Relationship between the reduction of oxygen, artificial acceptors and cytochrome P-450 by NADPH--cytochrome c reductase.
The interaction of NADPH--cytochrome c reductase with oxygen, artificial acceptors and cytochrome P-450 was studied. The generation of superoxide anion radicals (O2-.) from the oxidation of adrenaline to adrenochrome catalysed by NADPH--cytochrome c reductase proceeds independently of the interaction of the enzyme with the artificial anaerobic acceptors cytochrome c or 2,6-dichlorophenol-indophenol. Propyl 3,4,5-trihydroxybenzoate inhibited competitively the adrenaline oxidation by isolated NADPH--cytochrome c reductase (Ki 3.2--4.7 micrometer) and inhibited non-competitively the cytochrome c reduction (Ki 92--109 micrometer). In contrast with the process of electron transfer to cytochrome c, the rate of reduction of cytochrome P-450 and the rate of oxidation of adrenaline in liver microsomal fraction are correlated. Hexobarbital increases the Vmax. of adrenaline oxidation without affecting the Km value, whereas metyrapone, a metabolic inhibitor decreases Vmax. without affecting the Km. From the results obtained, some conclusions about NADPH--cytochrome c reductase function were made.
D015086:2,6-Dichloroindophenol / Q000378:metabolism; D000818:Animals; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D003579:Cytochrome Reductases / Q000378:metabolism*; D003574:Cytochrome c Group / Q000378:metabolism; D004837:Epinephrine / Q000378:metabolism; D006591:Hexobarbital / Q000494:pharmacology; D062385:Hydroxybenzoates / Q000494:pharmacology; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D008797:Metyrapone / Q000494:pharmacology; D008862:Microsomes, Liver / Q000201:enzymology*; D009251:NADPH-Ferrihemoprotein Reductase / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D051381:Rats
D003574:Cytochrome c Group; D062385:Hydroxybenzoates; D003577:Cytochrome P-450 Enzyme System; D006591:Hexobarbital; D015086:2,6-Dichloroindophenol; D003579:Cytochrome Reductases; D009251:NADPH-Ferrihemoprotein Reductase; D004837:Epinephrine; D008797:Metyrapone