title: Catalytic roles of CYP2C9 and its variants (CYP2C9*2 and CYP2C9*3) in lornoxicam 5'-hydroxylation.
abstract: The effects of allelic variants of CYP2C9 (CYP2C9*2 and CYP2C9*3) on lornoxicam 5'-hydroxylation were studied using the corresponding variant protein expressed in baculovirus-infected insect cells and human liver microsomes of known genotypes of CYP2C9. The results of the baculovirus expression system showed that CYP2C9.3 gives higher K(m) and lower V(max) values for lornoxicam 5'-hydroxylation than does CYP2C9.1. In contrast, K(m) and V(max) values of CYP2C9.1 and CYP2C9.2 for the reaction were comparable. Lornoxicam 5'-hydroxylation was also determined in liver microsomes of 12 humans genotyped for the CYP2C9 gene (*1/*1, n = 7; *1/*2, n = 2; *1/*3, n = 2; *3/*3, n = 1). A sample genotyped as *3/*3 exhibited 8- to 50-fold lower intrinsic clearance for lornoxicam 5'-hydroxylation than did samples genotyped as *1/*1. However, the values for intrinsic clearance for *1/*3 were within the range of values exhibited by samples of *1/*1. In addition, no appreciable differences were observed in kinetic parameters for lornoxicam 5'-hydroxylation between *1/*1 and *1/*2. In conclusion, this study showed that lornoxicam 5'-hydroxylation via CYP2C9 was markedly decreased by the substitution of Ile359Leu (CYP2C9.3), whereas the effect of the substitution of Arg144Cys (CYP2C9.2) was nonexistent or negligible. Additional in vivo studies are required to confirm that individuals with homologous CYP2C9*3 allele exhibit impaired lornoxicam clearance.
authors.affiliation: Department of Drug Metabolism, Research Center, Taisho Pharmaceutical Co., Ltd., 403, Yoshino-cho 1-chome, Saitama-shi, Saitama 330-8530, Japan. Izumi.Iida@po.rd.taisho.co.jp
authors.forename: Izumi
authors.initials: I
authors.lastname: Iida
authors.forename: Atsunori
authors.initials: A
authors.lastname: Miyata
authors.forename: Masayuki
authors.initials: M
authors.lastname: Arai
authors.forename: Mitsuyo
authors.initials: M
authors.lastname: Hirota
authors.forename: Masayuki
authors.initials: M
authors.lastname: Akimoto
authors.forename: Shohei
authors.initials: S
authors.lastname: Higuchi
authors.forename: Kaoru
authors.initials: K
authors.lastname: Kobayashi
authors.forename: Kan
authors.initials: K
authors.lastname: Chiba
mesh_terms: D000483:Alleles; D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000378:metabolism*; D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics / Q000378:metabolism*; D016367:Baculoviridae / Q000201:enzymology / Q000235:genetics; D002384:Catalysis; D065729:Cytochrome P-450 CYP2C9; D005838:Genotype; D006801:Humans; D006900:Hydroxylation; D066298:In Vitro Techniques; D007313:Insecta / Q000378:metabolism; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D008862:Microsomes, Liver / Q000201:enzymology; D010894:Piroxicam / Q000031:analogs & derivatives* / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D007527:Isoenzymes; D011994:Recombinant Proteins; D010894:Piroxicam; C450260:CYP2C9 protein, human; D065729:Cytochrome P-450 CYP2C9; D001189:Aryl Hydrocarbon Hydroxylases; C059451:lornoxicam