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Toxicology. 2000 Apr 3;144(1-3):139-47.

CYP2A6: a human coumarin 7-hydroxylase.

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Department of Pharmacology and Toxicology, University of Oulu, PO Box 5000, FIN-90401, Oulu, Finland.


Coumarin 7-hydroxylation is catalysed by a high-affinity CYP2A6 enzyme in human liver microsomes. CYP2A6 is the only enzyme catalysing this reaction and consequently the formation of 7-hydroxycoumarin can be used as 'an in vitro and in vivo probe' for CYP2A6. CYP2A6 is a major contributor to the oxidative metabolism of nicotine and cotinine, and it also contributes, to a larger or smaller extent, to the metabolism of a few pharmaceuticals (e.g. fadrozole), nitrosamines, other carcinogens (e.g. aflatoxin B1) and a number of coumarin-type alkaloids. CYP2A6 may be inducible by antiepileptic drugs and it is decreased in alcohol-induced severe liver cirrhosis. Several mutated or deleted CYP2A6 alleles have been characterized. Although CYP2A6 represent up to 15% of human microsomes P450 proteins, it is still one of the less well characterised cytochrome P450 enzymes.

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