Genetic polymorphisms in human CYP2A6 gene causing impaired nicotine metabolism.
OBJECTIVE
Previously, we determined the phenotyping of in vivo nicotine metabolism and the genotyping of the CYP2A6 gene (CYP2A6*1 A, CYP2A6*1B, CYP2A6*2, CYP2A6*3, CYP2A6*4 and CYP2A6*5 ) in 92 Japanese and 209 Koreans. In the study, we found one Korean and four Japanese subjects genotyped as CYP2A6*1B/CYP2A6*4 who revealed impaired nicotine metabolism, although other many heterozygotes of CYP2A6*4 demonstrated normal nicotine metabolism (CYP2A6*4 is a whole deletion type). After our previous report, several CYP2A6 alleles, CYP2A6*6 (R128Q), CYP2A6*7 (I471T), and CYP2A6*8 (R485L), have been reported. The purpose of the present study was to clarify whether the impaired nicotine metabolism can be ascribed to these CYP2A6 alleles. Furthermore, we also determined whether the subjects possessing CYP2A6*1x2 (duplication) reveal higher nicotine metabolism.


METHODS
Genotyping of CYP2A6 alleles, CYP2A6*6, CYP2A6*7, CYP2A6*8, and CYP2A6*1x2 was determined by PCR.


RESULTS
The five poor metabolizers were re-genotyped as CYP2A6*7/CYP2A6*4, suggesting that a single nucleotide polymorphism (SNP) causing I471T decreases nicotine metabolism in vivo. Furthermore, we found that two subjects out of five with a lower potency of nicotine metabolism possessed SNPs of CYP2A6*7 and CYP2A6*8 simultaneously. The novel allele was termed CYP2A6*10. In the 92 Japanese and 209 Koreans, the CYP2A6*6 allele was not found. The allele frequencies of CYP2A6*7, CYP2A6*8, and CYP2A6*10 were 6.5%, 2.2%, and 1.1%, respectively, in Japanese, and 3.6%, 1.4%, and 0.5%, respectively, in Koreans. The CYP2A6*1x2 allele was found in only one Korean subject (0.5%) whose nicotine metabolic potency was not very high.


CONCLUSIONS
It was clarified that the impaired in vivo nicotine metabolism was caused by CYP2A6*7 and CYP2A6*10 alleles.
Yoshida
Ryoko
R
Division of Drug Metabolism, Faculty of Pharmaceutical Sciences, Kanazawa University, Takara-machi 13-1, Kanazawa 920-0934, Japan.
Nakajima
Miki
M
Watanabe
Yuki
Y
Kwon
Jun-Tack
JT
Yokoi
Tsuyoshi
T
D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics*; D001483:Base Sequence; D065637:Cytochrome P-450 CYP2A6; D005731:Ganglionic Stimulants / Q000378:metabolism*; D005838:Genotype; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D007564:Japan / Q000208:ethnology; D007723:Korea / Q000208:ethnology; D006899:Mixed Function Oxygenases / Q000235:genetics*; D009538:Nicotine / Q000031:analogs & derivatives / Q000235:genetics / Q000378:metabolism*; D018722:Nicotinic Agonists / Q000378:metabolism*; D011109:Polymethacrylic Acids / Q000378:metabolism; D011110:Polymorphism, Genetic / Q000235:genetics*; D011145:Polyvinyls / Q000378:metabolism; D017422:Sequence Analysis, DNA; D061485:Tobacco Use Cessation Devices
D005731:Ganglionic Stimulants; D018722:Nicotinic Agonists; D011109:Polymethacrylic Acids; D011145:Polyvinyls; D009538:Nicotine; D006899:Mixed Function Oxygenases; D001189:Aryl Hydrocarbon Hydroxylases; C585710:CYP2A6 protein, human; D065637:Cytochrome P-450 CYP2A6