title: Characterization of testosterone 16 alpha-hydroxylase (I-P-450(16) alpha) induced by phenobarbital in mice.
abstract: Cytochrome P-450 (I-P-450(16) alpha), which is associated with phenobarbital-induced testosterone 16 alpha-hydroxylation activity, was purified from livers of phenobarbital-treated female 129/J mice on the basis of the specific hydroxylation activity in fractions eluted from columns of octylamino-Sepharose 4B, hydroxylapatite, DEAE-Bio-Gel A, and isobutyl-Sepharose 4B. The specific cytochrome P-450 content of the purified I-P-450(16) alpha fraction was 12.4 nmol/mg of protein, and it had an apparent molecular weight of 54K. The specific activity of reconstituted testosterone 16 alpha-hydroxylation activity with the purified I-P-450(16) alpha fraction was 6-8 nmol min-1 (nmol of cytochrome P-450)-1. Rabbit antibody raised against the purified I-P-450(16) alpha fraction inhibited nearly 100% of the 16 alpha-hydroxylation activity in liver microsomes of phenobarbital-treated female 129/J mice but did not affect hepatic microsomal 16 alpha-hydroxylation activity of untreated male and female 129/J mice at all. In hepatic microsomes of phenobarbital-treated male 129/J mice, 70% of the 16 alpha-hydroxylation activity, at most, was catalyzed by I-P-450(16) alpha, and the residual 30% of the activity was catalyzed by C-P-450(16) alpha. The increase of I-P-450(16) alpha by phenobarbital was due to de novo synthesis of I-P-450(16) alpha, and this induction was not sexually regulated in 129/J mice. Anti-C-P-450(16) alpha [Harada, N., & Negishi, M. (1984) J. Biol. Chem. 259, 12285-12290] did not inhibit the 16 alpha-hydroxylation catalyzed by I-P-450(16) alpha; thus, I-P-450(16) alpha and C-P-450(16) alpha are immunochemically distinct isozymes of testosterone 16 alpha-hydroxylase.
mesh_terms: D000818:Animals; D000936:Antigen-Antibody Complex; D001189:Aryl Hydrocarbon Hydroxylases; D000072467:Cytochrome P450 Family 2; D004790:Enzyme Induction; D005260:Female; D007106:Immune Sera; D007700:Kinetics; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology*; D008970:Molecular Weight; D010634:Phenobarbital / Q000494:pharmacology*; D039181:Steroid 16-alpha-Hydroxylase; D013250:Steroid Hydroxylases / Q000096:biosynthesis* / Q000302:isolation & purification
chemical_list: D000936:Antigen-Antibody Complex; D007106:Immune Sera; D013250:Steroid Hydroxylases; D001189:Aryl Hydrocarbon Hydroxylases; C450239:CYP2C3 protein, Oryctolagus cuniculus; D000072467:Cytochrome P450 Family 2; D039181:Steroid 16-alpha-Hydroxylase; C022724:testosterone 7-alpha-hydroxylase, hamster; D010634:Phenobarbital