title: Purification and characterization of a form of cytochrome P450 from bear liver microsomes.
abstract: A form of P450 [termed P450(b-1)] was purified from male bear liver microsomes. The specific content of the final P450(b-1) preparation was 11.26 nmol/mg protein, and recovery was 0.20% of the microsomal P450. The apparent molecular weight of P450(b-1) was 54,000. The absorption spectrum of P450(b-1) indicated that this protein was a low- and high-spin mixed type P450 in the oxidized form. The carbon monoxide complex of reduced P450(b-1) showed an absorption peak at 450.5 nm. The reconstituted system containing P450(b-1) catalyzed the metabolism of aminopyrine, benzo[a]pyrene, 7-ethoxycoumarin, imipramine and propranolol, of which P450(b-1) most strongly catalyzed aminopyrine N-demethylation and imipramine N-demethylation. The N-terminal amino acid sequence of P450(b-1) was highly homologous to that of P450-D1 from liver microsomes of male beagle dogs. P450(b-1) showed similarities in spectral properties, N-terminal amino acid sequence, and catalytic activities to rat P450 2C11. P450(b-1) was immunochemically cross-reactive with anti-P450 2C11 antibody and very weakly cross-reactive with anti-P450 2E1 antibody, but did not react with anti P450 1A1 or 2B1 antibodies. On the basis of these results, we suggest that P450(b-1) belongs to the P450 2C subfamily.
authors.affiliation: Department of Toxicology, Faculty of Veterinary Medicine, Hokkaido University, Sapporo, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Yamamoto
authors.forename: M
authors.initials: M
authors.lastname: Masuda
authors.forename: A
authors.initials: A
authors.lastname: Kazusaka
authors.forename: S
authors.initials: S
authors.lastname: Imaoka
authors.forename: Y
authors.initials: Y
authors.lastname: Funae
authors.forename: S
authors.initials: S
authors.lastname: Fujita
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry / Q000302:isolation & purification*; D007527:Isoenzymes / Q000737:chemistry / Q000302:isolation & purification*; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology*; D008969:Molecular Sequence Data; D001503:Ursidae / Q000378:metabolism*
chemical_list: D007527:Isoenzymes; D003577:Cytochrome P-450 Enzyme System