Direct evidence for electron transfer from ferrous cytochrome b5 to the oxyferrous intermediate of liver microsomal cytochrome P-450 LM2.

摘要: Interaction and electron transfer between highly purified microsomal cytochrome P-450 from phenobarbital-induced rabbits b5 uninduced was investigated by difference stopped-flow spectrophotometry. Formation of a 1:1 complex ferric b5, demonstrated spectrophotometry, observed only when both cytochromes were incorporated into micelles phosphatidylcholine. The dissociation constant (Kd) the decreased 2.3 microM to 0.4 in presence 1 mM benzphetamine. apparent Kd benzphetamine reduced 220 50 upon addition b5. influence ferrous on autooxidation oxyferrous intermediate absence substrate Both photochemically, so that experiments could be carried out corresponding reductases pyridine nucleotides. Kinetic analysis data showed formation prerequisite for cytochromes. Here again, incorporation absolutely required this process. 7.5 2.2 rate P-450, derived kinetics reoxidation either or increased 2.5 s-1 about 4 7 These results provide first quantitative whose is compatible with observations made effect hydroxylation reactions catalyzed enzyme system.