Hydroxylation of aniline and aminoantipyrine derivatives (1-phenyl-2,3-dimethylaminopyrazolon-5) in liver endoplasmic reticulum
Archakov, A.I.; Karuzina, I.I.; Tveritinov, V.N.; Kokareva, I.S.
Biokhimiia 40(1): 32-39
1975
ISSN/ISBN: 0320-9725 PMID: 1139001 Document Number: 95552
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. Km is not a characteristic of the affinity of cytochrome P-450 to substrates. The calculations were made to show that cytochrome P-450 formed two types of the enzyme-substrate complexes containing one or two substrate molecules. The complex in which one molecule of cytochrome P-450 binds one substrate molecule is considered to be active.