UGT3A1 (UDP glycosyltransferase 3 family, polypeptide A1) is a 523 amino acid single-pass type I membrane protein that belongs to the UDP-glycosyltransferase family. It has been suggested that members of the UGT3A family may have an important role in the metabolism and elimination of ursodeoxycholic acid, a metabolic byproduct of intestinal bacteria. UDP-glucuronosyltransferases catalyze phase II biotransformation reactions in which lipophilic substrates are conjugated with glucuronic acid to increase water solubility and enhance excretion. They are of major importance in the conjugation and subsequent elimination of potentially toxic xenobiotics and endogenous compounds (By similarity).