Glucuronidation

Illustration of glucuronidation of biphenyl amine.

Glucuronidation is a biochemical process that involves the addition of glucuronic acid to substances, facilitating their excretion from the body. This process is a major pathway of phase II metabolism in the liver, where it plays a crucial role in the detoxification and elimination of both endogenous and exogenous compounds.

Mechanism

Glucuronidation is catalyzed by the family of enzymes known as UDP-glucuronosyltransferases (UGTs). These enzymes transfer glucuronic acid from the cofactor uridine diphosphate glucuronic acid (UDPGA) to a substrate, which can be a drug, hormone, or toxin. The resulting glucuronide conjugates are more water-soluble, allowing for easier excretion via the urinary system or bile.

Substrates

A wide variety of substrates undergo glucuronidation, including:

• Bilirubin
• Steroid hormones
• Thyroid hormones
• Drugs such as acetaminophen, morphine, and ibuprofen
• Environmental toxins

Clinical Significance

Glucuronidation is essential for the metabolism and clearance of many therapeutic drugs. Impairments in this pathway can lead to drug toxicity or ineffective drug therapy. Genetic polymorphisms in UGT enzymes can affect an individual's ability to metabolize certain drugs, influencing drug efficacy and safety.

Related Enzymes

The UGT enzyme family is divided into several subfamilies, including UGT1A and UGT2B, each with specific substrate affinities. These enzymes are primarily located in the liver, but are also found in other tissues such as the intestine, kidney, and brain.

Related Pages

• Phase I metabolism
• Cytochrome P450
• Conjugation reactions
• Drug metabolism