UDP-Glucuronosy transferases

The uridine diphosphate (UDP)-glycosyltransferases are a group of enzymes that catalyze the transfer of sugars to a variety of acceptor molecules. When the enzymes catalyze this reaction, they are also referred to as UDP-glucuronosyltransferases (UGTs). This chapter reviews the role of these enzymes in drug-drug interactions that occur in humans. The UGT1A enzymes are generally named in order of their proximity to the four constant region exons, i.e., UGT1A1 through UGT1A13. The arrangement appears to be conserved across all mammalian species studied to date. In humans, all of the gene products are functions except for pseudogenes UGT1A2, UGT1A11, UGT1A12, and UGT1A13. UGTs are membrane-bound enzymes located intracellularly in the endoplasmic reticulum. Glucuronides can also be substrates for cytochrome P450 enzymes. Gemfibrozil glucuronide was shown to be a potent inhibitor of CYP2C8, and inhibition of CYP2C8 and competition of the UGT-catalyzed lactonization of statins is the mechanism for the interaction between cerivastatin and gemfibrozil.