title: Human CYP2C-mediated stereoselective phenytoin hydroxylation in Japanese: difference in chiral preference of CYP2C9 and CYP2C19.
abstract: Regio- and stereoselective hydroxylation of phenytoin was determined in liver microsomes of nine extensive (EM) and three poor metabolizers (PM) of mephenytoin. Hydroxyphenytoins (HPPH) were isolated and quantified after separation into four regio- and stereoisomers. The total rates of microsomal phenytoin 4'- hydroxylation were approximately 3-fold higher than those of 3'-hydroxylation, and not significantly different in EM and PM. Formation of 4'-(R)-HPPH was 4.4-fold higher in EM than in PM, whereas no clear differences between EM and PM were detected in the formation of 4'-(S)-, 3'-(R)-, and 3'-(S)-HPPH. Cytochrome P450 (CYP)2C9, expressed in a fission yeast, Schizosaccharomyces pombe, catalyzed the formation of 4'-(R)- and 4'-(S)-HPPH stereoselectively, as observed with EM, in which predominantly 4'-(S)-HPPH was formed. Recombinant CYP2C19 was more stereoselective for 4'-(R)-HPPH formation. These results, in addition to inhibition experiments with anti-human CYP2C antibody, indicate that phenytoin hydroxylation is mainly catalyzed by CYP2C9. Furthermore, CYP2C19 showed limited contribution to phenytoin 4'-hydroxylation with a different chiral preference from CYP2C9.
authors.affiliation: Department of Pharmacology, School of Medicine, Keio University, Tokyo, Japan. yasmrits@banyu.co.jp
authors.forename: T
authors.initials: T
authors.lastname: Yasumori
authors.forename: L S
authors.initials: LS
authors.lastname: Chen
authors.forename: Q H
authors.initials: QH
authors.lastname: Li
authors.forename: M
authors.initials: M
authors.lastname: Ueda
authors.forename: T
authors.initials: T
authors.lastname: Tsuzuki
authors.forename: J A
authors.initials: JA
authors.lastname: Goldstein
authors.forename: R
authors.initials: R
authors.lastname: Kato
authors.forename: Y
authors.initials: Y
authors.lastname: Yamazoe
mesh_terms: D000906:Antibodies / Q000276:immunology; D000927:Anticonvulsants / Q000378:metabolism; D001189:Aryl Hydrocarbon Hydroxylases; D002478:Cells, Cultured; D065731:Cytochrome P-450 CYP2C19; D065729:Cytochrome P-450 CYP2C9; D003577:Cytochrome P-450 Enzyme System / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D006900:Hydroxylation; D007564:Japan; D007700:Kinetics; D008862:Microsomes, Liver / Q000378:metabolism*; D006899:Mixed Function Oxygenases / Q000276:immunology / Q000378:metabolism*; D010672:Phenytoin / Q000031:analogs & derivatives / Q000378:metabolism*; D012441:Saccharomyces cerevisiae; D013237:Stereoisomerism; D039181:Steroid 16-alpha-Hydroxylase; D013250:Steroid Hydroxylases / Q000276:immunology / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D000906:Antibodies; D000927:Anticonvulsants; C001419:hydroxyphenytoin; D010672:Phenytoin; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D013250:Steroid Hydroxylases; C450260:CYP2C9 protein, human; D065729:Cytochrome P-450 CYP2C9; D001189:Aryl Hydrocarbon Hydroxylases; C045793:CYP2C19 protein, human; D065731:Cytochrome P-450 CYP2C19; D039181:Steroid 16-alpha-Hydroxylase