PT - JOURNAL ARTICLE AU - Katsunobu Hagihara AU - Miho Kazui AU - Atsushi Kurihara AU - Toshihiko Ikeda AU - Takashi Izumi TI - Glutaredoxin Is Involved in the Formation of the Pharmacologically Active Metabolite of Clopidogrel from Its GSH Conjugate AID - 10.1124/dmd.112.045914 DP - 2012 Sep 01 TA - Drug Metabolism and Disposition PG - 1854--1859 VI - 40 IP - 9 4099 - http://dmd.aspetjournals.org/content/40/9/1854.short 4100 - http://dmd.aspetjournals.org/content/40/9/1854.full SO - Drug Metab Dispos2012 Sep 01; 40 AB - Clopidogrel is a thienopyridine antiplatelet agent that is converted to the active metabolite, R-361015, in vivo. Clopidogrel is first oxidized to a thiolactone intermediate R-115991. R-115991 is thought to be metabolized to a GSH conjugate of R-361015 (R-361015-SG) and then is reduced to R-361015 in the presence of GSH. In this study, we investigated the enzyme-mediated formation of R-361015 from R-361015-SG in human liver microsomes and cytosols. After incubation of R-115991 in human liver microsomes, the formation of R-361015-SG, and subsequently of R-361015, was observed. The apparent formation rate of R-361015-SG was markedly decreased when human liver cytosols were added. Fitting the data to the kinetic model showed that the rate constant of R-361015-SG reduction to R-361015 in human liver microsomes was approximately 20-fold higher in the presence of human liver cytosols (6.56 min−1) than in the absence of cytosols (0.326 min−1). In addition, the formation rate of R-361015 from R-361015-SG was higher in human liver cytosols (2843 ± 1176 pmol · min−1 · mg−1) compared with in human liver microsomes (508 ± 396 pmol · min−1 · mg−1). The formation of R-361015 from R-361015-SG in human liver microsomes or cytosols was inhibited by anti-human glutaredoxin antibody in a concentration-dependent manner. Recombinant human glutaredoxin mediated the formation of R-361015 from R-361015-SG with the Km and Vmax values of 30.0 ± 1.3 μM and 381.6 ± 209.8 pmol · min−1 · μg−1, respectively. The intrinsic clearance value (Vmax/Km) was 12.9 ± 7.5 μl · min−1 · μg−1. In conclusion, we found that human glutaredoxin is a main contributor to the formation of the pharmacologically active metabolite of clopidogrel from its GSH conjugate in human liver.