An investigation of the catalytic activity of CYP2A13*4 with coumarin and polymorphisms of CYP2A13 in a Chinese Han population.
CYP2A13 has been identified as an efficient catalyst for the metabolisms of coumarin, aflatoxin B(1) (AFB(1)), and several tobacco-specific carcinogens. The reported CYP2A13 polymorphisms with missense variations have been studied for their functional consequences, and CYP2A13*4 (R101Q) variant was found to be a null enzyme in metabolizing 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), AFB(1), and 5-methoxypsoralen. In the present study, CYP2A13*4 was expressed in Sf9 cells and evaluated for coumarin 7-hydroxylation activity. Our results demonstrated that CYP2A13*4 showed no activity in coumarin 7-hydroxylation. Furthermore, computer modeling studies were conducted to probe the mechanisms underlying the loss of catalytic activity of CYP2A13*4. The results suggested that the R101Q alteration may result in the absence of several hydrogen bonds involved in heme binding and thus lead to the loss of function in CYP2A13*4. In addition, for the first time, the distribution frequencies of all eight known CYP2A13 missense alleles were examined in a Chinese Han population. The distribution frequencies of CYP2A13*3 allele and CYP2A13*4 allele in the Chinese Han population were statistically significantly different from the reported values in Japanese. Considering that the two variants of CYP2A13 are incapable of metabolic activation of NNK and AFB(1), the susceptibility to NNK or AFB(1) exposure between the Chinese Han population and Japanese can be different.
Institute of Pharmacology & Toxicology and Biochemical Pharmaceutics, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China.
Ting
T
Liu
Yanjun
Y
Hong
Zhaohui
Z
Li
Junyan
J
Hong
Su
S
Zeng
Mingyue
M
Zheng
Shuqing
S
Chen
D000328:Adult; D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics* / Q000378:metabolism*; D044466:Asian People / Q000235:genetics*; D001665:Binding Sites; D015153:Blotting, Western; D002384:Catalysis; D002460:Cell Line; D003198:Computer Simulation; D003374:Coumarins / Q000378:metabolism* / Q000493:pharmacokinetics; D004247:DNA / Q000235:genetics; D005787:Gene Frequency; D006418:Heme / Q000235:genetics; D006801:Humans; D006900:Hydroxylation; D007313:Insecta; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D020125:Mutation, Missense; D016133:Polymerase Chain Reaction; D020641:Polymorphism, Single Nucleotide
D003374:Coumarins; D006418:Heme; D004247:DNA; C030123:coumarin; D001189:Aryl Hydrocarbon Hydroxylases; C414206:CYP2A13 protein, human