPL-L-alanine, PPL-D-alanine, and the hapten were determined at 2.3, 2.3, and 2.5A resolution, respectively, and served for modeling the complexes with the corresponding planar imine adducts. The conformation of the PLP-amino acid adduct and its interactions with 15A9 are similar to those occurring in PLP-dependent enzymes, except that the amino acid substrate is only weakly bound, and, due to the immunization and selection strategy, the lysine residue that covalently binds PLP in these enzymes is missing. However, the N-acetyl-L-lysine moiety of the hapten appears to have selected for aromatic residues in hypervariable loop H3 (Trp-H100e and Tyr-H100b), which, together with Lys-H96, create an anion-binding environment in the active site. The structural situation and mutagenesis experiments indicate that two catalytic residues facilitate the transamination reaction of the PLP-D-alanine aldimine. The space vacated by the absent L-lysine side chain of the hapten can be filled, in both PLP-alanine aldimine complexes, by mobile Tyr-H100b. This group can stabilize a hydroxide ion, which, however, abstracts the C alpha proton only from D-alanine. Together with the absence of any residue capable of deprotonating C alpha of L-alanine, Tyr-H100b thus underlies the enantiomeric selectivity of 15A9. The reprotonation of C4' of PLP, the rate-limiting step of 15A9-catalyzed transamination, is most likely performed by a water molecule that, assisted by Lys-H96, produces a hydroxide ion stabilized by the anion-binding environment.

Alanine is the most effective precursor for gluconeogenesis among amino acids, and the initial reaction is catalyzed by alanine aminotransferase (AlaAT). Although the enzyme activity increases during fasting, this effect has not been studied extensively. The present study describes the purification and characterization of an isoform of AlaAT from rat liver under fasting. The molecular mass of the enzyme is 17.7 kD with an isoelectric point of 4.2; glutamine is the N-terminal residue. The enzyme showed narrow substrate specificity for L-alanine with Km values for alanine of 0.51 mM and for 2-oxoglutarate of 0.12 mM. The enzyme is a glycoprotein. Spectroscopic and inhibition studies showed that pyridoxal phosphate (PLP) and free -SH groups are involved in the enzymatic catalysis. PLP activated the enzyme with a Km of 0.057 mM.

Four alanine aminotransferases (AlaATs) are expressed in Medicago truncatula. In adult plants, two genes encoding mitochondrial isoforms m-AlaAT and alanine-glyoxylate aminotransferase (AGT), catalysing, respectively, reversible reactions of alanine/oxoglutarate<==>glutamate/pyruvate and alanine/glyoxylate<==>glycine/pyruvate, were expressed in roots, stems, and leaves. A gene encoding a cytosolic (c-AlaAT) isoform, catalysing the same reaction as m-AlaAT, was expressed specifically in leaves, while a gene encoding an isoform involved in branched chain amino acid metabolism was expressed in stems and roots. In young seedlings, only m-AlaAT and AGT were expressed in embryo axes. In hypoxic embryo axes, the amounts of transcript and putative protein of m-AlaAT (EC 2.6.1.2) increased while those of AGT (EC 2.6.1.44) decreased and in vivo enzyme activities changed as revealed by [(15)N]alanine and [(15)N]glutamate labelling. Under hypoxia, m-AlaAT catalysed only alanine synthesis while glutamate synthesis using alanine as amino donor was inhibited. As a result, alanine accumulated as the major amino acid in hypoxic seedlings instead of asparagine, in agreement with the involvement of the fermentative AlaAT pathway in hypoxia tolerance. Regulation of m-AlaAT at both the transcriptional and post-translational levels allowed for an increase in gene expression and orientation of the activity of the product of its transcription towards alanine synthesis under hypoxia. Labelling experiments showed that glycine synthesis occurred at the expense of either alanine or glutamate as amino donor, indicating that a glutamate-glyoxylate aminotransferase was operating together with AGT in Medicago truncatula seedlings. Both enzymes seemed to be inhibited by hypoxia, resulting in a very low amount of glycine in hypoxic seedlings.

Alanine is the most effective precursor for gluconeogenesis among amino acids and the initial reaction is catalyzed by alanine aminotransferases (AlaATs). It is a less extensively studied enzyme under starvation and known to that the enzyme activity increases in liver under starvation. The present study describes the purification and characterization of two isoforms of alanine aminotransferases from starved male rat liver under starvation. The molecular mass of isoforms was found to be 17.7 and 112.2 kDa with isoelectric points of 4.2 and 5.3 respectively for AlaAT I and AlaAT II. Both the enzymes showed narrow substrate specificity for L-alanine with different Km for alanine and 2-oxoglutarate. Both the enzymes were glycoprotein in nature. Inhibition, modification and spectroscopic studies showed that both PLP and free-SH groups are directly involved in the enzymatic catalysis. PLP activated both the enzymes with a Km 0.057 mM and 0.2 mM for AlaAT I and II respectively.

GABA[arrow beta]AlaAT convertase is an endopeptidase that processes brain-type 4-aminobutyrate aminotransferase (GABA AT; EC 2.6.1.19) to liver-type beta-alanine-oxoglutarate aminotransferase (beta-AlaAT I) in rats. Its molecular mass was 180 kDa as determined by gel filtration. A subunit molecular mass of 97652 Da was measured using MALDI-TOF MS. The N-terminal sequence of the purified GABA[arrow beta]AlaAT convertase was SRVEVSKVLILGSGGLSIGQAGEFDYSGSQAV- and was identical to residues 418-449 of carbamoyl-phosphate synthetase I (CPS I; EC 1.2.1.27) purified from rat liver. The subunit molecular mass and the N-terminal amino acid sequence suggested that GABA[arrow beta]AlaAT convertase was the 418-1305 peptide of CPS I. An expression vector containing the coding region of the 418-1305 peptide of rat CPS I was transfected into NIH3T3 cells and the extract of the cells showed GABA[arrow beta]AlaAT convertase activity.

Purpose: Cold preservation of the liver before transplantation may change uptake and excretory functions of hepatocytes. We hypothesized that an increase in the duration of preservation would result in a progressive decrease in the hepatic uptake and/or biliary excretion of indocyanine green (ICG), which would be attenuated by pharmacologic interventions., Methods: Donor rats (n = 40) were administered saline (control) or single 5 mg/kg doses of methylprednisolone (MP) or its liver-targeted prodrug (DMP) 2 h prior to liver harvest. Following preservation in cold University of Wisconsin solution for 0, 24, 48, or 72 h, livers were reperfused in a single-pass manner for 30 min in the presence of ICG (approximately 4 microg/ml), followed by 60 min of ICG-free perfusion. The inlet, outlet, and bile concentrations of ICG were measured periodically by high performance liquid chromatography (HPLC), and kinetic parameters were estimated., Results: Effects of duration of preservation: In unpreserved livers, a significant portion of ICG dose (16%) was effluxed from the liver during the washout period. Cold preservation for 24-72 h progressively increased (p < 0.05) the efflux of ICG (>2-fold at 72 h). Similarly, average extraction ratio showed a modest (30-40%) decrease with increasing preservation time (p < 0.05). However, biliary excretion of ICG showed the most sensitivity to the preservation time (14 to >800-fold decline). Effects of pretreatment: DMP caused significant (p < 0.05) increases in biliary ICG levels (>12-fold) and bile flow rates (6-15-fold) of preserved livers. Although MP pretreatment significantly (p < 0.05) increased (6-fold) bile flow rates in 48-h preserved livers, its effects on biliary ICG levels were not significant (p > 0.05)., Conclusions: Biliary excretion of ICG is the most sensitive kinetic parameter to prolonged cold ischemia-reperfusion injury in a rat liver perfusion model. The injury may be significantly attenuated by pharmacologic pretreatment of the liver donors.

Herein, we report cloning and subcellular localization of two alanine aminotransferase (ALT) isozymes, cALT and mALT, from liver of gilthead sea bream (Sparus aurata). CHO cells transfected with constructs expressing cALT or mALT as C- or N-terminal fusion with the enhanced green fluorescent protein (EGFP) showed that cALT is cytosolic, whereas mALT localized to mitochondria. Fusion of EGFP to mALT N-terminus or removal of amino acids 1-83 of mALT avoided import into mitochondria, supporting evidence that the mALT N-terminus contains a mitochondrial targeting signal. The amino acid sequence of mALT is the first reported for a mitochondrial ALT in animals.

Cytosolic alanine aminotransferase (c-AAT) was purified up to 203- and 120-fold, from the liver of two freshwater teleosts Clarias batrachus (air-breathing, carnivorous) and Labeo rohita (water-breathing, herbivorous), respectively. The enzyme from both fish showed similar elution profiles on a DEAE-Sephacel ion exchange column. SDS-PAGE of purified enzymes revealed two subunits of 54 and 56 kDa, in both fish. The apparent Km values for l-alanine were 18.5+/-0.48 and 23.55+/-0.60 mM, whereas for 2-oxoglutarate the Km values were observed to be 0.29+/-0.023 and 0.33+/-0.028 mM for the enzyme from C. batrachus and L. rohita, respectively. With l-alanine as substrate, aminooxyacetic acid was found to act as a competitive inhibitor with KI values of 6.4 x 10(-4) and 3.4 x 10(-4) mM with c-AAT of C. batrachus and L. rohita, respectively. However, when 2-oxoglutarate was used as substrate, aminooxyacetic acid showed uncompetitive inhibition with similar KI values for purified c-AAT from both fish. Temperature and pH profiles of the enzyme did not show any marked differences between the two fish examined. These results suggest that liver c-AAT, isolated from these two fish species adapted to different modes of life, remain unaltered structurally. However, at the kinetic level, liver c-AAT from C. batrachus exhibits significantly higher affinity for the substrate l-alanine and decreased affinity for its metabolic inhibitor, in comparison to that of the enzyme purified from L. rohita. Such functional changes seem to be of physiological significance and also provide preliminary evidence for subtle changes in the enzyme as a mark of metabolic adaptation in the fish to different physiological demands.

Alanine aminotransferase (ALT) has been regarded as one of the most sensitive indicators of hepatocellular damage. While ALT is widely used in the practice of medicine, few attempts have been made to develop biosensors applicable to the on-site diagnosis of liver diseases. In the hope of developing an immunosensor for measurement of ALT activity, we have generated monoclonal antibodies to human recombinant ALT and fabricated them for use in a sensor. The ALT immunosensor was composed of the followings: (1) anti-ALT antibody-immobilized outer membrane; (2) pyruvate oxidase-absorbed inner membrane; (3) a self assembled monolayer mediator-coated gold working electrode and an Ag/AgCl reference electrode. The chronoamperometric measurement of the immunosensor was performed with 40 microl of PBS containing substrates and ALT without a washing step in less than 5 min. The dynamic range of ALT immunosensor was presented as five orders of magnitude, ranging between 10 pg/ml and 1 microg/ml. The detection limit and the sensitivity were 10 pg/ml and 26.3 nA/(ng/ml), respectively. In the meantime, the enzyme sensor fabricated without anti-ALT antibody showed much poorer analytical values. The dynamic range, the detection limit, and the sensitivity were 10 ng/ml-100 microg/ml, 10 ng/ml and 11.4 nA/(ng/ml), respectively. The presented results indicated that the immunosensor system provided much better technical performance in all of the aspects evaluated than did the enzyme sensor without the immobilized-antibody.

Rainbow trout (Oncorhynchus mykiss) of two lines selected for low (LR) and high (HR) cortisol stress-responsiveness were subjected to confinement for a period of 336 h. Endocrine (plasma cortisol, hepatic cortisol binding) and metabolic (plasma glucose, lactate, amino acids; hepatic glycogen and alanine aminotransferase levels) indices of stress were measured at intervals in confined and unconfined fish of both lines. During confinement plasma cortisol concentration reached maximum values earlier in HR fish (2h) than in LR fish (6h) returning to control values within 336 h in both lines. Paradoxically, although both HR and LR lines displayed a characteristic metabolic stress response, these changes were more pronounced in LR fish. Plasma glucose and lactate levels increased during confinement in both lines but to a significantly greater extent in LR fish. Confinement significantly elevated plasma amino acids to a greater extent in LR fish than in HR fish. Liver glycogen concentration was depleted most rapidly in LR fish but was significantly higher in confined fish of both lines than controls at the end of the experiment. No significant changes were observed in hepatic alanine aminotransferase activity during confinement. Confined fish of both lines displayed a decrease in hepatic cortisol receptor abundance within 24h and this was more sustained in HR fish. The more pronounced disturbance of a broad range of indicators of stress in confined LR fish, compared to HR fish, throws doubt on the magnitude of the cortisol response being the primary driver of these differences.

In Oreochromis niloticus that had been exposed for 3 months to sublethal concentrations (5 and 15 ppm) of the commercial glyphosate herbicide (C(3)H(8)NO(5)P) Roundup, the organs exhibited varying degrees of histopathological change. In the gills filament cell proliferation, lamellar cell hyperplasia, lamellar fusion, epithelial lifting, and aneurysm were observed. In the liver there were vacuolation of hepatocytes and nuclear pyknosis. Kidney lesions consisted of dilation of Bowman's space and accumulation of hyaline droplets in the tubular epithelial cells. The structural damages could be correlated to the significant increase (p

Herpes simplex virus thymidine kinase (HSV-tk) converts ganciclovir (GCV) into an active compound, which can be incorporated into DNA molecules and terminate DNA synthesis. Gene transfer of HSV-tk followed by GCV administration has been used with success to treat experimental cancer and this strategy has entered into clinical trials. Although it is thought that the cytotoxic effect occurs mainly in tumoral dividing cells, where mitotic activity favors integration of the genotoxic compound into nuclear DNA, there are concerns of potential damage to normal nondividing cells. In the present work we have explored the mechanisms of HSV-tk/GCV toxicity and in particular whether this therapy may cause lesions of mitochondrial DNA (mtDNA) and mitochondrial dysfunction. We found that the administration of GCV to rats injected with adenovirus encoding HSV-tk induced hepatocellular damage characterized by the presence of apoptotic bodies, ballooning of hepatocytes, and severe hepatic steatosis with mitochondria enlargement and cristae dissolution at the ultrastructural level. Remarkably, Southern blot analysis showed substantial reduction in the amount of mtDNA in the liver. Using radiolabeled GCV we could demonstrate incorporation of this compound into both nuclear and mtDNA in HSV-tk-transduced rat hepatocytic cell line MCA-RH7777 and subsequent alteration of mitochondrial function. Our observations confirm that GCV can damage both nuclear and mtDNA in cells transduced with HSV-tk and that this effect could be responsible for severe mitochondrial dysfunction and toxicity in normal nondividing cells. These data are relevant for the design of clinical trials using adenoviral vectors encoding HSV-tk.