Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.6.99.3 (diaphorase)
 5,903 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In rat liver cell culture both benzanthracene and phenobarbitone induce the activity of benzypyrene hydrxylase while only phenobarbitone increases NADPH cytochrome c reductase activity. Benzpyrene hydroxylase but not NADPH cytochrome c reductase activity is dependent on the amino acid concentration of the culture medium in a similar manner to the regulation of the hepatic hydroxylase activity by dietary protein intake in the whole animal. Of all the amino acids present in the culture medium, only tryptophan induced benzpyrene hydroxylase when added singly to the medium. However, tryptophan also induced the activity of the reductase suggesting that its inducing effect is unrelated to raising the concentration of all the amino acids of the culture medium. It is proposed that tryptophan may only be an inducer because the cells have low levels of tryptophan pyrrolase activity.
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PMID:Effect of amino acids and inducers on the activity of the microsomal mono-oxygenase system in rat liver cell culture. 81 5

Three isomeric quinone metabolites of the environmental carcinogen benzo[a]pyrene undergo reversible, univalent oxidation-reduction cycles involving the corresponding benzo[a]pyrene diols and intermediate semiquinone radicals. Under anaerobic conditions, benzo[a]pyrene 1,6-dione, benzo[a]pyrene 3,6-dione, and benzo[a]pyrene 6,12-dione are readily reduced by mild biological agents such as NADH and glutathione. The benzo[a]pyrene diols, in turn, are very rapidly autooxidized to diones when exposed to air. Substantial amounts of hydrogen peroxide are produced during these autooxidations. The benzo[a]pyrene diol/benzo[a]pyrene dione interconversions proceed by one-electron steps; the corresponding semiquinone radicals were detected as intermediates when the reactions were carried out at high pH. Benzo[a]pyrene diones are electron-acceptor substrates for NADH dehydrogenase. Catalytic amounts of these metabolites, together with this respiratory enzyme, function as cyclic oxidation-reduction couples to link NADH and molecular oxygen in the continuous production of hydrogen peroxide. Benzo[a]pyrene diones induce strand scissions when incubated with T7 DNA. The damage is modified by conditions that indicate that reduced oxygen species propagate the reactions responsible for strand scission. Benzo[a]pyrene diones are cytotoxic at low concentrations to cultured hamster cells. The cytotoxic effect can be substantially reduced by depletion of oxygen from the growth medium and the atmosphere in which the cells are incubated. The results support the hypothesis that the biological activity of benzo[a]pyrene diones is due to the regenerative oxidation-reduction cycles involving quinone and hydroquinone forms; activated oxygen species and semiquinone radicals formed during these cycles are most likely responsible for the observed cytotoxic action. The role of activated oxygen species in carcinogenesis is discussed.
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PMID:Benzo[a]pyrene dione-benzo[a]pyrene diol oxidation-reduction couples; involvement in DNA damage, cellular toxicity, and carcinogenesis. 300 1