Cytochrome P450 1A2 (CYP1A2) [T88.7]
OMIM number: 124060 (CYP1A2)
Dipl.-Biol. Birgit Busse
The enzyme CYP3A5 is one of the rare isoforms of the CYP3A group and is only expressed in a minority of the population. Up to 90% of Caucasians have a non-expressor phenotype and very low CYP3A5 enzyme activity due to a polymorphism in the gene (CYP3A5*3 allele). People with at least one CYP3A5*1 allele have increased enzyme expression (expressors). In carriers of this allele CYP3A5 accounts for up to 50% of the hepatic CYP3A portion, whereby the metabolism of CYP3A substrates is accelerated. Patients with the CYP3A5*1 genotype respond to CYP3A5 dependent medication worse than patients with the CYP3A5*3 /*3 genotype. CYP3A5 is involved in the metabolism and synthesis of cholesterol, steroid hormones (testosterone, progesterone, androstenedione) and other lipids, and also in the degradation of a number of drugs (e.g., cyclosporine, various statins, psychotropic drugs and chemotherapeutic agents).