Methodology to assay CYP2E1 mixed function oxidase catalytic activity and its induction

The cytochrome P450 mixed function oxidase enzymes are the major catalysts involved in drug metabolism. There are many forms of P450. CYP2E1 metabolizes many toxicologically important compounds including ethanol and is active in generating reactive oxygen species. Since several of the contributions in the common theme series "Role of CYP2E1 and Oxidative/Nitrosative Stress in the Hepatotoxic Actions of Alcohol" discuss CYP2E1, this methodology review describes assays on how CYP2E1 catalytic activity and its induction by ethanol and other inducers can be measured using substrate probes such as the oxidation of para-nitrophenol to para-nitrocatechol and the oxidation of ethanol to acetaldehyde. Approaches to validate that a particular reaction e.g. oxidation of a drug or toxin is catalyzed by CYP2E1 or that induction of that reaction is due to induction of CYP2E1 are important and specific examples using inhibitors of CYP2E1, anti-CYP2E1 IgG or CYP2E1 knockout and knockin mice will be discussed. Cytochrome P4502E1(CYP2E1) oxidizes ethanol and activates hepatoxins and procarcinogens.CYP2E1 produces reactive oxygen species during its catalytic cycle.Methodology to assay CYP2E1 via oxidation of ethanol and p-nitrophenol is reviewed.Oxidation of these substrates is enhanced after induction of CYP2E1 by ethanol.Oxidation of these substrates is lowered by CYP2E1 inhibitors, anti-CYP2E1 IgG and in CYP2E1 knockout mice.