title: Resolution of two forms of cytochrome P-450 from liver microsomes of rabbit treated with 2,3,7,8-tetrachlorodibenzo-p-dioxin.
abstract: Two forms of cytochrome P-450 with different substrate specificities were isolated from liver microsomes of rabbits treated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). A specific antibody was produced toward the major form of the cytochrome. The antibody inhibits microsomal acetanilide hydroxylation (80%). It does not cross-react with the minor fraction of the cytochrome or inhibit the hydroxylation of 3,4-benzpyrene or coumarin, the N-demethylation of aminopyrine or the O-deethylation of 7-ethoxycoumarin catalyzed by rabbit liver microsomes. The major form has an estimated Mr = 54,000 and displays an n-octylamine difference spectrum with an absorption maximum at 426 nm and a minimum at 391 nm. When reconstituted, this cytochrome catalyzes acetanilide hydroxylation at a higher rate than microsomes or the minor fraction. The n-octylamine difference spectrum of the minor fraction displays an absorption maximum at 431 nm and a minimum at 410 nm. When reconstituted, this fraction catalyzes the hydroxylation of 3,4-benzpyrene and the O-deethylation of 7-ethoxycoumarin. The two cytochromes appear to be distinct entities and function in different catalytic pathways.
mesh_terms: D000083:Acetanilides / Q000378:metabolism; D000632:Aminopyrine / Q000378:metabolism; D000818:Animals; D000917:Antibody Formation; D001580:Benzopyrenes / Q000378:metabolism; D002384:Catalysis; D003374:Coumarins / Q000378:metabolism; D003429:Cross Reactions; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000276:immunology / Q000302:isolation & purification*; D003640:Dealkylation; D004147:Dioxins / Q000494:pharmacology*; D006900:Hydroxylation; D007700:Kinetics; D008099:Liver / Q000187:drug effects; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology*; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism; D000072317:Polychlorinated Dibenzodioxins / Q000494:pharmacology*; D011817:Rabbits; D013329:Structure-Activity Relationship
chemical_list: D000083:Acetanilides; D001580:Benzopyrenes; D003374:Coumarins; D065607:Cytochrome P-450 Enzyme Inhibitors; D004147:Dioxins; D000072317:Polychlorinated Dibenzodioxins; D000632:Aminopyrine; D003577:Cytochrome P-450 Enzyme System; D009251:NADPH-Ferrihemoprotein Reductase