[2][3] Alternative names: Glucuronosyltransferases are responsible for the process of glucuronidation, a major part of phase II metabolism.

Arguably the most important of the Phase II (conjugative) enzymes, UGTs have been the subject of increasing scientific inquiry since the mid-to-late 1990s.

The reaction catalyzed by the UGT enzyme involves the addition of a glucuronic acid moiety to xenobiotics and is the most important pathway for the human body's elimination of the most frequently prescribed drugs.

Famously, UGT enzymes are not present in the genus Felis,[4] and this accounts for a number of unusual toxicities in the cat family.

Infants may have a developmental deficiency in UDP-glucuronyl transferase, and are unable to hepatically metabolize the antibiotic drug chloramphenicol which requires glucuronidation.