Cytochrome P450 2C9 (CYP2C9) and Cytochrome P450 3A4 (CYP3A4) (CYP2C9, CYP3A4)

Cytochrome P450 2C9 (CYP2C9) and Cytochrome P450 3A4 (CYP3A4) are major heme-containing monooxygenases located primarily in the endoplasmic reticulum of hepatocytes and enterocytes [1, 9, 10]. They play a central role in the Phase I metabolism of approximately 65% of all clinically used drugs, with CYP3A4 alone accounting for nearly 50% of drug biotransformation [1, 6, 9]. CYP2C9 is particularly important for the metabolism of drugs with narrow therapeutic windows, such as the anticoagulant warfarin and the anticonvulsant phenytoin [2, 3]. These enzymes facilitate the oxidation, reduction, and hydrolysis of xenobiotics, making them more polar for subsequent excretion [1, 10]. Genetic variations in the genes encoding these enzymes, such as the CYP2C9*2 and *3 alleles, significantly influence individual drug metabolism rates, leading to risks of toxicity or therapeutic failure [1, 2, 3]. Consequently, they are critical focal points in pharmacogenomics and drug-drug interaction studies during pharmaceutical development [1, 6, 8].

Other names

P450 2C9P450 3A4Cytochrome P450 family 2 subfamily C member 9Cytochrome P450 family 3 subfamily A member 4CP33CP34HLPNF-25P450PCN1

These enzymes catalyze the oxidative metabolism (Phase I) of xenobiotics and endogenous compounds through monooxygenase activity, where drugs act as substrates, competitive or non-competitive inhibitors, or transcriptional inducers [1, 10].