title: A new form of cytochrome P-450 responsible for mutagenic activation of 2-amino-3-methylimidazo[4,5-f]quinoline in human livers.
abstract: Antibodies to P-450IA2 strongly inhibited the mutagenic activation of 2-amino-3-methylimidazo [4,5-f]quinoline (IQ) and 3-amino-1-methyl-5H-pyrido[4,3-b]indole acetate but not aflatoxin B1 in human liver microsomes. The anti-rat P-450IA2 antibodies were capable of recognizing two proteins which show different mobilities on sodium dodecyl sulfate-polyacrylamide gel electrophoresis of human liver microsomes. A new form of cytochrome P-450 (designated P-450-HM4) cross-reactive with anti-rat P-450IA2 antibodies showing that the smaller molecular weight was purified from human liver microsomes by means of the fast-performance liquid chromatography system. The molecular weight of P-450-HM4 was estimated to be 49,000, which was apparently different from that of P-450PA (human P-450IA2). The antibodies to P-450-HM4 did not cross-react with P-450PA (human P-450IA2) but inhibited to various extents the mutagenic activation of IQ in microsomes from human livers. In addition, P-450-HM4 showed significant mutagen-producing activity from IQ in a reconstituted system. Together with these and other results reported previously, it is concluded that at least two forms of cytochrome P-450 [P-450-HM4 and P-450PA (human P-450IA2)] are involved in the mutagenic activation of IQ in human liver.
authors.affiliation: Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Ubukata
authors.forename: H
authors.initials: H
authors.lastname: Ohi
authors.forename: M
authors.initials: M
authors.lastname: Kitada
authors.forename: T
authors.initials: T
authors.lastname: Kamataki
mesh_terms: D000906:Antibodies; D001711:Biotransformation; D015153:Blotting, Western; D002852:Chromatography, Ion Exchange; D003577:Cytochrome P-450 Enzyme System / Q000302:isolation & purification / Q000378:metabolism*; D006801:Humans; D007527:Isoenzymes / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D008862:Microsomes, Liver / Q000201:enzymology*; D009153:Mutagens / Q000378:metabolism*; D011804:Quinolines / Q000378:metabolism*
chemical_list: D000906:Antibodies; D007527:Isoenzymes; D009153:Mutagens; D011804:Quinolines; C029216:2-amino-3-methylimidazo(4,5-f)quinoline; D003577:Cytochrome P-450 Enzyme System