Cytochrome P450 1A2 (CYP1A2), Cytochrome P450 2C19 (CYP2C19), Cytochrome P450 2C9 (CYP2C9), and Cytochrome P450 3A4 (CYP3A4) (CYP1A2, CYP2C19, CYP2C9, CYP3A4)

Cytochrome P450 (CYP) enzymes, specifically the 1A2, 2C9, 2C19, and 3A4 isoforms, are a superfamily of heme-containing monooxygenases primarily located in the liver's endoplasmic reticulum. They play a critical role in the Phase I metabolism of approximately 70-80% of clinical drugs, as well as endogenous compounds like steroids and fatty acids [1]. CYP3A4 is the most abundant and versatile isoform, responsible for metabolizing nearly half of all marketed drugs [2]. CYP2C9 and CYP2C19 are highly polymorphic, leading to significant inter-individual variability in drug response, such as with the anticoagulant warfarin or the antiplatelet clopidogrel [3]. CYP1A2 is involved in the metabolism of caffeine and theophylline and is notably induced by tobacco smoke [4]. While these enzymes are rarely the primary therapeutic targets of drugs, they are central to pharmacokinetics, determining drug clearance and the risk of drug-drug interactions [5]. Consequently, they are a major focus in drug development and clinical safety assessments to prevent adverse reactions [6].

Other names

CYPP450Microsomal monooxygenaseHeme-thiolate proteinDrug-metabolizing enzymes

These enzymes catalyze the Phase I oxidative metabolism of drugs and endogenous compounds by inserting one atom of molecular oxygen into the substrate while reducing the other to water, a process requiring NADPH and cytochrome P450 reductase [1, 5].