In Vitro Identification of UDP-Glucuronosyltransferases (UGTs) Involved in Drug Metabolism

Glucuronidation catalyzed by the UDP-glucuronosyltransferases (UGTs) is a major pathway for drug metabolism and elimination in humans. Identification of the UGTs responsible for glucuronidation of existing and novel drugs will assist in the prediction of adverse reactions resulting from drug-drug interactions or genetic polymorphism. An integrated approach is proposed for UGT reaction phenotyping using recombinant enzymes and human liver microsomes. Described methods include screening of recombinant UGTs for activity, comparative enzyme kinetic analysis, correlations with isoform-selective marker activities, and chemical inhibition. The primary focus is on identification of the well-characterized hepatic UGTs, including UGTs 1A1, 1A4, 1A6, 1A9, 2B7, and 2B15, although a similar approach potentially could be used for the study of extrahepatic tissues, such as the kidney and gastrointestinal tract.