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Sclerotinia Stem Rot (SSR) caused by the oxalic acid (OA)-secreting necrotrophic fungal pathogen Sclerotinia sclerotiorum, causes significant yields losses in the crop Brassica sps. Oxalate oxidase (OxO) can metabolize OA to CO2 and H2O2. Degradation of OA during the early phase of fungal-host interaction can interfere with the fungal infection and establishment processes. The present study demonstrates the potential of barley oxalate oxidase (BOxO) gene in conferring stable resistance against stem rot in a productive and highly susceptible Brassica juncea cv Varuna under field conditions. Four stable, independent, single-copy transgenic lines (B16, B17, B18, and B53) exhibited a significant reduction in the rate of lesion expansion i.e. 11-26%, 39-47%, and 24-35% reproducibly over the three-generation i.e. T2, T3, and T4 respectively. The enhanced resistance in the transgenic lines correlated with high OxO activity, accumulation of higher levels of H2O2, and robust activation of defense responsive genes upon infection by S. sclerotiorum.

Background: The aqueous crude extract of Garcinia mangostana fruit pericarp was already proven to contain antiurolithiatic property. Based on this previous study the current study was focused on analysing the anti-urolithiatic property of α- mangostin, a xanthone polyphenol isolated from the fruit pericarp of G. manostana, which has not been tested for its anti-urolithiatic property till now. Objective: The aim of this present study is to evaluate the anti-urolithiatic property of the isolated α- mangostin from G. mangostana fruit pericarp using in silico, in vitro and in vivo analysis. Study Design: Antiurolithiatic activity of α- mangostin through Molecular docking study à In vitro S.S.M model study à Animal studies. Place and Duration: Department of Biotechnology, Sri Venkateswara College of Engineering, Post Bag No.1, Pennalur, Sriperumbudur Tk, Kancheepuram Dt, TN-602117, India. Materials and Methods: In silico Molecular docking of α- mangostin with Kidney stone forming proteins- Xanthine dehydrogenase (Xdh), Oxalate oxidase and Tamm-Horesefall Protein (THP) were performed using AutoDock 4.0 and was visualised in Discovery studio software. In vitro Simultaneous Static flow Model (S.S.M) was performed to investigate its Antiurolithiatic property against Calcium Oxalate (CaOx) and Calcium Phosphate (CaP) crystals. Based on the in silico and in vitro analysis, the study was extrapolated to Ethylene Glycol (EG) induced urolithiasis rat models. The animal study was performed with 36 Albino Wistar rats which were divided into 6 groups. All group except group I received EG (0.75% in drinking water) for the induction of Urolithiasis for 28 days under curative regimen. Group III was administered orally with Cystone (750 mg/kg) from 15th to 28thday. Group IV to VI was administered orally with GMPE (300 mg/kg, 500 mg/kg and 750 mg/kg) from 15thto 28th day. Results: Molecular Docking studies showed an inhibitory interaction of α- mangostin with oxalate oxidase, Xdh and THP with binding affinity of -4.47, -4.00 and -3.41 Kcal/mol respectively. S.S.M showed 54.71% inhibition for CaOx crystals and 62.21% inhibition of CaP crystals. The animal studies showed significant results in reduction of serum calcium (P

Background The evaluation of 24 h urinary oxalate excretion is the gold standard for diagnosing hyperoxaluria in patients with recurrent urolithiasis. However, 24 h urine sample collection is cumbersome. Therefore we aim to see if oxalate to creatinine ratio in random urine sample can be used as an alternative. Materials and methods A cross-sectional study was conducted at Section of Chemical Pathology, Department of Pathology and Laboratory Medicine Aga Khan University Karachi from 1st February to December 31, 2019. A total of 62 adult patients, 18–60 years of age with history of kidney stones presenting to the clinical laboratory for 24 h urine oxalate estimation were invited to participate in the study after informed consent. Clinical details were recorded on a structured questionnaire and patients were guided to submit 24 h urine and a random spot urine sample. Urinary oxalate was measured on Micro lab 300 using a kit based on oxalate oxidase principle by Trinity Biotech plc, Wicklow, Ireland following standard operating procedures. Urinary creatinine was measured on ADVIA 1800 by Siemens, US using kinetic Jaffe reaction according to the manufacturer's instructions. The data was analyzed on SPSS. Results In a period of ten months, a total of 62 subjects were recruited; mean age was 32.4 ± 2.6 years. Males were 49 (79.0%) and females were 13 (20.9%). Correlation was found to be (r = 0.289) by Spearman correlation (p value, Highlights • Oxalate to creatinine ratio is proposed as an alternative to 24 h urine. • Sensitivity & specificity of spot ox:cr ratio was 83.3% and 17.8% respectively. • PPV and NPV of spot ox:cr ratio was 9.8% and 90.9% respectively. • Studies taking diet and molecular testing into consideration are needed.

Measurement of oxalate in the blood is essential for monitoring primary hyperoxaluria patients with progressive renal impairment and on dialysis prior to transplantation. As no external quality assurance scheme is available for this analyte, we conducted a sample exchange scheme between six laboratories specifically involved with the investigation of primary hyperoxaluria to compare results. The methodologies compared were gas chromatography/mass spectrometry (GCMS), ion chromatography with mass spectrometry (ICMS), and enzymatic methods using oxalate oxidase and spectrophotometry. Although individual laboratories performed well in terms of reproducibility and linearity, there was poor agreement (absolute values) between centres as illustrated by a longer-term comparison of patient results from two of the participating laboratories. This situation was only partly related to differences in calibration and mainly reflected the lower recoveries seen with the ultrafiltration of samples. These findings lead us to conclude that longitudinal monitoring of primary hyperoxaluria patients with deteriorating kidney function should be performed by a single consistent laboratory and the methodology used should always be defined. In addition, plasma oxalate concentrations reported in registry studies and those associated with the risk of systemic oxalosis in published studies need to be interpreted in light of the methodology used. A reference method and external quality assurance scheme for plasma oxalate analysis would be beneficial.

Effects of presowing seed treatment of Triticum aestivum L. and Tr. timopheevii Zhuk. wheat with bacteria Bacillussubtilis and B. thuringiensis were studied. Seedling growth, their generation of hydrogen peroxide, and the activities of pathogenesis-related (PR) proteins oxalate oxidase (OxO), peroxidase (PO), proteinase inhibitor (PI), and chitinase upon infection with the causal fungus of bunt Tilletia caries (DC.) Tul. were analyzed. It was found that Bacillus spp. bacteria attenuated the growth suppression of seedlings caused by the bunt infection and alleviated their affection by the pathogen. The found increase in bunt resistance was associated with the boost in the H2O2 level, OxO and PO activities, and transcriptional activities of the chitinase TaChiI gene initiated by Bacillus spp. bacteria. The differences in activation of transcriptional activity of the proteinase inhibitor TaPI gene in soft wheat seedlings under the influence of B. subtilis and B. thuringiensis strains and their mixture were revealed. The results suppose that the wheat resistance to Til. caries may be formed through different paths, which may be related to the nature of the producer organism.

Using real-time PCR analysis, the constitutive expression of PR-protein genes encoding thaumatin-like protein (TLP), peroxidase III (TaPero), chitinase (Chitin), glucanase (Glucan), protease inhibitor (PrInh), oxalate oxidase (OxOxid) and lipid transfer protein (Ltp) was studied in collection varieties of winter wheat. It has been shown that plants of varieties with increased resistance to a complex of leaf pathogens have higher constitutive expression levels of Chitin and PrInh genes, and, to a greater extent, of TLP, TaPero and Glucan genes, compared with non-resistant varieties. It is proposed to use constitutive levels of expression of TLP, TaPero and Glucan genes for the selection of winter wheat varietal samples with increased resistance to the complex of leaf diseases.

PR proteins are the proteins that are structurally diverse but are induced by the invading phytopathogens (bacteria, fungi, viruses, nematodes, etc.), and they have been classified into 17 major families (PR1, PR2, PR3–PR17). Functionally they have been classified into thaumatin/osmotin-like proteins, chitinases, glucanases, defensins, thionins, oxalate oxidase, oxalate oxidase-like proteins/germin-like proteins and lipid transfer proteins and so forth. It has been found that besides providing resistance against invading plant pathogens, they also provide tolerance against various abiotic stresses. Recently, the transgenic overexpression of the PR proteins in crop plants has been found useful in enhancing resistance against plant pathogens. Moreover, many regulatory components of PR proteins have also been reported. Although some PR proteins reduce mycotoxin levels in foodstuffs and act as food preservatives, still PR overexpressing transgenics also have some human health related concerns. Some PR proteins are reported to be allergens/potential allergens to humans. Therefore, the careful evaluation of PR overexpressing transgenic in terms of their toxicity or allergenicity may be evaluated before commercialising them as future genetically modified crops.

Considering the widespread occurrence of oxalate in nature and its broad impact on a host of organisms, it is surprising that so little is known about the turnover of this important acid. In plants, oxalate oxidase is the most well-studied enzyme capable of degrading oxalate, but not all plants possess this activity. Recently, acyl-activating enzyme 3 (AAE3), encoding an oxalyl-CoA synthetase, was identified in Arabidopsis. This enzyme has been proposed to catalyze the first step in an alternative pathway of oxalate degradation. Since this initial discovery, this enzyme and proposed pathway have been found to be important to other plants and yeast as well. In this study, we identify, in Arabidopsis, an oxalyl-CoA decarboxylase (AtOXC) that is capable of catalyzing the second step in this proposed pathway of oxalate catabolism. This enzyme breaks down oxalyl-CoA, the product of AtAAE3, into formyl-CoA and CO2. AtOXC:GFP localization suggested that this enzyme functions within the cytosol of the cell. An Atoxc knock-down mutant showed a reduction in the ability to degrade oxalate into CO2. This reduction in AtOXC activity resulted in an increase in the accumulation of oxalate and the enzyme substrate, oxalyl-CoA. Size exclusion studies suggest that the enzyme functions as a dimer. Computer modeling of the AtOXC enzyme structure identified amino acids of predicted importance in co-factor binding and catalysis. Overall, these results suggest that AtOXC catalyzes the second step in this alternative pathway of oxalate catabolism.

Taro (Colocasia esculenta) starch is known to possess unique physical and functional properties such as low amylose content, A-crystalline form, small granules, higher swelling power, etc. Due to the presence of significant amount of calcium oxalate crystals, the food industry is reluctant to explore this unique and cheap starch source for various food applications. Traditional processes utilizing various physical and chemical methods to remove oxalate content of starch inevitably change its physical and functional properties. However, using oxalate oxidase can effectively remove oxalates without altering the unique properties of starch. Hence, an attempt was made to optimize oxalate oxidase assisted starch extraction process from taro flour using response surface methodology. A central composite design comprising 20 experimental trials with 10 cube points augmented with six axial points and four replicates at the center point was applied. A mathematical model was developed to show the effect of taro flour concentration, enzyme load and incubation time on the oxalate removal. Validity of the model was experimentally verified and found that 98.3% of total oxalates can be removed under optimal conditions. This is the first report of optimization of the production of starch from taro flour using microbial oxalate oxidase.

Jasmonic acid (JA) is an important plant hormone associated with plant–pathogen defense. To study the role of JA in plant–fungal interactions, we applied a JA biosynthesis inhibitor, sodium diethyldithiocarbamate (DIECA), on wheat leaves. Our results showed that application of 10 mM DIECA 0–2 days before inoculation effectively induced resistance to powdery mildew (Bgt) in wheat. Transcriptome analysis identified 364 up‐regulated and 68 down‐regulated differentially expressed genes (DEGs) in DIECA‐treated leaves compared with water‐treated leaves. Gene ontology (GO) enrichment analysis of the DEGs revealed important GO terms and pathways, in particular, response to growth hormones, activity of glutathione metabolism (e.g., glutathione transferase activity), oxalate oxidase, and chitinase activity. Gene annotaion revealed that some pathogenesis‐related (PR) genes, such as PR1.1, PR1, PR10, PR4a, Chitinase 8, beta‐1,3‐glucanase, RPM1, RGA2, and HSP70, were induced by DIECA treatment. DIECA reduced JA and auxin (IAA) levels, while increased brassinosteroid, glutathione, and ROS lesions in wheat leaves, which corroborated with the transcriptional changes. Our results suggest that DIECA can be applied to increase plant immunity and reduce the severity of Bgt disease in wheat fields.

We investigated the effect of presowing treatment of seeds with salicylic (SA) and jasmonic (JA) acids on the growth of wheat Triticum aestivum L. seedlings, generation of hydrogen peroxide (Н2О2) therein, and transcriptional activity of the genes encoding defense proteins—oxalate oxidase (OxO), peroxidase (PO), and proteinase inhibitor (PI)—upon their inoculation with stinking smut pathogen Tilletia caries (DC.) Tull. SA and JA were found to reduce adverse effect of T. caries on growth of seedlings and the extent of their infection by the pathogen. Improvement of plant resistance to T. caries depended on a stimulatory effect of SA and JA on the formation of Н2О2 in plant tissues and changes in activity of ОхО, PO, and catalase. SA was shown to elevate transcriptional activity of the genes of oxalate oxidase and peroxidase. We detected a considerable stimulatory effect of JA on transcriptional activity of the gene encoding proteinase inhibitor. Revealed differences in the activation of defense proteins pointed to differing mechanisms of SA and JA action on protective potential of wheat plants infected with T. caries.

Enzyme therapeutics have great potential for the treatment of systemic disorders such as urolithiasis and nephrocalcinosis, which are caused by the excessive accumulation of oxalate. However, exogenous enzymes have short half-lives in vivo and elicit high immunogenicity, which largely limit the therapeutic outcomes. Herein, we report a delivery strategy whereby therapeutic enzymes are encapsulated within a thin zwitterionic polymer shell to form enzyme nanocapsules. The strategy is exemplified by the encapsulation of oxalate oxidase (OxO) for the treatment of hyperoxaluria, because as-synthesized OxO nanocapsules have a prolonged blood circulation half-life and elicit reduced immunogenicity. Our design of enzyme nanocapsules that enable the systemic delivery of therapeutic enzymes can be extended to various biomedical applications.

BACKGROUND: A state of oxalate homeostasis is maintained in patients with healthy kidney function. However, as GFR declines, plasma oxalate (P(ox)) concentrations start to rise. Several groups of researchers have described augmentation of oxalate secretion in the colon in models of CKD, but the oxalate transporters remain unidentified. The oxalate transporter Slc26a6 is a candidate for contributing to the extrarenal clearance of oxalate via the gut in CKD. METHODS: Feeding a diet high in soluble oxalate or weekly injections of aristolochic acid induced CKD in age- and sex-matched wild-type and Slc26a6(−/−) mice. qPCR, immunohistochemistry, and western blot analysis assessed intestinal Slc26a6 expression. An oxalate oxidase assay measured fecal and P(ox) concentrations. RESULTS: Fecal oxalate excretion was enhanced in wild-type mice with CKD. This increase was abrogated in Slc26a6(−/−) mice associated with a significant elevation in plasma oxalate concentration. Slc26a6 mRNA and protein expression were greatly increased in the intestine of mice with CKD. Raising P(ox) without inducing kidney injury did not alter intestinal Slc26a6 expression, suggesting that changes associated with CKD regulate transporter expression rather than elevations in P(ox). CONCLUSIONS: Slc26a6-mediated enteric oxalate secretion is critical in decreasing the body burden of oxalate in murine CKD models. Future studies are needed to address whether similar mechanisms contribute to intestinal oxalate elimination in humans to enhance extrarenal oxalate clearance.

Oxalate oxidase enzyme in monocotyledonous plants, act as a scavenger to breakdown oxalic acid into carbon dioxide and hydrogen peroxide. They perform several important functions in early plant defence responses, including induction of PR protein synthesis and systemic resistance. In the present study oxalic acid, the virulence factor of fungi, was applied to monocotyledonous plants and it was observed that it activates the innate host immune system, along with secretion of oxalate oxidase. The enzymatic activities of other host defence related enzymes like catalase, superoxide dismutase, ascorbic acid oxidase, phenolic content, phenylalanine ammonia lyase were compared between the control and oxalic acid treated (2mM) plants.

Clarireediasp. (formerly calledSclerotinia homoeocarpa), the fungal pathogen that causes dollar spot of turfgrasses, produces oxalic acid but the role of this toxin inClarireediasp. pathogenesis is unknown. In the current study, whole plant inoculation assays were used to evaluate pathogenesis ofClarireediasp. in various model hosts and investigate the role of oxalic acid in dollar spot disease. These assays revealed that both host endogenous oxalate content and pathogen-produced oxalic acid influence the timing and magnitude of symptom development. In time-course expression analysis, oxalate oxidase and related defense-associated germin-like protein genes in creeping bentgrass showed strong up-regulation starting at 48-72 hpi, indicating that germin-like protein genes are most likely involved in defense following initial contact with the pathogen and demonstrating the importance of oxalic acid inClarireediasp. pathogenesis. Overall, the results of these studies suggest that oxalic acid and host endogenous oxalate content are important for pathogenesis byClarireediasp. and may be associated with the transition from biotrophy to necrotrophy during host infection.

INTRODUCTION AND OBJECTIVES:Urinary oxalate, an integral part of the 24-hour urine stone profile, is used to calculate mineral supersaturations and estimate kidney stone risk. The goal of our labor...

In order to define the role of oxalic acid (OA) in the invasion of Botrytis cinerea in tomato plants, the OA induction of resistance related to oxalate oxidase (O×O) and germin was examined. In greenhouse experiments, OA at 3 mmol/L significantly induced resistance in tomato plants against B. cinerea strains B05.10 and T4, reducing lesion size of 37.55% and 24.91% by compared with distilled water control, respectively, while 20 mmol/L OA increasing by 36.14% and 41.48%. OA contents were 98 and 46 µg/mL when tomato plants were infected by B. cinerea strains B05.10 and T4, respectively. To define the molecular-genetic mechanisms, we compared the gene expression under four different conditions: 3 mmol/L OA-treated plants, 20 mmol/L OA-treated plants, B. cinerea strain B05.10-infected plants (B05.10 Inf plants) and B. cinerea strain T4-infected plants (T4 Inf plants). In 3 mmol/L OA-treated plants, the expressions of O×O and Germin peaked at 48 h after spraying, with approximate threefold and 18-fold increase compared with the control expression, respectively. In T4 Inf plants, the expression (mRNA accumulation) of O×O and Germin reached the highest levels at 24 h after inoculation, with 3- and 13-times that immediately after inoculation, respectively. In total, these findings suggest that elevated levels of OA correlated with increased fungal invasion and lower OA induced resistance in tomato plants by increasing expressions of O×O and Germin.

Kochia sieversiana (Pall.) C.A. Mey. is a forage plant that can grow in extremely alkalinized grasslands at pH 10 or higher. Accumulation of a large amount of oxalic acid (OxA) is a primary characteristic of K. sieversiana. In our study, seedlings of K. sieversiana were exposed to the following conditions: non-stress, salinity (200 mM, a molar ratio of NaCl and Na2SO4 1:1), and alkali stress (200 mM, a molar ratio of NaHCO3 and Na2CO3 1:1). Growth, water content, content of organic acids (including OxA), Na+, and K+, and activities of some OxA metabolism-related enzymes were determined. Results show that glycolate oxidase was the key enzyme for OxA synthesis; however, the carboxylation of phosphoenolpyruvate (PEP) by PEP carboxylase (PEPC) probably played a minor role in the OxA-synthetic pathway. The pathway of L-ascorbic acid catabolism was not the main source of OxA accumulation, and the activity of oxalate oxidase (OxO) involved in OxA decomposition was not a limiting factor for inner OxA accumulation. Taken together, accumulation of a large amount of OxA are not related to the degradation and secretion function of OxO but largely depend upon its synthetic function.

We describe an enzymic colourimetric method for determination of oxalate level in urine using arylamine glass-bound sorghum leaf oxalate oxidase and horseradish peroxidase. The method is based on quantification of H2O2 generated from oxidation of urinary oxalate by immobilized oxalate oxidase, by a colour reaction consisting of 4-aminophnazone, phenol and immobilized peroxidase as chromogen. Minimum detection limit of the method was 0.05 mmol/l. Analytical recovery of added oxalate in urine was 96.8± 3.0% (mean ±S.D.). Within and between day coefficient of variation (CV) for urinary oxalate in urine were < 3.5% and

Oxalate oxidase (EC 1.2.3.4) catalyzes the oxidative cleavage of oxalate to carbon dioxide with the reduction of molecular oxygen to hydrogen peroxide. Oxalate oxidase found its application in clinical assay for oxalate in blood and urine. This study describes the purification and biochemical characterization of an oxalate oxidase produced from an endophytic bacterium, Ochrobactrum intermedium CL6. The cell-free fermentation broth was subjected to two-step enzyme purification, which resulted in a 58.74-fold purification with 83% recovery. Specific activity of the final purified enzyme was 26.78 U mg(-1) protein. The enzyme displayed an optimum pH and temperature of 3.8 and 80°C, respectively, and high stability at 4-80°C for 6 h. The enzymatic activity was not influenced by metal ions and chemical agents (K(+), Na(+), Zn(2+), Fe(3+), Mn(2+), Mg(2+), glucose, urea, lactate) commonly found in serum and urine, with Cu(2+) being the exception. The enzyme appears to be a metalloprotein stimulated by Ca(2+) and Fe(2+). Its Km and Kcat for oxalate were found to be 0.45 mM and 85 s(-1), respectively. This enzyme is the only known oxalate oxidase which did not show substrate inhibition up to a substrate concentration of 50 mM. Thermostability, kinetic properties, and the absence of substrate inhibition make this enzyme an ideal candidate for clinical applications.

Oxalic acid, the simplest of all dicarboxylic acids, is widely found in all plant species (Franceschi and Nakata, 2005). Two pathways exist for oxalate degradation in plants: degradation via oxalate oxidase and ATP- and CoA-dependent decarboxylation of oxalate through a poorly studied series of enzymatic reactions (Giovanelli and Tobin, 1961). Oxalyl-CoA synthetase, the enzyme that initiates the second degradation pathway was recently identified in Arabidopsis thaliana as a protein encoded by ACYL-ACTIVATING ENZYME3 (AAE3).

The response of Triticum aestivum L. to infection by Septoria nodorum Berk, a pathogen causing speckled leaf blotch, was studied. The effect of salicylic acid (SA) and jasmonic acid (JA) signal molecules, as well as chitooligosaccharides (COSs) with different acetylation degrees (ADs), on the accumulation of hydrogen peroxide (Н2О2) in wheat leaves and the pathogenesis-related (PR) proteins of oxalate oxidase (AJ556991.1), peroxidase (TC 151917), and proteinase inhibitor (EU293132.1) was investigated. Treatment with the signal molecules inhibited S. nodorum growth and stimulated Н2О2 accumulation, as well as PR gene expression. SA and COS with 65% AD are found to be more efficient in Н2О2 induction and elevation of the transcriptional level of the oxalate oxidase and peroxidase genes. At the same time, JA and COS with 30% AD stimulated transcription of the proteinase inhibitor gene. The results suggest the existence of differential means of defense response induction by signal molecules with more prospects for the regulation of plant immunity.

Calcium oxalate crystals are widespread among animals and plants. In land plants, crystals often reach high amounts, up to 80% of dry biomass. They are formed within specific cells, and their accumulation constitutes a normal activity rather than a pathological symptom, as occurs in animals. Despite their ubiquity, our knowledge on the formation and the possible role(s) of these crystals remains limited. We show that the mesophyll crystals of pigweed (Amaranthus hybridus) exhibit diurnal volume changes with a gradual decrease during daytime and a total recovery during the night. Moreover, stable carbon isotope composition indicated that crystals are of nonatmospheric origin. Stomatal closure (under drought conditions or exogenous application of abscisic acid) was accompanied by crystal decomposition and by increased activity of oxalate oxidase that converts oxalate into CO2 Similar results were also observed under drought stress in Dianthus chinensis, Pelargonium peltatum, and Portulacaria afra Moreover, in A. hybridus, despite closed stomata, the leaf metabolic profiles combined with chlorophyll fluorescence measurements indicated active photosynthetic metabolism. In combination, calcium oxalate crystals in leaves can act as a biochemical reservoir that collects nonatmospheric carbon, mainly during the night. During the day, crystal degradation provides subsidiary carbon for photosynthetic assimilation, especially under drought conditions. This new photosynthetic path, with the suggested name "alarm photosynthesis," seems to provide a number of adaptive advantages, such as water economy, limitation of carbon losses to the atmosphere, and a lower risk of photoinhibition, roles that justify its vast presence in plants.

Isothermal titration calorimetry (ITC) may be used to determine the kinetic parameters of enzyme-catalyzed reactions when neither products nor reactants are spectrophotometrically visible and when the reaction products are unknown. We report here the use of the multiple injection method of ITC to characterize the catalytic properties of oxalate oxidase (OxOx) from Ceriporiopsis subvermispora (CsOxOx), a manganese dependent enzyme that catalyzes the oxygen-dependent oxidation of oxalate to carbon dioxide in a reaction coupled with the formation of hydrogen peroxide. CsOxOx is the first bicupin enzyme identified that catalyzes this reaction. The multiple injection ITC method of measuring OxOx activity involves continuous, real-time detection of the amount of heat generated (dQ) during catalysis, which is equal to the number of moles of product produced times the enthalpy of the reaction (ΔHapp). Steady-state kinetic constants using oxalate as the substrate determined by multiple injection ITC are comparable to those obtained by a continuous spectrophotometric assay in which H2O2 production is coupled to the horseradish peroxidase-catalyzed oxidation of 2,2′-azinobis-(3-ethylbenzthiazoline-6-sulfonic acid) and by membrane inlet mass spectrometry. Additionally, we used multiple injection ITC to identify mesoxalate as a substrate for the CsOxOx-catalyzed reaction, with a kinetic parameters comparable to that of oxalate, and to identify a number of small molecule carboxylic acid compounds that also serve as substrates for the enzyme.

Calcium oxalate (CaOx) crystals are widespread among plant species. Their functions are not yet completely understood; however, they can provide tolerance against multiple environmental stress factors. Recent evidence suggested that CaOx crystals function as carbon reservoirs since its decomposition provides CO2 that may be used as carbon source for photosynthesis. This might be advantageous in plants with reduced mesophyll conductance, such as the Antarctic plant Colobanthus quitensis, which have shown CO2 diffusion limitations. In this study, we evaluate the effect of two CO2 concentrations in the CaOx crystals decomposition and chlorophyll fluorescence of C. quitensis. Plants were exposed to airflows with 400 ppm and 11.5 ppm CO2 and the number and relative size of crystals, electron transport rate (ETR), and oxalate oxidase (OxO) activity were monitored along time (10 h). Here we showed that leaf crystal area decreases over time in plants with 11.5 ppm CO2, which was accompanied by increased OxO activity and only a slight decrease in the ETR. These results suggested a relation between CO2 limiting conditions and the CaOx crystals decomposition in C. quitensis. Hence, crystal decomposition could be a complementary endogenous mechanism for CO2 supply in plants facing the Antarctic stressful habitat.

Four oxalate oxidase (OxO) positive fungal strains were isolated from rotting taro corms. One isolate showing highest extra cellular OxO titre was selected and was identified based on partial sequencing of 18S rRNA. The selected strain was found to be Fusarium oxysporum f. sp. cumini. Oxalate oxidase (EC 1.2.3.4) titre was increased by one factor at a time approach in shake flasks. The enzyme was then purified by isopropanol precipitation followed by chromatography using ENrich SEC650 FPLC column. OxO was found to be a heterodimer having two subunits of mass 116 and 105 kDa. Optimum pH and temperature were found to be 3.8 and 80 °C respectively. OxO exhibited stability for 4 h at temperature range of 4–95 °C and pH between 2.2 and 10.0. OxO was inactive until 30 °C and more than 90% of its peak activity was observed at temperature above 80 °C, suggesting that the enzyme is thermophilic. OxO appears to be a metalloprotein inhibited by Cu2+, Fe2+ and EDTA and enhanced in the presence of Mn2+ and biotin. OxO also exhibited broad substrate specificity. This enzyme was found to decompose insoluble calcium oxalate crystals. This is the first report of OxO decomposing calcium oxalate crystals.

The germin-like protein (GLP) purified from Thevetia peruviana, Peruvianin-I, is the only one described as having proteolytic activity. Therefore, the goal of this study was to investigate the structural features responsible for its enzymatic activity. Although the amino acid sequence of Peruvianin-I showed high identity with other GLPs, it exhibited punctual mutations, which were responsible for the absence of oxalate oxidase activity. The phylogenetic analysis showed that Peruvianin-I does not belong to any classification of GLP subfamilies. Moreover, Peruvianin-I contains a catalytic triad found in all plant cysteine peptidases. Molecular docking simulations confirmed the role of the catalytic triad in its proteolytic activity. Synchrotron radiation circular dichroism assays confirmed that Peruvianin-I was stable at pH ranging from 5.0 to 8.0 and that it presented significant structural changes only above 60 °C. The addition of iodoacetamide caused changes in its native conformation, but only a slight effect was observed after adding a reducing agent. This study reports an unusual protein with germin-like structure, lacking typical oxalate oxidase activity. Instead, the proteolytic activity observed suggests that the protein is a cysteine peptidase. These structural peculiarities make Peruvianin‑I an interesting model for further understanding of the action of laticifer fluids in plant defense.

Oxalic acid is a naturally occurring metabolite in plants and a common constituent of all plant-derived human diets. Oxalic acid has diverse unrelated roles in plant metabolism, including pH regulation in association with nitrogen metabolism, metal ion homeostasis and calcium storage. In plants, oxalic acid is also a pathogenesis factor and is secreted by various fungi during host infection. Unlike those of plants, fungi and bacteria, the human genome does not contain any oxalate-degrading genes, and therefore, the consumption of large amounts of plant-derived oxalate is considered detrimental to human health. In this review, we discuss recent biotechnological approaches that have been used to reduce the oxalate content of plant tissues.

In this study, we performed the first comparative proteomic analysis of wheat flag leaves and developing grains in response to drought stress. Drought stress caused a significant decrease in several important physiological and biochemical parameters and grain yield traits, particularly those related to photosynthesis and starch biosynthesis. In contrast, some key indicators related to drought stress were significantly increased, including malondialdehyde, soluble sugar, proline, glycine betaine, abscisic acid content, and peroxidase activity. Two-dimensional difference gel electrophoresis (2D-DIGE) identified 87 and 132 differentially accumulated protein (DAP) spots representing 66 and 105 unique proteins following exposure to drought stress in flag leaves and developing grains, respectively. The proteomes of the two organs varied markedly, and most DAPS were related to the oxidative stress response, photosynthesis and energy metabolism, and starch biosynthesis. In particular, DAPs in flag leaves mainly participated in photosynthesis while those in developing grains were primarily involved in carbon metabolism and the drought stress response. Western blotting and quantitative real-time polymerase chain reaction (qRT-PCR) further validated some key DAPs such as rubisco large subunit (RBSCL), ADP glucose pyrophosphorylase (AGPase), chaperonin 60 subunit alpha (CPN-60 alpha) and oxalate oxidase 2 (OxO 2). The potential functions of the identified DAPs revealed that a complex network synergistically regulates drought resistance during grain development. Our results from proteome perspective provide new insight into the molecular regulatory mechanisms used by different wheat organs to respond to drought stress.

The latex from Thevetia peruviana is rich in plant defense proteins, including a 120 kDa cysteine peptidase with structural characteristics similar to germin-like proteins. More than 20,000 plant species produce latex, including Apocynaceae, Sapotaceae, Papaveraceae and Euphorbiaceae. To better understand the physiological role played by latex fluids, a proteomic analysis of Thevetia peruviana (Pers.) Schum latex was performed using two-dimensional gel electrophoresis and mass spectrometry. A total of 33 proteins (86 %) were identified, including storage proteins, a peptidase inhibitor, cysteine peptidases, peroxidases and osmotins. An unusual cysteine peptidase, termed peruvianin-I, was purified from the latex by a single chromatographic step involving gel filtration. The enzyme (glycoprotein) was inhibited by E-64 and iodoacetamide and exhibited high specific activity towards azocasein (K m 17.6 µM), with an optimal pH and temperature of 5.0–6.0 and 25–37 °C, respectively. Gel filtration chromatography, two-dimensional gel electrophoresis, and mass spectrometry revealed that peruvianin-I possesses 120 kDa, pI 4.0, and six subunits (20 kDa). A unique N-terminal amino acid sequence was obtained to oligomer and monomers of peruvianin-I (1ADPGPLQDFCLADLNSPLFINGYPCRNPALAISDDF36). High-resolution images from atomic force microscopy showed the homohexameric structure of peruvianin-I may be organized as a trimer of dimers that form a central channel similar to germin-like proteins. Peruvianin-I exhibited no oxalate oxidase and superoxide dismutase activity or antifungal effects. Peruvianin-I represents the first germin-like protein (GLP) with cysteine peptidase activity, an activity unknown in the GLP family so far.

Renal urolithiasis is a pathological condition common to a multitude of genetic, physiological and nutritional disorders, ranging from general hyperoxaluria to obesity. The concept of quickly dissolving renal uroliths via chemolysis, especially calcium-oxalate kidney stones, has long been a clinical goal, but yet to be achieved. Over the past 25 years, there has been a serious effort to examine the prospects of using plant and microbial oxalate-degrading enzymes known to catabolize oxalic acid and oxalate salts. While evidence is emerging that bacterial probiotics can reduce recurrent calcium-oxalate kidney stone disease by lowering systemic hyperoxaluria, the possible use of free oxalate-degrading enzyme therapy remains a challenge with several hurdles to overcome before reaching clinical practice.

Oxalic acid (OA) is considered as an important pathogenetic factor of some destructive diseases caused by some fungal pathogens such as Sclerotinia sclerotiorum. Oxalate degradation is important for plant health, and plants that contain oxalate oxidase (OXO) enzymes could breakdown oxalate into CO 2 and H 2 O 2 , which subsequently evokes defense responses. However, some species, such as Arabidopsis thaliana, have no oxalate oxidase activity identified to date. The present study aims to develop transgenic Arabidopsis expressing a wheat oxalate oxidase, to test for the response to OA exposure and fungal infection by S. sclerotiorum. The results showed that the transgenic Arabidopsis lines that expressed the wheat OXO exhibited enhanced resistance to OA exposure and S. sclerotiorum infection in the tolerance assays. In the same manner, it could convert OA to CO 2 and H 2 O 2 to a higher extent than the wild-type. Intensive osmotic adjustments were also detected in the transgenic Arabidopsis lines. The higher level of produced H 2 O 2 subsequently induced an elevated activity of antioxidant enzymes including superoxide dismutase (SOD) and peroxidase (POD) in the transgenic Arabidopsis plants. The present study indicated that the expression of a gene encoding wheat OXO could induce intensive osmotic adjustments and hydrogen peroxide related defense response, and subsequently increased tolerance to S. sclerotiorum in transgenic A. thaliana.

The biochemical and enzymatic properties of four highly similar rice oxalate oxidase proteins (OsOxO1-4) were compared after their purification from the leaves of transgenic plants each overexpressing the respective OsOxO1-4 genes. Although alignment of their amino acid sequences has revealed divergence mainly in the signal peptides and they catalyze the same enzymic (oxalate oxidase) reaction, divergence in apparent molecular mass, Km, optimum pH, stability and responses to inhibitors and activators was uncovered by biochemical characterization of the purified OsOxO1-4 proteins. The apparent molecular mass of oligomer OsOxO1 was found to be similar to that of OsOxO3 but lower than the other two. The molecular mass of the subunit of OsOxO1 was lower than that of OsOxO3. The Km value of OsOxO3 was higher than the other three which had similar Km. OsOxO1 and OsOxO4 possessed peak activity at pH 8.5 which was close to that at the optimum pH 4.0. The activity of OsOxO2 at pH 8.5 was only 65% of that at its optimum pH 3.5, while the activity of OsOxO3 did not vary much at pH 6-9 and was also much lower than that at its optimum pH 3. OsOxO2 and OsOxO3 still maintained all their activities after being heated at 70°C for 1h while OsOxO1 and OsOxO4 lost about 30% of their activities. Pyruvate and oxaloacetic acid inhibited the activity of OsOxO3 more strongly than the other three. Interestingly, glucose 6-phosphate, fructose 6-phosphate and fructose 1,6-biphosphate related to photosynthetic assimilation of triose phosphate greatly increased the activities of OsOxO3 and OsOxO4. In addition to the differences in the biochemical properties of the four OsOxO proteins, an intriguing finding is that the purified OsOxO1-4 exhibited substrate inhibition, which is a typical of the classical Michaelis-Menten enzyme kinetics exhibited by a majority of other enzymes.

Oxalate oxidase (OxOx), a well known enzyme catalyzes the cleavage of oxalate to carbon dioxide with reduction of dioxygen to hydrogen peroxide, however its catalytic process is not well understood. To define the substrate binding site, interaction of Fe(3+) ions with OxOx was systemically investigated using biochemical method, circular dichrosim spectroscopy, microscale thermophoresis, and computer modeling. We demonstrated that Fe(3+) is a non-competitive inhibitor with a milder binding affinity to OxOx, and the secondary structure of the OxOx was slightly altered upon its binding. On the basis of the structural properties of the OxOx and its interaction with Fe(3+) ions, two residue clusters of OxOx were assigned as potential Fe(3+) binding sites, the mechanism of the inhibition of Fe(3+) was delineated. Importantly, the residues that interact with Fe(3+) ions are involved in the substrate orienting based on computer docking. Consequently, the interaction of OxOx with Fe(3+) highlights insight into substrate binding site in OxOx.

Sclerotinia stem rot (SSR) is a severe disease of oilseed rape, which severely impacts the crop productivity worldwide. Sclerotinia sclerotiorum causes SSR, resulting in the secretion of oxalic acid (OA), which can be further degraded to carbon dioxide (CO2) and hydrogen peroxide (H2O2) by oxalate oxidase (OXO). In the present investigation, the barley oxalate oxidase (BOXO, Y14203) gene was introduced into oilseed rape by Agrobacterium-mediated transformation to investigate the mechanism by which OXO promotes resistance to S. sclerotiorum. Compared to the control 72 h post-inoculation, there were c. 15–61% fewer lesions on leaves of the transgenic oilseed rape, which thus exhibited a detectable level of partial resistance in leaf tissue to S. sclerotiorum. Transgenic oilseed rape also showed decreased oxalate and increased hydrogen peroxide levels compared to the control, and the expression of defence response genes involved in the hydrogen peroxide signalling pathway was also induced. Therefore, the improved resistance of oilseed rape could be attributed to the enhanced OA metabolism, production of hydrogen peroxide and the hydrogen peroxide-mediated defence levels during infection.

Background: Traditionally known as Pashanabheda in India, Aerva lanata (L) belonging to the family Amaranthaceae, is widely available in Western ghats of India and used as Antiurolithiatic, astringent, diuretic, antimicrobial, antiinflammatory, hepatoprotective drug by Indian traditional system of medicines. Materials and Method: In the present study this herb is subjected to extraction with hydro alcohol followed by fractionation with different solvents of varying polarities such as dichloromethane, ethyl acetate and n-butanol and screened for Antiurolithiatic activity using ethylene glycol induced male Wistar albino rats. Based on the results, the potent fractions were subjected to isolation of active constituents using column chromatography. Results: The isolated compounds from two fractions n-butanol and ethyl acetate were characterized by modern analytical techniques such as IR, HPTLC, NMR and LCMS as Quercetin and Betulin. Later these two compounds were studied for Antiurolithiatic activity by In silico technique by docking with a protein 2 ETE of Oxalate oxidase from PDB and the results indicated better regio-specificity with the enzyme. Conclusion: The two compounds isolated from potent fractions based on bioactivity guided fractionation were characterized as Quercetin and Betulin by modern analytical techniques. These two compounds were studied by in silico method and these two compounds have produced significant results which substantiate their claim of bioactivity. However in vivo study is needed to confirm the activity.

The synthesis and structure of [MnLCl]0.5H2O (1·0.5H2O, HL = 1-benzyl-4-acetato-1,4,7-triazacyclononane) is reported. Complex 1 exists as a coordination polymer in the solid state, and the MnII center is bonded to three amine nitrogen atoms, one carboxylate oxygen atom, a chlorido ligand, and an adjacent carboxylate group in a chelating fashion to afford a seven-coordinate center. The dissolution of 1 in acetonitrile containing excess oxalate (ox) ions results in a monomeric species. When mixtures of 1 and oxalate ions are exposed to oxygen under ambient conditions, a dark pink EPR-silent species is generated. The pink species is believed to be [MnIII(ox)2]–, which results from the displacement of the ligand L– by an oxalate ion. The decomposition of this species ultimately results in the formation of 1 equiv. of CO2 per oxalate ion consumed, a HCO3– ion, and a MnII species. Further reaction of the resulting MnII species with excess oxalate in the presence of oxygen leads to additional oxalate degradation.

Typha angustifolia L. (Typhaceae) is an emergent aquatic plant, and aerenchyma is formed through cell lysis in its leaves. The developing aerenchyma of T. angustifolia contains many CaOx crystals (raphides). Oxalate oxidase (OXO) (oxalate : oxygen oxidoreductase, EC1.2.3.4) can degrades calcium oxalate to carbon dioxide and hydrogen peroxide (H2O2). High level of H2O2 acts as a key inducer for different types of developmentally and environmentally programmed cell death (PCD) and can promote the formation of aerenchyma. Therefore, the objective of this study was to describe the relationship between aerenchyma formation and the degradation of CaOx crystals. Light and transmission electron microscopy (TEM) results showed that CaOx crystals occurred between PCD-susceptible cells in the early phase of aerenchyma formation, and those cells and CaOx crystals were degraded at aerenchyma maturation. Cytochemical localisation was used to detect H2O2, and H2O2 was found in crystal idioblasts. In addition, the oxalate content, H2O2 content and OXO activity were determined. The results showed that the concentration of oxalate was the highest in the third cavity formation stage and the H2O2 concentration was also highest at this stage. Meanwhile, the activity of OXO was also high in the third cavity formation stage. TpOXO was highly expressed during the CaOx crystal degradation period by quantitative real-time PCR analysis. These results show that the degradation of CaOx crystals is involved in the regulation of the PCD process of aerenchyma. This study will contribute to understanding the changes in CaOx crystals during the formation of aerenchyma in T. angustifolia.

Objective To develop recombinant lactic acid bacteria (LAB) strains that express oxalate-degrading enzymes through biotechnology-based approach for the treatment of hyperoxaluria by oral administration. Material and Methods The coding gene of oxalate decarboxylase (ODC) and oxalate oxidase (OxO) was transformed into Lactococcus lactis MG1363. The oxalate degradation ability in vitro was evaluated in media with high concentration of oxalate. Hyperoxaluria rat models through high oxalate diet were given recombinant LAB through oral administration. Twenty-four-hour urinary oxalate was measured, and kidney stone formation was investigated. Results LAB recombined with the coding gene of ODC could effectively decrease the amount of oxalate in the media and in the urine of rats. Moreover, the formation of calcium oxalate crystals in kidneys was also inhibited. The acid-induced promoter p170 significantly enhanced the reduction of hyperoxaluria. However, recombinant LAB expressing heterologous OxO showed less efficiency in oxalate degradation even in the presence of p170. Conclusion LAB expressing ODC is more efficient in degradation of oxalate in vitro and in vivo than that expressing OxO. This present study provided novel recombinant probiotic strains as a potential treatment tool against oxalosis.

The effect of 1-methylcyclopropene (1-MCP), which inhibits the reception of ethylene, on the following has been studied: hydrogen peroxide generation, oxalate oxidase activity, peroxidase activity, catalase activity, and lignin accumulation in infected leaves of soft spring wheat (Triticum aestivum L.) cultivars that differ in their resistance to the leaf blotch disease, caused by the hemibiotrophic fungus Septoria nodorum Berk. A decrease in the development of leaf blotch in wheat leaves under the influence of 1-MCP was, on one hand, followed by an inhibition of catalase activity; on the other hand, it was accompanied by an increase in oxalate oxidase and peroxidase activity, as well as an accumulation of H2O2 in tissues and lignin in the infected zone. The role of the ethylene reception system in the defense response of plants to infection with a hemibiotrophic pathogen, that causes leaf blotch disease, is discussed.

Membrane inlet mass spectrometry (MIMS) uses a semipermeable membrane as an inlet to a mass spectrometer for the measurement of the concentration of small uncharged molecules in solution. We report the use of MIMS to characterize the catalytic properties of oxalate oxidase (E.C. 1.2.3.4) from Ceriporiopsis subvermispora (CsOxOx). Oxalate oxidase is a manganese dependent enzyme that catalyzes the oxygen-dependent oxidation of oxalate to carbon dioxide in a reaction that is coupled with the formation of hydrogen peroxide. CsOxOx is the first bicupin enzyme identified that catalyzes this reaction. The MIMS method of measuring OxOx activity involves continuous, real-time direct detection of oxygen consumption and carbon dioxide production from the ion currents of their respective mass peaks. 13 C 2 -oxalate was used to allow for accurate detection of 13 CO 2 ( m / z 45) despite the presence of adventitious 12 CO 2 . Steady-state kinetic constants determined by MIMS are comparable to those obtained by a continuous spectrophotometric assay in which H 2 O 2 production is coupled to the horseradish peroxidase catalyzed oxidation of 2,2′-azinobis-(3-ethylbenzthiazoline-6-sulphonic acid). Furthermore, we used MIMS to determine that NO inhibits the activity of the CsOxOx with a K I of 0.58 ± 0.06 μM.

Peroxidase and hydrogen peroxide both play important roles in the final stages of the lignification pathway. Peroxidase, in the presence of H2O2 catalyses the oxidation of monolignols to give lignin. In order to examine this process we looked at lignification in transgenic tobacco plants expressing a barley peroxidase gene, HvPrx8, either alone or in combination with a wheat germin gene, g.f 2.8, which encodes oxalate oxidase, thereby providing a source of H2O2. Elevated activity of the antioxidant ascorbate peroxidase was found in plants expressing oxalate peroxidase and was greatly increased by co-expression with the barley peroxidase, although the latter had no effect when expressed alone. An increase was observed in the oxidation of the lignin monomer, syringaldazine in cell lines over-expressing barley peroxidase, while a decrease was observed in double transformants. Plants over-expressing barley peroxidase have elevated levels of lignin deposition compared to that of wild type tobacco plants. Over-expression of the individual enzymes was also shown to enhance heat-induced programmed cell death (PCD) in cell suspension cultures, an effect which was greatly reduced in the double-expressing lines.

The influence of exogenic hormones (indole-3-acetic acid (IAA), abscisic acid (ABA) and kinetin) on defense reaction of wheat (Triticum aestivum L.) calli to the bunt agent Tilletia caries (D.C.) Tul. & C. Tul. was studied. ABA and kinetin induced the oxalate oxidase activity, increased the Н2О2 level, decreased germination of fungi teliospores and induced on calli the occurrence of dense sites non-infected by pathogen. On the contrary, IAA led to the decrease of oxalate oxidase activity, loosening of calli and increase germination of bunt agent teliospores and growth of fungi mycelium, besides stimulated rhizoids formation of wheat calli. Probably, the accumulation of Н2О2 in wheat calli under the influence of kinetin and ABA connected with activity of oxalate oxidase is one of the factors increasing defense reaction of wheat to bunt agent.

Abscisic acid (ABA), H2O2 and nitric oxide (NO) are important signals in gene expression and physiological responses during plant adaptation to environmental stresses. The essential role of NR-derived NO production in ABA and H2O2 induced antioxidant enzymes were studied using transgenic tobacco plants over-expressing Stylosanthes guianensis 9-cis-epoxycartenoid dioxygenase gene (SgNCED1) for elevated ABA level, or over-expressing wheat oxalate oxidase gene (OxO) for elevated H2O2 level in comparison to the wild type. Compared to the wild type, higher levels of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and nitrate reductase (NR) activities and NO production were observed in all transgenic plants. For investigating the relationship of ABA, H2O2, and NR-produced NO in the induction of antioxidant enzyme activities, an inhibitor of ABA biosynthesis, scavengers of H2O2 and NO, and an inhibitor of NR were used in the experiments. The results indicate that H2O2-induced activities of SOD, CAT, and APX depends on NR-derived NO in OxO transgenic plants, while ABA-induced activities depends on H2O2 and NR-derived NO in SgNCED1 transgenic plants. Compared to unaltered nitrate reductase 2 (NIA2), NIA1 transcript was induced in both types of transgenic plants. It is suggested NR-derived NO is essential for ABA- or H2O2-induced antioxidant enzyme activities.

The total oxalate contents of various vegetables, legume seeds, cereals, fruits and nuts commonly available in Southern China were determined using an improved enzymatic method. Spinach, xeric water spinach (grows on moist soil), amaranth, bamboo shoot, ginger, Chinese wolfberry, rice bean and black glutinous rice contained more than 100mg oxalate/100gFW, but leaf mustard, white radish, broccoli, cauliflower, cabbage, onion, gourd except bitter melon, tomato, pepper, chufa, kelp, mushroom, soybean sprout and cowpea contained less than 10mg oxalate/100gFW. The oxalate contents of star fruit and dragon fruit were 111.4 and 97.1mg/100gFW, respectively, and those of other fruits except strawberry and black plum were less than 20mg/100gFW. Almond, cashew, hazel, pine nut and abalone fruit contained more than 150mg total oxalate/100gFW, and the oxalate levels in Chinese torreya fruit, peanut, pistachio and walnut ranged from 54.1 to 83.1mg/100gFW. Based on the results obtained, water spinach, Chinese wolfberry, black glutinous rice, dragon fruit, rice bean, abalone fruit and Chinese torreya fruit should also be considered as high oxalate-foods. The enzymatic method used in the present study enabled us to perform a large-scale quantitative investigation of oxalate contents of different foods.

Oxalate oxidase has potential to act as an oxygen scavenger in active packaging to increase the shelf-life of food and beverages, while simultaneously producing the protective packaging gas carbon ...

Blood and urine oxalate determinations have been limited to the laboratory setting because of complex sample storage and processing methods as well as the need for color spectrophotometry and ion chromatography. We hypothesized that glucometer test strips, impregnated with glucose oxidase and dyes that measure secondary hydrogen peroxide production, could be infused with oxalate oxidase and produce enhanced color changes in the presence of oxalate. By increasing the amount of sodium oxalate in fresh blood, we found that glucometer-measured oxalate increased on a linear scale. In addition, oxalate levels in synthetic urine could be measured using a visual scale, suggesting that strip dwell time or oxalate/oxalate oxidase concentrations could be manipulated to enhance optimal sensitivity. Although further testing is necessary, this simple, first-generation oxometer may eventually allow point of care testing in the home or office, empowering patients with oxalate-based medical conditions and giving healthcare providers real-time oxalate feedback.

Oxalate oxidase was identified in mycelial extracts of a basidiomycete Abortiporus biennis strain. Intracellular enzyme activity was detected only after prior lowering of the pH value of the fungal cultures by using oxalic or hydrochloric acids. This enzyme was purified using size exclusion chromatography (Sephadex G-25) and ion-exchange chromatography (DEAE-Sepharose). This enzyme exhibited optimum activity at pH 2 when incubated at 40°C, and the optimum temperature was established at 60°C. Among the tested organic acids, this enzyme exhibited specificity only towards oxalic acid. Molecular mass was calculated as 58 kDa. The values of K m for oxalate and V max for the enzyme reaction were 0.015 M and 30 mmol min -1 , respectively.

This study describes the influence of copper nanoparticles (CNPs) on activity and kinetic properties of a Cu2+ requiring sorghum oxalate oxidase (OxO). CNPs were synthesised by citrate-induced reduction of CuCl2 and their size (range 13–58 nm) was determined by transmission electron microscopy. The CNPs were characterised by scanning electron microscopy and X-ray diffraction studies. These CNPs enhanced OxO activity by 30%. Thermal and storage stability were increased, while Km value for oxalate decreased in the presence of CNPs. CNPs protected OxO against chelation by diethyldithiocarbamate, a Cu2+ specific chelator. The analytic use of OxO in the presence of CNP for determination of oxalate in food stuff is demonstrated.