What Are Phase I and Phase II Metabolic Reactions?
Phase I reactions involve the introduction or unmasking of functional groups through oxidation, reduction, or hydrolysis, primarily facilitated by the cytochrome P450 enzyme family. These reactions often result in the activation or inactivation of the toxicant.
Phase II reactions involve conjugation with endogenous substrates like glucuronic acid, sulfate, or glutathione, increasing the molecule's water solubility and promoting excretion. These reactions are catalyzed by transferase enzymes such as UDP-glucuronosyltransferase and sulfotransferase.
