UDP-glucuronosyltransferase (UGT) that catalyzes phase II biotransformation reactions in which lipophilic substrates are conjugated with glucuronic acid to increase the metabolite's water solubility, thereby facilitating excretion into either the urine or bile (PubMed:12181437, PubMed:18004212, PubMed:18052087, PubMed:18674515, PubMed:18719240, PubMed:19545173, PubMed:23288867, PubMed:26220143). Essential for the elimination and detoxification of drugs, xenobiotics and endogenous compounds (PubMed:12181437, PubMed:18004212). Catalyzes the glucuronidation of endogenous estrogen hormones such as estradiol, estrone and estriol (PubMed:18719240, PubMed:23288867, PubMed:26220143). Also catalyzes the glucuronidation of the isoflavones genistein, daidzein, glycitein, formononetin, biochanin A and prunetin, which are phytoestrogens with anticancer and cardiovascular properties (PubMed:18052087, PubMed:19545173). Involved in the glucuronidation of the AGTR1 angiotensin receptor antagonist losartan, caderastan and zolarsatan, drugs which can inhibit the effect of angiotensin II (PubMed:18674515). Lacks UGT glucuronidation activity but acts as a negative regulator of isoform 1. glucuronate acceptor + UDP-alpha-D-glucuronate = acceptor beta-D-glucuronoside + H(+) + UDP 17beta-estradiol + UDP-alpha-D-glucuronate = 17beta-estradiol 3-O-(beta-D-glucuronate) + H(+) + UDP 17beta-estradiol + UDP-alpha-D-glucuronate = 17beta-estradiol 17-O-(beta-D-glucuronate) + H(+) + UDP 17alpha-estradiol + UDP-alpha-D-glucuronate = 17alpha-estradiol 3-O-(beta-D-glucuronate) + H(+) + UDP 16alpha,17beta-estriol + UDP-alpha-D-glucuronate = 16alpha,17beta-estriol 3-O-(beta-D-glucuronate) + H(+) + UDP 16beta,17beta-estriol + UDP-alpha-D-glucuronate = 16beta,17beta-estriol 3-O-(beta-D-glucuronate) + H(+) + UDP 16alpha,17alpha-estriol + UDP-alpha-D-glucuronate = 16alpha,17alpha-estriol 3-O-(beta-D-glucuronate) + H(+) + UDP 16alpha-hydroxyestrone + UDP-alpha-D-glucuronate = 16alpha-hydroxyestrone 3-O-(beta-D-glucuronate) + H(+) + UDP estrone + UDP-alpha-D-glucuronate = estrone 3-O-(beta-D-glucuronate) + H(+) + UDP prunetin + UDP-alpha-D-glucuronate = prunetin-4'-O-beta-D-glucuronide + UDP losartan + UDP-alpha-D-glucuronate = losartan-2-N-beta-D-glucuronide + UDP candesartan + UDP-alpha-D-glucuronate = candesartan O-beta-D-glucuronoside + UDP candesartan + UDP-alpha-D-glucuronate = candesartan-2-N-beta-D-glucuronide + UDP UDP-alpha-D-glucuronate + zolasartan = UDP + zolarsartan-1-N-beta-D-glucuronide Some kinetic parameters were assessed using commercial enzymes, which may represent a mix of both active and inactive protein forms, and therefore modify the kinetic values. Homodimer (PubMed:17179145). Homooligomer (Probable). Interacts with UGT1A1, UGT1A3, UGT1A4, UGT1A6, UGT1A7, UGT1A8 and UGT1A9 to form heterodimers (PubMed:17179145). Isoform 1 interacts with isoform 2/i2 suggesting that oligomerization is involved in negative regulation of transferase activity by isoform 2. Isoform 1 also interacts with respective i2 isoforms of UGT1A1, UGT1A3, UGT1A4, UGT1A6, UGT1A7, UGT1A8 and UGT1A9 (PubMed:20610558). Liver and colon (PubMed:9271343). Isoform 1 and isoform 2 are expressed in colon, esophagus and small intestine; isoform 2 but not isoform 1 is expressed in liver or kidney (PubMed:18004212). UGT1A10 isoform is part of the UGT1A complex locus which displays alternative use of promoters, first exons and terminal exons. The locus is defined by 13 first exons, which are alternatively spliced to 3 other common exons and 2 alternative terminal exons 5. From the 27 possible mRNA isoforms, 9 produce functionally active polypeptides (UGT1A1, 1A3, 1A4, 1A5, 1A6, 1A7, 1A8, 1A9 and 1A10) called isoforms 1 (i1). Use of an alternative exon 5 (5b) as terminal exon is leading to 9 additional alternatively spliced products termed isoforms i2 and which lack transferase activity. Belongs to the UDP-glycosyltransferase family.