RT Journal Article SR Electronic T1 A Functional Genetic Polymorphism on Human Carbonyl Reductase 1 (CBR1 V88I) Impacts on Catalytic Activity and NADPH Binding Affinity JF Drug Metabolism and Disposition JO Drug Metab Dispos FD American Society for Pharmacology and Experimental Therapeutics SP 973 OP 980 DO 10.1124/dmd.107.014779 VO 35 IS 6 A1 Vanessa Gonzalez-Covarrubias A1 Debashis Ghosh A1 Sukhwinder S. Lakhman A1 Lakshmi Pendyala A1 Javier G. Blanco YR 2007 UL http://dmd.aspetjournals.org/content/35/6/973.abstract AB Human carbonyl reductase 1 (CBR1) metabolizes endogenous and xenobiotic substrates such as the fever mediator, prostaglandin E2 (PGE2), and the anticancer anthracycline drug, daunorubicin. We screened 33 CBR1 full-length cDNA samples from white and black liver donors and performed database analyses to identify genetic determinants of CBR1 activity. We pinpointed a single nucleotide polymorphism on CBR1 (CBR1 V88I) that encodes for a valine-to-isoleucine substitution for further characterization. We detected the CBR1 V88I polymorphism in DNA samples from individuals with African ancestry (p = 0.986, q = 0.014). Kinetic studies revealed that the CBR1 V88 and CBR1 I88 isoforms have different maximal velocities for daunorubicin (Vmax CBR1 V88, 181 ± 13 versus Vmax CBR1 I88, 121 ± 12 nmol/min · mg, p < 0.05) and PGE2 (Vmax CBR1 V88, 53 ± 7 versus Vmax CBR1 I88, 35 ± 4 nmol/min · mg, p < 0.01). Concomitantly, CBR1 V88 produced higher levels of the cardiotoxic metabolite daunorubicinol compared with CBR1 I88 (1.7-fold, p < 0.0001). Inhibition studies demonstrated that CBR1 V88 and CBR1 I88 are distinctively inhibited by the flavonoid, rutin (IC50 CBR1 V88, 54.0 ± 0.4 μM versus IC50 CBR1 I88, 15.0 ± 0.1 μM, p < 0.001). Furthermore, isothermal titration calorimetry analyses together with molecular modeling studies showed that CBR1 V88I results in CBR1 isoforms with different binding affinities for the cofactor NADPH (Kd CBR1 V88, 6.3 ± 0.6 μM versus Kd CBR1 I88, 3.8 ± 0.5 μM). These studies characterize the first functional genetic determinant of CBR1 activity toward relevant physiological and pharmacological substrates. The American Society for Pharmacology and Experimental Therapeutics