title: Evidence of direct generation of oxygen free radicals from heterocyclic amines by NADPH/cytochrome P-450 reductase in vitro.
abstract: Highly purified cytochrome P-450 reductase (also called cytochrome c reductase; EC 1.6.2.4.) and NADPH were used to generate superoxide radical (O2.-) from 11 different heterocyclic amines (HCAs) as identified by electron spin resonance spectroscopy using the spin trapping method with 5,5-dimethyl-1-pyrroline N-oxide (DMPO). The signal intensity of DMPO-OOH(-O2-) (i.e., the DMPO spin adduct of O2.-) was strongest for 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ). The O2.- generation with HCAs decreased in the following order: 2-amino-3,8-dimethyl-imidazo[4,5-f]quinoxaline (MeIQx) = 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) > 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (diMeIQx) > or = other HCAs; O2.- generation was lowest with 2-amino-3-methyl-9H-pyrido[2,3-b]indole .CH3COOH (MeA alpha C). By using Lineweaver-Burk plots, Km values of cytochrome P-450 reductase for mitomycin C, IQ, and MeIQ were determined to be 1.60 x 10(-6) M, 1.97 x 10(-5) M, and 2.83 x 10(-6) M, respectively. The present findings have important implications for carcinogenesis because of the known effect of oxygen radicals on cell proliferation.
authors.affiliation: Department of Microbiology, Kumamoto University School of Medicine.
authors.forename: K
authors.initials: K
authors.lastname: Sato
authors.forename: T
authors.initials: T
authors.lastname: Akaike
authors.forename: Y
authors.initials: Y
authors.lastname: Kojima
authors.forename: M
authors.initials: M
authors.lastname: Ando
authors.forename: M
authors.initials: M
authors.lastname: Nagao
authors.forename: H
authors.initials: H
authors.lastname: Maeda
mesh_terms: D000588:Amines / Q000378:metabolism*; D003497:Cyclic N-Oxides / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004247:DNA / Q000187:drug effects / Q000235:genetics; D004578:Electron Spin Resonance Spectroscopy; D006571:Heterocyclic Compounds / Q000378:metabolism*; D006900:Hydroxylation; D007700:Kinetics; D006899:Mixed Function Oxygenases / Q000378:metabolism; D009152:Mutagenicity Tests; D009153:Mutagens / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism*; D004369:Pentetic Acid / Q000378:metabolism; D011804:Quinolines / Q000378:metabolism; D011810:Quinoxalines / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013481:Superoxides / Q000378:metabolism
chemical_list: D000588:Amines; D003497:Cyclic N-Oxides; D006571:Heterocyclic Compounds; D009153:Mutagens; D011804:Quinolines; D011810:Quinoxalines; D017382:Reactive Oxygen Species; D013481:Superoxides; D009249:NADP; C017245:5,5-dimethyl-1-pyrroline-1-oxide; C036990:2-amino-3,8-dimethylimidazo(4,5-f)quinoxaline; D004369:Pentetic Acid; D004247:DNA; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D009251:NADPH-Ferrihemoprotein Reductase; C036989:2-amino-3,4-dimethylimidazo(4,5-f)quinoline