title: Characterization of benzo(a)pyrene hydroxylase of trout liver.
abstract: Trout liver microsomes contained as 0.40 nmole of cytochrome P-450 per mg of protein and a NADPH-cytochrome c reductase activity of 23 nmoles of cytochrome c reduced per mg of protein per min at 22 degrees. Associated with these was a high benzo(a)pyrene hydroxylase activity, which required NADPH and O2 and was inhibited by CO. With thin-layer chromatography, at least five metabolites could be identified (including dihydrodiols, phenols, and quinones of benzo(a)pyrene). Inhibitors such as 2-diethylaminoethyl-2,2-diphenylvalerate, aminopyrine, metyrapone, pyridine, n-octylamine, and 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane were relatively ineffective in inhibiting trout benzo(a)pyrene hydroxylase. Typical inhibitors of 3-methylcholanthrene-induced cytochrome (P-448), such as alpha-naphthoflavone, zoxazolamine, and testosterone, were effective, however. With benzo(a)pyrene it was possible to induce type I spectral change in trout cytochrome P-450. In spite of the many enzymatic characteristics of cytochrome P-448, trout cytochrome P-450 had maximum absorbance at 450.6 nm. when in reduced form and complexed with CO. the ethyl isocyanide gave an interaction spectrum with reduced trout liver cytochrome P-450 resembling that of control rat.
mesh_terms: D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000378:metabolism*; D001579:Benzopyrene Hydroxylase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D001580:Benzopyrenes / Q000378:metabolism; D002248:Carbon Monoxide / Q000494:pharmacology; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D008297:Male; D008748:Methylcholanthrene / Q000494:pharmacology; D008862:Microsomes, Liver / Q000201:enzymology*; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism; D011335:Proadifen / Q000494:pharmacology; D051381:Rats; D012487:Salmonidae / Q000378:metabolism*; D014337:Trout / Q000378:metabolism*
chemical_list: D001580:Benzopyrenes; D008748:Methylcholanthrene; D002248:Carbon Monoxide; D003577:Cytochrome P-450 Enzyme System; D011335:Proadifen; D001579:Benzopyrene Hydroxylase; D001189:Aryl Hydrocarbon Hydroxylases; D009251:NADPH-Ferrihemoprotein Reductase