What are the Major Classes of Detoxifying Enzymes?
Detoxifying enzymes are broadly classified into three phases:
Phase I Enzymes: This phase involves enzymes such as cytochrome P450, which introduce reactive or polar groups into xenobiotics. These modifications often prepare the substrates for Phase II reactions. Phase II Enzymes: These enzymes perform conjugation reactions, where substrates are linked with an endogenous substance like glucuronic acid, sulfate, or glutathione, making them more water-soluble. Key enzymes in this phase include glutathione S-transferase and UDP-glucuronosyltransferase. Phase III Enzymes: These are transporters such as ATP-binding cassette transporters that facilitate the excretion of the conjugated compounds out of the cells.
