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cytochrome P450 family 1, subfamily A Cytochrome P450 family 1, subfamily A (CYP1A) consists of two human members, CYP1A1 and CYP1A2, which overlap in their activities. CYP1A2 is the highly expressed cytochrome enzyme in the human liver, while CYP1A1 is mostly found in extrahepatic tissues. Known common substrates include aromatic compounds such as polycyclic aromatic hydrocarbons, arachidonic acid and eicosapentoic acid, as well as melatonin and 6-hydroxylate melatonin. In addition, CYP1A1 activates procarcinogens into carcinogens via epoxides, and metabolizes heterocyclic aromatic amines of industrial origin. CYP1A2 metabolizes numerous natural products that result in toxic products, such as the transformation of methyleugenol to 1'-hydroxymethyleugenol, estragole to reactive metabolites, and oxidation of nephrotoxins. It also plays an important role in the metabolism of several clinical drugs including analgesics, antipyretics, antipsychotics, antidepressants, anti-inflammatory, and cardiovascular drugs. The CYP1A subfamily belongs to the large cytochrome P450 (P450, CYP) superfamily of heme-containing proteins that catalyze a variety of oxidative reactions of a large number of structurally different endogenous and exogenous compounds in organisms from all major domains of life. CYPs bind their diverse ligands in a buried, hydrophobic active site, which is accessed through a substrate access channel formed by two flexible helices and their connecting loop.
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