TY - JOUR T1 - Functional Characterization of 21 Allelic Variants of Dihydropyrimidine Dehydrogenase Identified in 1070 Japanese Individuals JF - Drug Metabolism and Disposition JO - Drug Metab Dispos SP - 1083 LP - 1090 DO - 10.1124/dmd.118.081737 VL - 46 IS - 8 AU - Eiji Hishinuma AU - Yoko Narita AU - Sakae Saito AU - Masamitsu Maekawa AU - Fumika Akai AU - Yuya Nakanishi AU - Jun Yasuda AU - Masao Nagasaki AU - Masayuki Yamamoto AU - Hiroaki Yamaguchi AU - Nariyasu Mano AU - Noriyasu Hirasawa AU - Masahiro Hiratsuka Y1 - 2018/08/01 UR - http://dmd.aspetjournals.org/content/46/8/1083.abstract N2 - Dihydropyrimidine dehydrogenase (DPD, EC 1.3.1.2), encoded by the DPYD gene, is the rate-limiting enzyme in the degradation pathway of endogenous pyrimidine and fluoropyrimidine drugs such as 5-fluorouracil (5-FU). DPD catalyzes the reduction of uracil, thymine, and 5-FU. In Caucasians, DPYD mutations, including DPYD*2A, DPYD*13, c.2846A>T, and c.1129-5923C>G/hapB3, are known to contribute to interindividual variations in the toxicity of 5-FU; however, none of these DPYD polymorphisms has been identified in the Asian population. Recently, 21 DPYD allelic variants, including some novel single-nucleotide variants (SNVs), were identified in 1070 healthy Japanese individuals by analyzing their whole-genome sequences (WGSs), but the functional alterations caused by these variants remain unknown. In this study, in vitro analysis was performed on 22 DPD allelic variants by transiently expressing wild-type DPD and 21 DPD variants in 293FT cells and characterizing their enzymatic activities using 5-FU as a substrate. DPD expression levels and dimeric forms were determined using immunoblotting and blue-native PAGE, respectively. Additionally, the values of three kinetic parameters—the Michaelis constant (Km), maximum velocity (Vmax), and intrinsic clearance (CLint = Vmax/Km)—were determined for the reduction of 5-FU. Eleven variants exhibited significantly decreased intrinsic clearance compared with wild-type DPD. Moreover, the band patterns observed in the immunoblots of blue-native gels indicated that DPD dimerization is required for enzymatic activity in DPD. Thus, the detection of rare DPYD variants might facilitate severe adverse effect prediction of 5-FU–based chemotherapy in the Japanese population. ER -