Dai D, Tang J, Rose R, Hodgson E, Bienstock R J, Mohrenweiser H W, Goldstein J A
National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA.
J Pharmacol Exp Ther. 2001 Dec;299(3):825-31.
CYP3A4 is the most abundant isoform of cytochrome P450 (CYP) in adult human liver. It metabolizes numerous clinically, physiologically, and toxicologically important compounds. The expression of CYP3A4 varies 40-fold in individual human livers, and metabolism of CYP3A4 substrates varies at least 10-fold in vivo. Single nucleotide polymorphisms (SNPs) in CYP3A4 were identified by direct sequencing of genomic DNA in 72 individuals from three different ethnic groups, including Caucasians, Blacks (African-Americans and African pygmies), and Asians. A total of 28 SNPs were identified, including five which produced coding changes M445T (CYP3A43), R162Q (CYP3A415), F189S (CYP3A417), L293P (CYP3A418), and P467S (CYP3A419). The latter four represent new alleic variants. Racial variability was observed for the frequency of individual SNPs. CYP3A R162Q was identified only in Black populations with an allelic frequency of 4%. CYP3A4 F189S and CYP3A4 M445T were identified in Caucasians with allelic frequencies 2% and 4%, respectively. L293P and P467S were only observed in Asians at allelic frequencies of 2%. The cDNAs for the F189S, L293P, M445T, and P467S mutant alleles were constructed by site-directed mutagenesis and expressed in an Escherichia coli expression system. Testosterone and the insecticide chlorpyrifos were used to assess the catalytic activities of the most common CYP3A4 allele (CYP3A41) and its allelic variants. CYP3A4 F189S exhibited lower turnover numbers for testosterone and chlorpyrifos, while CYP3A4 L293P had higher turnover numbers for both substrates. The turnover numbers of the CYP3A4 M445T and P467S alleles to metabolize these compounds were not significantly different from those of wild-type CYP3A4.
细胞色素P450（CYP）3A4是成年人类肝脏中含量最丰富的同工酶。它能代谢众多临床上、生理上和毒理学上重要的化合物。CYP3A4在个体人类肝脏中的表达差异达40倍，其底物在体内的代谢差异至少达10倍。通过对来自三个不同种族群体（包括白种人、黑人[非裔美国人和非洲俾格米人]以及亚洲人）的72名个体的基因组DNA进行直接测序，鉴定出了CYP3A4中的单核苷酸多态性（SNP）。共鉴定出28个SNP，其中5个导致编码改变，分别为M445T（CYP3A43）、R162Q（CYP3A415）、F189S（CYP3A417）、L293P（CYP3A418）和P467S（CYP3A419）。后四个代表新的等位基因变体。观察到个体SNP频率存在种族差异。CYP3A R162Q仅在黑人种群中被鉴定出，等位基因频率为4%。CYP3A4 F189S和CYP3A4 M445T分别在白种人中被鉴定出，等位基因频率分别为2%和4%。L293P和P467S仅在亚洲人中被观察到，等位基因频率为2%。通过定点诱变构建了F189S、L293P、M445T和P467S突变等位基因的cDNA，并在大肠杆菌表达系统中进行表达。使用睾酮和杀虫剂毒死蜱来评估最常见的CYP3A4等位基因（CYP3A41）及其等位基因变体的催化活性。CYP3A4 F189S对睾酮和毒死蜱的周转数较低，而CYP3A4 L293P对这两种底物的周转数较高。CYP3A4 M445T和P467S等位基因代谢这些化合物的周转数与野生型CYP3A4的周转数无显著差异。
