UGT1A10 is a UDP-glucuronosyltransferase expressed primarily in gastrointestinal tissues that catalyzes glucuronidation of diverse xenobiotics and endogenous compounds. Despite UniProt annotations suggesting it lacks glucuronidation activity, multiple studies demonstrate robust enzymatic function. UGT1A10 exhibits high catalytic activity toward the anticancer drug SN-38 (active metabolite of irinotecan), with upregulation contributing to chemotherapy resistance in lung cancer 1. The enzyme displays exceptionally high activity for troglitazone glucuronidation in intestinal microsomes, with kinetic parameters (Km 11.1 μM, Vmax 33.6 pmol/min/mg) superior to hepatic UGT1A1, and intestinal glucuronidation capacity exceeds liver 3-fold 2. UGT1A10 is the dominant enzyme for estrone glucuronidation and catalyzes 16α-hydroxyestrone conjugation, indicating significant roles in estrogen metabolism 3. The enzyme primarily localizes to small intestinal epithelial cells of crypts and villi with 16-fold interindividual protein variability 4. While traditionally considered extrahepatic, UGT1A10 mRNA is upregulated in primary hepatocytes following xenobiotic induction 5. UGT1A10 contributes to metabolism of dietary polyphenols including piceatannol 6, and serves as a prognostic marker in hepatocellular carcinoma models 7. These findings establish UGT1A10 as a functionally important Phase II metabolizing enzyme with clinical relevance in drug metabolism and cancer biology.