Major Hepatic Cytochrome P450 Enzymes (CYP1A2, CYP2C9, CYP2D6, CYP3A4) (CYPs)

This entry represents the four most pharmacologically significant members of the human Cytochrome P450 (CYP) superfamily: CYP1A2, CYP2C9, CYP2D6, and CYP3A4. These heme-containing enzymes are primarily located in the liver and intestinal mucosa, where they catalyze the Phase I oxidative metabolism of approximately 80-90% of all clinically used drugs [1, 6, 13]. CYP3A4 is the most abundant isoform, responsible for metabolizing roughly half of marketed medications, while CYP2D6 and CYP2C9 exhibit high genetic polymorphism, leading to significant inter-individual variability in drug efficacy and toxicity [4, 10, 13]. While these enzymes are not typically intended therapeutic targets for treating specific diseases, they are critical considerations in drug development because their inhibition or induction by one drug can drastically alter the pharmacokinetics of co-administered medications, resulting in serious drug-drug interactions (DDIs) [5, 9, 13]. Understanding the activity and genetic status of these enzymes is fundamental to personalized medicine and the prevention of adverse drug reactions [3, 11, 12].

Other names

Cytochrome P450 1A2Cytochrome P450 2C9Cytochrome P450 2D6Cytochrome P450 3A4CYP450 enzymesHepatic microsomal enzymesPhase I metabolizing enzymes

CYP-mediated monooxygenation involving the insertion of one oxygen atom into a substrate and the reduction of the second oxygen atom to water, typically facilitating the detoxification and excretion of xenobiotics [7, 10].