title: Metabolic activation of carcinogenic 1-nitropyrene by human cytochrome P450 1B1 in Salmonella typhimurium strain expressing an O-acetyltransferase in SOS/umu assay.
abstract: Metabolic activation of 1-nitropyrene (1-NP) by human cytochrome P450 (P450) family 1 enzymes co-expressed with NADPH-cytochrome P450 reductase (NPR) in Escherichia coli membranes was investigated. 1-NP induced umu gene expression in Salmonella typhimurium TA1535/pSK1002 in the absence of any P450 system, but the activities were influenced by the levels of bacterial O-acetyltransferase (OAT) and nitroreductase. Metabolic activation of 1-NP by human P450 1B1/NPR membranes was observed and was influenced by the levels of OAT levels in tester strains. Metabolic activation of 1-NP (0.3microM) by P450 1B1 was 750 umu units/min/nmol P450 1B1 in an OAT-overexpressing strain NM2009. The metabolic activation of 1-NP (3-30microM) was similar (approximately 300 umu units/min/nmol P450 1B1) using TA1535/pSK1002 or OAT-deficient strain NM2000. P450 1B1 had the highest catalytic activities among P450 family 1 enzymes for the activation of 1-aminopyrene (1-AP) in the OAT-overexpressing strain NM2009, suggesting nitrenium ion formation via N-hydroxylation/O-acetylation. High-performance liquid chromatography (HPLC) analyses revealed the formation of 1-nitropyrene-6-ol and also 1-nitropyrene-3-ol, 1-nitropyrene-8-ol, and trans-4,5-dihydroxy-4,5-diol-1-nitropyrene from 1-NP (10microM), catalyzed by P450 1B1. These results indicate that 1-NP can be activated by human P450 1B1 to a genotoxic agent by nitroreduction/O-acetylation at low substrate concentrations and probably by epoxidation (independent of OAT) at high concentrations.
authors.affiliation: Division of Drug Metabolism, Faculty of Pharmaceutical Sciences, Kanazawa University, 13-1 Takara-machi, 920-0934, Kanazawa, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Hatanaka
authors.forename: H
authors.initials: H
authors.lastname: Yamazaki
authors.forename: Y
authors.initials: Y
authors.lastname: Oda
authors.forename: F P
authors.initials: FP
authors.lastname: Guengerich
authors.forename: M
authors.initials: M
authors.lastname: Nakajima
authors.forename: T
authors.initials: T
authors.lastname: Yokoi
mesh_terms: D000123:Acetyltransferases / Q000235:genetics / Q000378:metabolism; D001189:Aryl Hydrocarbon Hydroxylases; D001711:Biotransformation; D002273:Carcinogens / Q000493:pharmacokinetics* / Q000633:toxicity*; D065633:Cytochrome P-450 CYP1B1; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics; D006801:Humans; D066298:In Vitro Techniques; D008862:Microsomes, Liver / Q000378:metabolism; D009153:Mutagens / Q000493:pharmacokinetics* / Q000633:toxicity*; D009251:NADPH-Ferrihemoprotein Reductase / Q000235:genetics / Q000378:metabolism; D011721:Pyrenes / Q000493:pharmacokinetics* / Q000633:toxicity*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013014:SOS Response, Genetics; D012486:Salmonella typhimurium / Q000187:drug effects / Q000235:genetics / Q000378:metabolism
chemical_list: D002273:Carcinogens; D009153:Mutagens; D011721:Pyrenes; D011994:Recombinant Proteins; D003577:Cytochrome P-450 Enzyme System; D001189:Aryl Hydrocarbon Hydroxylases; C585496:CYP1B1 protein, human; D065633:Cytochrome P-450 CYP1B1; D009251:NADPH-Ferrihemoprotein Reductase; D000123:Acetyltransferases; C004482:1-aminopyrene; C032668:1-nitropyrene