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UGT1A3
UGT1A3 Full Name
UDP glucuronosyltransferase 1 family, polypeptide A3
UGT1A3 Introduction
UGT1A3 encodes a UDP-glucuronosyltransferase belonging to the human UGT1A family of phase II metabolizing enzymes. Like other family members, it catalyzes the conjugation of glucuronic acid from UDP-glucuronic acid to acceptor substrates, generating polar glucuronides that facilitate elimination through bile or urine. The enzyme is produced from the same complex UGT1 locus on chromosome 2 by alternative promoter usage and exon splicing, which yields multiple isoforms sharing identical C-terminal regions but differing in their N-terminal substrate-binding domains. UGT1A3 is expressed in several tissues, with notable activity in the liver, and it participates in the disposition of endogenous steroids, bile acids, and various xenobiotics. Genetic polymorphisms in UGT1A3 further modulate its activity, contributing to variability in how individuals process hormones and medications. Its broad yet selective specificity makes it one of the more functionally versatile members of the UGT1A subfamily.
Figure 1. Two major bile acid biosynthetic pathways. (Source: Gallucci GM, et al. 2024)
The substrate profile of UGT1A3 spans several physiologically important classes. It glucuronidates bile acids at their carboxyl moiety, contributing to the detoxification of these potent endogenous detergents and protecting the liver from their toxic accumulation, and it conjugates primary bile acids such as chenodeoxycholic acid in hepatic tissue. UGT1A3 also metabolizes endogenous estrogen hormones including estradiol and estrone, and it handles calcidiol, the major circulating form of vitamin D3, supporting the regulation of calcium and phosphate homeostasis. In addition, the enzyme glucuronidates certain pharmaceuticals, including the angiotensin receptor antagonist losartan, as well as dietary phytochemicals such as ferulic acid. Because bile acid and steroid conjugation are tightly coupled to metabolic health, alterations in UGT1A3 function can influence susceptibility to cholestatic and endocrine-related conditions. Together, these activities position UGT1A3 as a key conjugating enzyme linking steroid, bile acid, vitamin D, and drug metabolism, with direct relevance to hepatobiliary detoxification and interindividual variation in therapeutic response.
Alternate Names for UGT1A3
UGT1A3; UDP glucuronosyltransferase 1 family, polypeptide A3; UDPGT; UGT1C; UGT-1C; UGT1.3; UGT1-03; UDPGT 1-3; UDP-glucuronosyltransferase 1-3; UGT1*3; UDP-glucuronosyltransferase 1-C; UDP-glucuronosyltransferase 1A3; UDP glycosyltransferase 1 family, polypeptide A3;
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