title: Nitroreductase activity of heart lipoamide dehydrogenase.
abstract: A novel reaction catalysed by lipoamide dehydrogenase is described. In the presence of NADH, lipoamide dehydrogenase reduces the nitro group of 4-nitropyridine and 4-nitropyridine N-oxide. The elution profiles from a DEAE-cellulose column for the dehydrogenase and nitroreductase activities are identical. Chemical modifications of critical amino acid residues suggest that the two activities share a common catalytic domain. Nitro reduction catalysed by lipoamide dehydrogenase was monitored spectrophotometrically and chromatographically. The major product from the enzymic reduction of 4-nitropyridine was isolated and characterized structurally as NN-bis(pyridinyl)hydroxylamine, which is formed presumably via 4-hydroxyaminopyridine in a four-electron redox reaction.
mesh_terms: D000818:Animals; D002848:Chromatography, DEAE-Cellulose; D002855:Chromatography, Thin Layer; D003497:Cyclic N-Oxides / Q000378:metabolism; D008058:Dihydrolipoamide Dehydrogenase / Q000378:metabolism*; D007700:Kinetics; D009206:Myocardium / Q000201:enzymology*; D009243:NAD / Q000378:metabolism; D009601:Nitroreductases / Q000378:metabolism*; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000378:metabolism*; D011725:Pyridines / Q000378:metabolism; D013053:Spectrophotometry; D013552:Swine
chemical_list: D003497:Cyclic N-Oxides; D011725:Pyridines; D009243:NAD; C052728:4-nitropyridine; D010088:Oxidoreductases; D009601:Nitroreductases; D008058:Dihydrolipoamide Dehydrogenase; C013620:4-nitropyridine 1-oxide