Cytochrome P450 3A4 and Cytochrome P450 2E1 (CYP3A4, CYP2E1)

Cytochrome P450 3A4 (CYP3A4) and Cytochrome P450 2E1 (CYP2E1) are members of the cytochrome P450 superfamily of heme-containing monooxygenases, predominantly expressed in the liver but also present in other tissues. CYP3A4 is responsible for the metabolism of over 50% of all clinically used drugs—making it the most important isoenzyme for drug interactions—while CYP2E1 specializes in metabolizing small, polar molecules such as ethanol and is involved in the activation of certain environmental toxins and carcinogens. Both enzymes participate in essential physiological and pharmacological processes, including the detoxification and bioactivation of endogenous and exogenous compounds. They play significant roles in clinical drug-drug interactions, pharmacogenomics, and susceptibility to toxicity or disease due to their influence on drug elimination and endogenous substrate metabolism.

Other names

CYP3A4: Cytochrome P450 family 3 subfamily A member 4CYP2E1: Cytochrome P450 family 2 subfamily E member 1Microsomal ethanol-oxidizing systemP450 enzymes (superfamily)

Oxidative metabolism via heme-dependent monooxygenation of substrates (RH + O₂ + NADPH + H⁺ → ROH + H₂O + NADP⁺) Conversion of prodrugs to active forms (activation) Bioactivation of toxic compounds (e.g., conversion of acetaminophen to hepatotoxic metabolites by CYP2E1) Detoxification and clearance of xenobiotics