Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0003969 (vitamin C deficiency)
 625 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Among nutrients, the role of water-soluble vitamins as genetic expression modulators has not been exhaustively stu-died. Relevant information is shown herein on the present state of the art in this field. For example, vitamin C deficiency leads to a decrease in mRNA levels of apolipoprotein A1 (Apo A1) in liver. Biotin participates in the regulation, both at mRNA and protein level, of the enzymes that participate in its own metabolic cycle and of enzymes that contribute to glucose metabolism. Thiamine regulates the expression of some genes that code for enzymes using thiamine diphosphate as cofactor. Thiamine deficiency diminishes the mRNA levels of transketolase and pyruvate dehydrogenase. It has been shown in riboflavin-deficient rats that FAD regulates some acetyl CoA dehydrogenases, producing a marked increase in mRNA levels. Nicotinamide positively regulates glyceraldehyde-3-phosphate dehydrogenase when NADH is added. Vitamin B6 modulates the expression of a variety of genes that respond to hormones. Vitamin B12 increases concentrations of the enzymatic protein methionine synthetase and doe not affect mRNA levels, which implies that this protein is regulated by its cofactor post-transcriptionally. Most mechanisms involved in these regulation examples are not known, which opens new research areas for the future.
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PMID:[Importance of water-soluble vitamins as regulatory factors of genetic expression]. 1199 11

Vitamin C, a reducing agent and antioxidant, is a cofactor in reactions catalyzed by Cu(+)-dependent monooxygenases and Fe(2+)-dependent dioxygenases. It is synthesized, in vertebrates having this capacity, from d-glucuronate. The latter is formed through direct hydrolysis of uridine diphosphate (UDP)-glucuronate by enzyme(s) bound to the endoplasmic reticulum membrane, sharing many properties with, and most likely identical to, UDP-glucuronosyltransferases. Non-glucuronidable xenobiotics (aminopyrine, metyrapone, chloretone and others) stimulate the enzymatic hydrolysis of UDP-glucuronate, accounting for their effect to increase vitamin C formation in vivo. Glucuronate is converted to l-gulonate by aldehyde reductase, an enzyme of the aldo-keto reductase superfamily. l-Gulonate is converted to l-gulonolactone by a lactonase identified as SMP30 or regucalcin, whose absence in mice leads to vitamin C deficiency. The last step in the pathway of vitamin C synthesis is the oxidation of l-gulonolactone to l-ascorbic acid by l-gulonolactone oxidase, an enzyme associated with the endoplasmic reticulum membrane and deficient in man, guinea pig and other species due to mutations in its gene. Another fate of glucuronate is its conversion to d-xylulose in a five-step pathway, the pentose pathway, involving identified oxidoreductases and an unknown decarboxylase. Semidehydroascorbate, a major oxidation product of vitamin C, is reconverted to ascorbate in the cytosol by cytochrome b(5) reductase and thioredoxin reductase in reactions involving NADH and NADPH, respectively. Transmembrane electron transfer systems using ascorbate or NADH as electron donors serve to reduce semidehydroascorbate present in neuroendocrine secretory vesicles and in the extracellular medium. Dehydroascorbate, the fully oxidized form of vitamin C, is reduced spontaneously by glutathione, as well as enzymatically in reactions using glutathione or NADPH. The degradation of vitamin C in mammals is initiated by the hydrolysis of dehydroascorbate to 2,3-diketo-l-gulonate, which is spontaneously degraded to oxalate, CO(2) and l-erythrulose. This is at variance with bacteria such as Escherichia coli, which have enzymatic degradation pathways for ascorbate and probably also dehydroascorbate.
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PMID:Vitamin C. Biosynthesis, recycling and degradation in mammals. 1722 74