The function of Ensembl gene identifier ENSG00000145626 (UGT3A1, UDP glycosyltransferase family 3 member A1) is as follows. Involved in biotransformation reactions in which lipophilic substrates are conjugated with sugars to increase water solubility and enhance excretion. Such reactions are of major importance in the elimination of potentially toxic xenobiotics and endogenous compounds. It catalyzes the transfer of N-acetylglucosamine from UDP-N- acetylglucosamine to the bile acid ursodeoxycholic acid (UDCA) (PubMed:18981171). UDP-N-acetylglucosamine is the preferred sugar donor, while the enzyme has low activity with UDP-glucose and UDP- galactose (PubMed:18981171, PubMed:22621930). Is inactive with UDP- xylose and UDP-glucuronic acid as sugar donors (PubMed:18981171). In addition to UDCA, it can use, to a lesser extent, 17alpha-estradiol, 17beta-estradiol, 4-nitrophenol and 1-naphtol as sugar acceptors (PubMed:18981171). Has very low activity with 4-methylumbelliferone and genistein as sugar acceptors, and has negligible activity, if any, toward cholic acid, chenodeoxycholic acid, deoxycholic acid, lithocholic acid, and hyodeoxycholic acid (PubMed:18981171, PubMed:22621930). {ECO:0000269|PubMed:18981171, ECO:0000269|PubMed:22621930}.