Glucuronidation

A conjugation reaction catalysed by a glucuronosyl transferase enzyme wherein a sugar (glucuronic acid) molecule is attached to a drug or to a phase I metabolite to render the conjugate more water-soluble and easier to eliminate in the urine or faeces.

Conjugates larger than around 400 g/mol are often eliminated in the faeces via the bile. Once in the intestine, they may undergo enterohepatic recirculation, a result of bacterial enzymes in the gut that cleave the sugar from the conjugate to leave the parent drug or phase I metabolite. This species can then be reabsorbed from the GI tract and after passing through the liver, can again distribute to tissues to extend the life of the therapeutic agent.