title: Purification and properties of cytochrome P-450 generally acting as a catalyst on benzo[a]pyrene hydroxylation from liver microsomes of untreated rats.
abstract: A form of cytochrome P-450 generally catalyzing benzo[a]pyrene (B[a]P) hydroxylation was purified from liver microsomes of untreated rats on the basis of the catalytic activity. The purification procedures consisted of cholate solubilization and chromatography in 3 steps, on DEAE-Toyopearl (at room temperature), hydroxylapatite, and CM-Toyopearl columns. Cytochrome P-450 purified in this way (named P-450/B[a]P) was homogeneous on SDS-polyacrylamide gel electrophoresis, and the molecular weight was estimated to be 51,000. The absorption spectra of the oxidized form of P-450/B[a]P showed a Soret peak at 417 nm, characteristic of low-spin hemoprotein, and the Soret peak of the reduced cytochrome P-450-CO complex was at 451 nm. Immunochemical analysis of P-450/B[a]P indicated that P-450/B[a]P is immunologically distinct from P-450b (a major phenobarbital-inducible form of P-450) and P-450c (a major 3-methylcholanthrene-inducible form of P-450, which highly catalyzes the hydroxylation of B[a]P). B[a]P hydroxylase activity in liver microsomes of untreated rats was inhibited to about 20% by the P-450/B[a]P antibody. These results demonstrate that P-450/B[a]P is a different form of P-450 from P-450b and P-450c, and generally catalyzes B[a]P hydroxylation in liver microsomes of untreated rats.
authors.affiliation: Department of Veterinary Biochemistry, School of Veterinary Medicine, Rakuno Gakuen University, Hokkaido.
authors.forename: N
authors.initials: N
authors.lastname: Ohgiya
authors.forename: H
authors.initials: H
authors.lastname: Yokota
authors.forename: A
authors.initials: A
authors.lastname: Yuasa
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000378:metabolism*; D001579:Benzopyrene Hydroxylase / Q000378:metabolism*; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003577:Cytochrome P-450 Enzyme System / Q000032:analysis / Q000302:isolation & purification*; D004058:Diffusion; D004591:Electrophoresis, Polyacrylamide Gel; D005779:Immunodiffusion; D066298:In Vitro Techniques; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology*; D006899:Mixed Function Oxygenases / Q000378:metabolism; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism; D010084:Oxidation-Reduction; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D001579:Benzopyrene Hydroxylase; D001189:Aryl Hydrocarbon Hydroxylases; D009251:NADPH-Ferrihemoprotein Reductase