Abstract
Although many cases of interindividual variation in the metabolism of CYP2C19 drugs are explained by the CYP2C19*2, *3, and *17, a wide range of metabolic variation still occurs in people who do not carry these genetic variants. The objectives of this study were to identify new genetic variants and to characterize functional consequences of these variants in metabolism of CYP2C19 substrates. In total, 21 single-nucleotide polymorphisms including three new coding variants, V394M, E405K, and D256N, were identified by direct DNA sequencing in 50 randomly selected subjects and in individuals who exhibited an outlier phenotype response in the omeprazole study. Recombinant proteins produced from the coding variants V394M, E405K, and D256N were prepared by using an Escherichia coli expression system and purified. Metabolism of S-mephenytoin and omeprazole by V394M was comparable with that of the wild-type protein. E405K showed a moderate decrease in metabolism of the substrates. However, D256N exhibited a significantly decreased activity in S-mephenytoin metabolism, resulting in 50 and 76% decreases in Vmax and intrinsic clearance, respectively, compared with the wild type. This variant also exhibited a significant decrease in omeprazole metabolism in vivo. CYP2C19 D256N and E405K were assigned as CYP2C19*26 and *2D, respectively, by the Cytochrome P450 Nomenclature Committee. In summary, this report characterizes the allele frequency and haplotype distribution of CYP2C19 in a Korean population and provides functional analysis of new coding variants of the CYP2C19 gene. Our findings suggest that individuals carrying CYP2C19*26 would have lower activity for metabolizing CYP2C19 substrate drugs.
- P450, cytochrome P450
- PM, poor metabolizer
- IPTG, isopropyl β-d-thiogalactopyranoside
- MR, metabolic ratio
- PCR, polymerase chain reaction
- SNP, single-nucleotide polymorphism
- bp, base pair
- 5′-UTR, 5′-untranslated region.
Footnotes
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This study was supported by a Korea Science and Engineering Foundation grant funded by the Ministry of Education, Science and Engineering, Korea [Grant R13-2007-023-00000-0]; and a grant from the Korea Health 21 R&D Project, Ministry for Health, Welfare and Family Affairs, Republic of Korea [Grant A030001].
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Article, publication date, and citation information can be found at http://dmd.aspetjournals.org.
doi:10.1124/dmd.109.028175
- Received April 21, 2009.
- Accepted July 31, 2009.
- Copyright © 2009 by The American Society for Pharmacology and Experimental Therapeutics
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