[Cytochrome p450 and their implication in chemotherapy]

The hepatic cytochrome P450 enzymes (CYP450) play a prominent part in the metabolism of drugs, toxicants and some endogenous compounds. After a brief recall of their biochemical properties, the recent nomenclature is proposed. They are members of a large superfamily with various functions; the specialization of 3 families, CYP1, CYP2, CYP3 towards the metabolism of foreign and artificial compounds gives way to some evolutive considerations. Three main features are characteristic: these enzymes are poorly selective as a matter of substrates; some display genetic polymorphism; some are highly inducible. The mechanism of induction is detailed for CYP1A1. The consequences in pharmacotherapy are deduced: the CYP450 are the main cause of the variability in pharmacokinetics, of drug interactions and of drug adverse events of type II. Their implication in carcinogenesis, although controversial, deserves attention and requires further studies.