The properties of cytochrome P-450 and hydroxylase activity of reconstituted proteoliposomal membranes.

Type I substrates are bound to soluble cytochrome P-450 worse than to microsomes. The incorporation of haemoprotein into phosphatidylcholine liposomes restores the capability of isolated cytochrome P-450 to interact with such substrates as well as the microsomal form. The soluble and lipid-binding cytochrome P-450 does not differ in its thermal stability and protease digestion. Liposome-bound cytochrome P-450 has a higher dimethylaniline, aniline and p-nitroanisole hydroxylase activity than its soluble form. Only the aniline hydroxylase activity of microsomal, proteoliposomal and soluble cytochrome P-450 was inhibited by tyrosine . copper (II) complex with NADPH or cumene hydroperoxide as cosubstrates. The inhibitory action of the Tyr2-Cu2+ complex on the other hydroxylase activities depended on the cytochrome P-450 forms and the type of cosubstrates and substrates used.