Phase II detoxifying enzyme

Phase II detoxifying enzymes are a broad group of conjugating transferases that play a central role in the body’s detoxification system. They act primarily in the liver but are also found in other tissues. Their main function is to attach endogenous hydrophilic groups—such as glucuronic acid (via UDP-glucuronosyltransferases), sulfate (via sulfotransferases), acetyl groups (via N-acetyltransferases), methyl groups (via methyltransferases), glutathione (via glutathione S-transferases)—to potentially harmful substances that have been activated by phase I metabolism. This process transforms lipophilic toxins into more water-soluble forms that can be safely excreted via urine or bile. These reactions not only facilitate elimination but also generally reduce the biological activity and toxicity of their substrates. The term "Phase II detoxifying enzymes pathway" does not refer to a single molecule or receptor but rather an entire class/family of enzymatic processes involved in biotransformation. Therefore it is not considered a therapeutic target itself; instead individual members within this family—such as UDP-glucuronosyltransferase 1A1—may be considered targets for research or intervention depending on context. Impairments due to genetic variation can result in reduced capacity for detoxification leading to increased susceptibility to adverse effects from drugs and environmental toxins; conversely some cancers may exploit altered expression levels for survival advantage.

Other names

Phase II drug-metabolizing enzymePhase II conjugation enzymeConjugation enzymeDetoxification phase II enzymes

Conjugation with endogenous molecules such as glucuronic acid, sulfate, glycine, glutathione to increase water solubility and promote excretion