NADPH-dependent flavoenzymes catalyze one electron reduction of metal ions and molecular oxygen and generate hydroxyl radicals.
This study reports a new property of the important NAD(P)H-dependent flavoenzymes, glutathione reductase, lipoyl dehydrogenase and ferredoxin-NADP+ oxidoreductase, that can catalyze a one electron reduction of metal ions such as chromium(VI) and vanadium(V). During the enzymatic reduction process, molecular oxygen is reduced to H2O2, which reacts with the reduced metal complexes to generate hydroxyl radicals. Since the hydroxyl radicals have been suggested to play an important role in Cr(VI) toxicity, this study provides a basis for a recent observation that Cr(VI) mutagenesis is strongly oxygen dependent. These results also point to an enzymatic pathway for the metabolism of some metal ions and concomitant generation of hydroxyl radicals.
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Department of Chemistry, West Virginia University, Morgantown 29506.
Dalal
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D000818:Animals; D002417:Cattle; D003013:Clostridium / Q000201:enzymology; D008058:Dihydrolipoamide Dehydrogenase / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D004579:Electron Transport; D005287:Ferredoxin-NADP Reductase / Q000378:metabolism*; D005420:Flavoproteins / Q000378:metabolism*; D005609:Free Radicals; D005980:Glutathione Reductase / Q000378:metabolism*; D006878:Hydroxides / Q000378:metabolism*; D017665:Hydroxyl Radical; D007413:Intestinal Mucosa / Q000201:enzymology; D007700:Kinetics; D009249:NADP / Q000378:metabolism*; D010084:Oxidation-Reduction; D010944:Plants / Q000201:enzymology
D005420:Flavoproteins; D005609:Free Radicals; D006878:Hydroxides; D017665:Hydroxyl Radical; D009249:NADP; D005287:Ferredoxin-NADP Reductase; D008058:Dihydrolipoamide Dehydrogenase; D005980:Glutathione Reductase