title: Rat hepatic cytochrome P-450 isoenzyme 2c. Identification as a male-specific, developmentally induced steroid 16 alpha-hydroxylase and comparison to a female-specific cytochrome P-450 isoenzyme.
abstract: Rat hepatic cytochrome P-450 isoenzyme 2c, purified to homogeneity from uninduced, adult rat liver (Waxman, D.J., Ko, A., and Walsh, C. (1983) J. Biol. Chem. 258, 11937-11947), was shown to exhibit a unique NH2-terminal amino acid sequence as well as distinctive peptide maps and immunochemical properties when compared to seven other purified rat liver P-450 isoenzymes. P-450 2c was an efficient monooxygenase catalyst with several xenobiotic substrates; P-450 2c also catalyzed 16 alpha- and 2 alpha-hydroxylations of testosterone, androst-4-ene-3,17-dione and progesterone (total turnover = 7-9 min-1 P-450(-1) at 25 microM steroid substrate) with the ratio of 2 alpha to 16 alpha hydroxylation varying from less than or equal to 0.02 to 1.6 depending on the steroid's C-17 substituent. Six different microsomal steroid hydroxylase activities characteristic of purified P-450 2c and sensitive to specific inhibition by anti-P-450 2c antibody were induced at puberty in male but not female rat liver. Microsomal steroid hydroxylations catalyzed by other P-450 isoenzymes exhibited age and sex dependencies distinct from those of the P-450 2c-mediated activities. Immunochemical analyses confirmed that this sex dependence and developmental induction reflected alterations in P-450 2c polypeptide levels. Attempts to chromatographically detect P-450 2c in either immature male or adult female microsomes were unsuccessful and led to purification of P-450 2d (female), a catalytically distinct and female-specific form. Peptide mapping and immunochemical analyses suggested significant structural homologies between the two sex-specific isoenzymes, P-450 2c and P-450 2d (female). A significant suppression of P-450 2c levels (up to 70-80%) was observed upon administration of several classical P-450 inducers. These studies establish that P-450 2c corresponds to the male-specific and developmentally-induced steroid 16 alpha-hydroxylase of rat liver and suggest that the expression of P-450 2c versus P-450 2d (female) may provide a biochemical basis for the sex differences characteristic of rat liver xenobiotic metabolism.
mesh_terms: D000375:Aging; D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies; D000936:Antigen-Antibody Complex; D001189:Aryl Hydrocarbon Hydroxylases; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis* / Q000302:isolation & purification; D000072467:Cytochrome P450 Family 2; D004790:Enzyme Induction; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005779:Immunodiffusion; D007527:Isoenzymes / Q000096:biosynthesis / Q000302:isolation & purification; D007700:Kinetics; D008099:Liver / Q000254:growth & development; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology*; D008970:Molecular Weight; D010446:Peptide Fragments / Q000032:analysis; D051381:Rats; D011919:Rats, Inbred Strains; D012737:Sex Factors; D039181:Steroid 16-alpha-Hydroxylase; D013250:Steroid Hydroxylases / Q000096:biosynthesis*
chemical_list: D000906:Antibodies; D000936:Antigen-Antibody Complex; D007527:Isoenzymes; D010446:Peptide Fragments; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; D001189:Aryl Hydrocarbon Hydroxylases; C450279:CYP2C11 protein, rat; D000072467:Cytochrome P450 Family 2; D039181:Steroid 16-alpha-Hydroxylase