Active complex between adrenodoxin reductase and adrenodoxin in the cytochrome P-450scc reduction reaction.
In order to elucidate the mechanism of the electron transfer reaction of mitochondrial steroid hydroxylase, the reduction reaction of cytochrome P-450scc (P-450scc) catalyzed by covalently cross-linked complexes between adrenodoxin reductase (AR) and adrenodoxin (AD) was studied. The reduction rate with the covalent AR-AD complex was very slow (0.030 min-1, as the flavin turnover number) compared with the reduction catalyzed by AR and AD (4.6 min-1). When free AD was added to the reaction mixture containing the AR-AD complex, the rate increased about 30 times. The AD dimer [(AD)2], and a complex between AR and the AD dimer [AR-(AD)2] were then prepared. The Vmax for the P-450scc reduction activity of AR with (AD)2 was 50% of that of AR with AD. The Km value for the total concentration of AD in the P-450scc reduction reaction mixture containing AR and (AD)2 was found to be the same as that in the reaction mixture containing AR and AD. P-450scc reduction by AR-(AD)2 was about 5 times faster than that by AR-AD. The addition of free AD to the AR-(AD)2 complex enhanced the P-450scc reduction about 30 times. AR-AD and AR-(AD)2 were able to reduce external AD, cytochrome c, and acetylated cytochrome c.(ABSTRACT TRUNCATED AT 250 WORDS)
Hara
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T
Department of Food and Nutrition, Nakamura Gakuen College, Fukuoka.
Kimura
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D000325:Adrenodoxin / Q000378:metabolism*; D002786:Cholesterol Side-Chain Cleavage Enzyme / Q000302:isolation & purification / Q000378:metabolism*; D004579:Electron Transport; D004591:Electrophoresis, Polyacrylamide Gel; D005287:Ferredoxin-NADP Reductase / Q000378:metabolism*; D007700:Kinetics; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism*; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism; D010084:Oxidation-Reduction
D000325:Adrenodoxin; D002786:Cholesterol Side-Chain Cleavage Enzyme; D005287:Ferredoxin-NADP Reductase; D009247:NADH, NADPH Oxidoreductases; D009251:NADPH-Ferrihemoprotein Reductase