ORIGINAL ARTICLESDiscovery of new potentially defective alleles of human CYP2C9Blaisdell, Joycea; Jorge-Nebert, Lucia Fb; Coulter, Sherrya; Ferguson, Stephen Sa; Lee, Su-Juna; Chanas, Briana; Xi, Tinac; Mohrenweiser, Harveyc; Ghanayem, Burhana; Goldstein, Joyce AaAuthor Information aLaboratory of Pharmacology and Chemistry, Human Metabolism Section, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA, bDNA and Human Genomics Institute and College of Pharmacy, University of Panama, Panama, Republic of Panama and cLawrence Livermore National Laboratory, Livermore, California, USA. Sponsorship: Work at Lawrence Livermore National Laboratory was performed under the auspices of the US Department of Energy by Lawrence Livermore National Laboratory contract No. W-7405-ENG-48 and supported by interagency agreement Y1. Correspondence and requests for reprints to Dr Joyce Goldstein, Laboratory of Pharmacology and Chemistry, Human Metabolism Section, National Institute of Environmental Health Sciences, PO Box 12233, Research Triangle Park, NC 27709, USA. Tel: +1 919 541 4495; fax: +1 919 541 4107; e-mail: [email protected] Received 5 December 2003 Accepted 30 April 2004 Pharmacogenetics: August 2004 - Volume 14 - Issue 8 - p 527-537 doi: 10.1097/01.fpc.0000114759.08559.51 Buy Metrics Abstract CYP2C9 is a clinically important enzyme, responsible for the metabolism of numerous clinically important therapeutic drugs. In the present study, we discovered 38 single nucleotide polymorphisms in CYP2C9 by resequencing of genomic DNA from 92 individuals from three different racial groups. Haplotype analysis predicted that there are at least 21 alleles of CYP2C9 in this group of individuals. Six new alleles were identified that contained coding changes: L19I (CYP2C9*7), R150H (CYP2C9*8), H251R (CYP2C9*9), E272G (CYP2C9*10), R335W(CYP2C9*11) and P489S (CYP2C9*12). When expressed in a bacterial cDNA expression system, several alleles exhibited altered catalytic activity. CYP2C9*11 appeared to be a putative poor metabolizer allele, exhibiting a three-fold increase in the Km and more than a two-fold decrease in the intrinsic clearance for tolbutamide. Examination of the crystal structure of human CYP2C9 reveals that R335 is located in the turn between the J and J′ helices and forms a hydrogen-bonding ion pair with D341 from the J′ helix. Abolishing this interaction in CYP2C9*11 individuals could destabilize the secondary structure and alter the substrate affinity. This new putative poor metabolizer (PM) allele was found in Africans. A second potentially PM allele CYP2C9*12 found in a racially unidentified sample also exhibited a modest decrease in the Vmax and the intrinsic clearance for tolbutamide in a recombinant system. Further clinical studies are needed to determine the effect of these new polymorphisms on the metabolism of CYP2C9 substrates. © 2004 Lippincott Williams & Wilkins, Inc.