title: CYP3A5 Contributes significantly to CYP3A-mediated drug oxidations in liver microsomes from Japanese subjects.
abstract: The purpose of this study was to evaluate a contribution of polymorphic cytochrome P450 (CYP) 3A5 to the oxidation of diltiazem, midazolam and testosterone by liver microsomes from Japanese subjects. Twenty-seven liver samples were classified into three groups according to the CYP3A5 genotypes; CYP3A5(*)1/(*)1 (n=3), (*)1/(*)3 (n=12) and (*)3/(*)3 (n=12). The results of genotyping and immunochemical quantitation of CYP3A5 protein showed a good accordance between the CYP3A5 genotype and CYP3A5 content but not CYP3A4 content in liver microsomes. The expression levels of hepatic CYP3A5 protein ranged from 20 to 60% of the sum of CYP3A4 and CYP3A5 contents in subjects with at least one wild type allele ((*)1). The CYP3A5 contents correlated well with liver microsomal activities of diltiazem N-demethylation, midazolam 1'- and 4-hydroxylations and testosterone 6beta-hydroxylation among subjects carrying at least one (*)1 allele. In addition, the correlation coefficients of CYP3A5 contents with the rates of diltiazem N-demethylation, midazolam 1'-hydroxylation and testosterone 6beta- hydroxylation were higher than those of CYP3A4, although the value of CYP3A5 with the midazolam 4-hydroxylation rate was similar to that of CYP3A4. Kinetic analyses revealed a biphasic diltiazem N-demethylation in liver microsomes from subjects carrying the (*)1 allele. The apparent V(max)/K(m) values for recombinant CYP3A5 indicated the greater contributions to diltiazem N-demethylation and midazolam 1'-hydroxylation as compared with CYP3A4. These results suggest that polymorphic CYP3A5 contributes markedly to the drug oxidations, particularly diltiazem N-demethylation, midazolam 1'- hydroxylation and testosterone 6beta-hydroxylation by liver microsomes from Japanese subjects.
authors.affiliation: Laboratory of Drug Metabolism, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo. s-yamaori@hokuriku-u.ac.jp
authors.forename: Satoshi
authors.initials: S
authors.lastname: Yamaori
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yamazaki
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Iwano
authors.forename: Kazuma
authors.initials: K
authors.lastname: Kiyotani
authors.forename: Keiko
authors.initials: K
authors.lastname: Matsumura
authors.forename: Goro
authors.initials: G
authors.lastname: Honda
authors.forename: Kazuko
authors.initials: K
authors.lastname: Nakagawa
authors.forename: Takashi
authors.initials: T
authors.lastname: Ishizaki
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Kamataki
mesh_terms: D002121:Calcium Channel Blockers / Q000378:metabolism; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics* / Q000378:metabolism*; D004247:DNA / Q000235:genetics; D017931:DNA Primers; D003640:Dealkylation; D004110:Diltiazem / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism; D018757:GABA Modulators / Q000378:metabolism; D005838:Genotype; D006801:Humans; D006900:Hydroxylation; D066298:In Vitro Techniques; D007564:Japan; D007700:Kinetics; D008862:Microsomes, Liver / Q000201:enzymology*; D008874:Midazolam / Q000378:metabolism; D009251:NADPH-Ferrihemoprotein Reductase / Q000235:genetics / Q000378:metabolism; D010084:Oxidation-Reduction; D004364:Pharmaceutical Preparations / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013739:Testosterone / Q000378:metabolism
chemical_list: D002121:Calcium Channel Blockers; D017931:DNA Primers; D018757:GABA Modulators; D004364:Pharmaceutical Preparations; D013739:Testosterone; D004247:DNA; D003577:Cytochrome P-450 Enzyme System; C104464:CYP3A protein, human; C510164:CYP3A5 protein, human; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D009251:NADPH-Ferrihemoprotein Reductase; D004110:Diltiazem; D008874:Midazolam