Cytochrome P450 (CYP450) enzymes are a superfamily of oxidative catalysts important in the biosynthesis and metabolism of a wide range of endogenous molecules as well as the metabolism of xenobiotics. For example, CYP2B4 metabolizes substituted amines, CYP2E1 metabolizes various alcohols and halogenated alkenes, and CYP1A2 catalyzes the oxygenation of aromatic compounds and polycyclic hydrocarbons. 4-phenyl-1,2,3-Thiadiazole is, at 100 μM, a selective inhibitor of certain CYP450 enzymes (CYP2B4, CYP2E1), but not others (CYP1A2), with inactivation occurring in a mechanism-based manner. 1,2,3-Thiadiazole compounds and their derivatives, including 4-phenyl-1,2,3-thiadiazole, are also commonly used as fungicides, herbicides, and plant growth regulators.