Glucuronosyltransferase

Overview
Uridine 5'-diphospho-glucuronosyltransferase (UDP-glucuronosyltransferase, UGT) is a glycosyltransferase that catalyzes the glucuronidation reaction.

Alternative names:
 * glucuronyltransferase

Function
This reaction involves the addition of sugars to lipids and other apolar xenobiotics and is an important step in the body's elimination of foreign substances (such as drugs and medications) as well as endogenous substances (including endogenous toxins). UGT is present in humans, other animals, plants, and bacteria.

The glucuronidation reaction consists of the transfer of the glucuronosyl group from uridine 5'-diphospho-glucuronic acid (UDPGA) to substrate molecules that contain oxygen, nitrogen, sulfur or carboxyl functional groups. The resulting glucuronide more polar (e.g. hydrophilic) and is more easily excreted than the substrate molecule. The product solubility in blood is increased allowing it to be eliminated from the body by the kidneys.

Diseases
A deficiency in the bilirubin specific form of glucuronosyltransferase is thought to be the cause of Gilbert's syndrome, which is characterized by hyperbilirubinemia.

It is also associated with Crigler-Najjar syndrome, a more serious disorder where the enzyme's activity is either completely absent (Crigler-Najjar syndrome type I) or less than 10% of normal (type II).

Genes