Cytochrome P4502A6 (CYP2A6) is an isoform that plays
important roles in the metabolism of clinically used drugs,
such as halothane, valproic acid and coumarin, as well as of
environmental and toxic agents, including nicotine and
aflatoxin B1. CYP2A6 polymorphisms were first observed
approximately 10 years ago, when the wild-type
(CYP2A6*1), variant 1 (CYP2A6*2) and variant 2
(CYP2A6*3) alleles were identified. To date, more than 25
allelic variants of CYP2A6 linked to decreases or deficiencies
in CYP2A6 activities have been reported (http://www.
imm.ki.se/CYPalleles/CYP2A6. htm). The earliest genomic
studies found that the most conspicuous of inter-ethnic
differences is that of the deleted CYP2A6*4 allele being
more frequent in Asian than Caucasian populations. In
contrast, CYP2A6*2 is lacking in both Asian and Caucasian
(