ascorbic-acid and glyoxylic-acid

The reactions that culminate in the synthesis of oxalate in human cells have not yet been clarified. Glycolate and glyoxylate appear to be major precursors. Experimental problems and unresolved issues are highlighted in this review. Assumptions that have been made with out experimental support are identified. The recognition of these assumptions and the testing of their validity should advance our knowledge of the pathways involved, their regulation, and their physiologic significance.

Topics: Ascorbic Acid; Glycolates; Glyoxylates; Humans; Hyperoxaluria; Models, Biological; Oxalates

Tartaric acid has high economic value as an antioxidant and flavorant in food and wine industries. l-Tartaric acid biosynthesis in wine grape (

Topics: Aldo-Keto Reductases; Ascorbic Acid; Catalytic Domain; Glyoxylates; Plant Proteins; Pyruvic Acid; Substrate Specificity; Sugar Acids; Tartrates; Vitis

Methylation of cytosine to 5-methylcytosine (5mC) is a prevalent DNA modification found in many organisms. Sequential oxidation of 5mC by ten-eleven translocation (TET) dioxygenases results in a cascade of additional epigenetic marks and promotes demethylation of DNA in mammals

Topics: 5-Methylcytosine; Algal Proteins; Ascorbic Acid; Biocatalysis; Carbon Dioxide; Chlamydomonas reinhardtii; DNA; DNA Methylation; Glyoxylates; Nucleosides; Photosynthesis

During the developmental processes from dry seeds to seedling establishment, the glyoxylate cycle becomes active in the mobilization of stored oils in the scutellum of barley (Hordeum vulgare L.) seeds, as indicated by the activities of isocitrate lyase and malate synthase. The succinate produced is converted to carbohydrates via phosphoenolpyruvate carboxykinase and to amino acids via aminotransferases, while free organic acids may participate in acidifying the endosperm tissue, releasing stored starch into metabolism. The abundant organic acid in the scutellum was citrate, while malate concentration declined during the first three days of germination, and succinate concentration was low both in scutellum and endosperm. Malate was more abundant in endosperm tissue during the first three days of germination; before citrate became predominant, indicating that malate may be the main acid acidifying the endosperm. The operation of the glyoxylate cycle coincided with an increase in the ATP/ADP ratio, a buildup of H2O2 and changes in the redox state of ascorbate and glutathione. It is concluded that operation of the glyoxylate cycle in the scutellum of cereals may be important not only for conversion of fatty acids to carbohydrates, but also for the acidification of endosperm and amino acid synthesis.

Topics: Adenosine Diphosphate; Adenosine Triphosphate; Alanine Transaminase; Amino Acids; Ascorbic Acid; Endosperm; Fumarate Hydratase; Germination; Glutathione; Glyoxylates; Hordeum; Phosphoenolpyruvate Carboxylase; Seeds; Succinate Dehydrogenase

In recent years, interest in tomato breeding for enhanced antioxidant content has increased as medical research has pointed to human health benefits from antioxidant dietary intake. Ascorbate is one of the major antioxidants present in tomato, and little is known about mechanisms governing ascorbate pool size in this fruit. In order to provide further insights into genetic mechanisms controlling ascorbate biosynthesis and accumulation in tomato, we investigated the fruit transcriptome profile of the Solanum pennellii introgression line 10-1 that exhibits a lower fruit ascorbate level than its cultivated parental genotype. Our results showed that this reduced ascorbate level is associated with an increased antioxidant demand arising from an accelerated oxidative metabolism mainly involving mitochondria, peroxisomes, and cytoplasm. Candidate genes for controlling ascorbate level in tomato fruit were identified, highlighting the role of glycolysis, glyoxylate metabolism, and purine breakdown in modulating the ascorbate pool size.

Topics: Antioxidants; Ascorbic Acid; Chromosome Mapping; Citric Acid Cycle; Fruit; Gene Expression Profiling; Gene Expression Regulation, Plant; Genes, Plant; Glycolysis; Glyoxylates; Oligonucleotide Array Sequence Analysis; Oxidation-Reduction; Peroxisomes; Phenotype; Quantitative Trait Loci; Solanum; Solanum lycopersicum; Species Specificity

Using a gas-chromatographic method, we examined the effects of phosphate concentration, added calcium chloride, and pH on precipitation of oxalate from urine. All three factors are important, but the pH of precipitation is particularly so, especially in the presence of even normal concentrations of ascorbic acid. At pH 8, increases in measured oxalate ranged from 20% at an ascorbic acid concentration of 1 mmol/L to more than 300% at 15 mmol/L. Ascorbic acid is rapidly converted to oxalate at alkaline pH. We also investigated the stability of both untreated and acidified urine containing ascorbic acid during storage for up to one month at -70, -20, and 4 degrees C, and room temperature. After one month, untreated collections were stable at -70 degrees C and acidified collections at -20 and -70 degrees C. We recommend conditions for assay and storage of urine specimens that are to be assayed for oxalate under which positive interference by ascorbic acid is minimized.

Topics: Ascorbic Acid; Calcium Chloride; Chemical Precipitation; Chromatography, Gas; False Positive Reactions; Female; Glycolates; Glyoxylates; Humans; Hydrogen-Ion Concentration; Oxalates; Phosphates; Specimen Handling