Genetic polymorphism of UDP-glucuronosyltransferase 2B7 (UGT2B7) at amino acid 268: ethnic diversity of alleles and potential clinical significance

UGT2B7 catalyses the glucuronidation of a diverse range of drugs, environme ntal chemicals and endogenous compounds. Hence, coding region polymorphisms of UGT2B7 are potentially of pharmacological, toxicological and physiologi cal significance. Two variant UGT2B7 cDNAs encoding enzymes with either His or Tyr at residue 268 have been isolated, The variants, referred to as UGT 2B7*1 and UGT2B7*2, respectively, arise from a C to T transversion at nucle otide 802 of the UGT2B7 coding region. Analysis of genomic DNA from 91 unre lated Caucasians and 84 unrelated Japanese demonstrated the presence of the variant alleles encoding UGT2B7*1 and UGT2B7*2 in both populations. Howeve r, while there was an approximately equal distribution of subjects homozygo us for each allele in the Caucasian population, subjects homozygous for the UGT2B7*1 allele were over 10-fold more prevalent than UGT2B7*2 homozygotes in Japanese, The frequencies of the UGT2B7*1 and UGT2B7*2 alleles were 0.5 11 and 0.489, respectively, in Caucasians, and 0.732 and 0.268, respectivel y, in Japanese. The 95% confidence intervals for the two alleles did not ov erlap between Caucasians and Japanese. Rates of microsomal androsterone, me nthol and morphine (3-position) glucuronidation were determined for genotyp ed livers from Caucasian donors. Statistically significant inter-genotypic differences were not apparent for any of the three substrates. Although the UGT2B7 polymorphism characterized here is probably not associated with alt ered enzyme activity, the results highlight the need to consider ethnic var iability in assessing the consequences of UGT polymorphisms, Pharmacogeneti cs 10:679-685 (C) 2000 Lippincott Williams & Wilkins.