[Kinetics of formation of the enzyme-substrate complexes of cytochrome P-450 in rat liver microsomes].

A spectrophotometric study of the kinetics of binding of I and II type substrates to cytochrome P-450 from rat liver microsomes has been carried out. The rates of binding of the substrates of type I to a low spin form of the enzyme and those of substrates of type II to a high spin form are approximately the same. The interaction of type II substrates with a low spin form of cytochrome P-450 occurs at a 15--20-fold lower rate.

[Hydroxylation of aniline and aminoantipyrine derivatives (1-phenyl-2,3-dimethylaminopyrazolon-5) in liver endoplasmic reticulum].

The absence of correlation between the effect of aniline and aminoantipyrine derivatives on cytochrome P-450 reduction rate and its oxidation rate draw to the conclusion that the reductase reaction is not a limiting step of hydroxylation for all substrates. Km is found to be directly proportional to Vmax of hydroxylated substrates. Hence, in these reactions the Km value is determined not by the value Ks but by the kappa+2/kappa+1 ratio.