title: [Interaction of coumarin-hydroxylating cytochrome P-450coh from liver microsomes of mice induced by pyrazole with cytochrome b5].
abstract: Cytochrome P-450coh from pyrazole-treated mice was shown to form a tight and specific complex with cytochrome b5 from mouse liver microsomes. The complex formation was found to result in type I spectral changes indicating a spin shift from the low to the high spin form. When added to a reconstituted system containing cytochrome P-450coh, NADPH-cytochrome P-450 reductase and phospholipid, cytochrome b5 stimulates hydroxylation of coumarin and O-deethylation of 7-ethoxycoumarin. The maximal stimulating effect is reached at a 1:1 stoichiometry. Mouse liver cytochrome b5 stimulates hydroxylation and deethylation by 100% and 60%, respectively. The stimulating effect of cytochrome b5 was found to result from the increase of the maximal rate of oxidation, being practically without effect on Km. Cytochrome b5 purified from rat and rabbit liver microsomes interacts with cytochrome P-450coh but fails to stimulate the oxidation reaction. At large excess, cytochrome b5 inhibits the oxidations catalyzed by cytochrome P-450coh. Immobilized cytochrome b5 either from mouse or rat and rabbit microsomes proved to be an efficient affinity matrix for cytochrome P-450coh purification.
authors.forename: S A
authors.initials: SA
authors.lastname: Usanov
authors.forename: P
authors.initials: P
authors.lastname: Honkakoski
authors.forename: M
authors.initials: M
authors.lastname: Lang
authors.forename: O
authors.initials: O
authors.lastname: Hanninen
mesh_terms: D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases; D002384:Catalysis; D002846:Chromatography, Affinity; D065637:Cytochrome P-450 CYP2A6; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis / Q000378:metabolism*; D015786:Cytochromes b5 / Q000378:metabolism*; D004790:Enzyme Induction; D007700:Kinetics; D051379:Mice; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology*; D006899:Mixed Function Oxygenases / Q000096:biosynthesis / Q000378:metabolism*; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism; D010084:Oxidation-Reduction; D011720:Pyrazoles / Q000494:pharmacology*
chemical_list: D011720:Pyrazoles; C031280:pyrazole; D015786:Cytochromes b5; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D001189:Aryl Hydrocarbon Hydroxylases; D065637:Cytochrome P-450 CYP2A6; D009251:NADPH-Ferrihemoprotein Reductase
vernacular_title: Vzaimodeĭstvie kumaringidroksiliruiushchego tsitokhroma P-450coh mikrosom pecheni mysheĭ, indutsirovannykh pirazolom, s thitokhromom B5.