Lee Su-Jun, Usmani Khawja A, Chanas Brian, Ghanayem Burhan, Xi Tina, Hodgson Ernest, Mohrenweiser Harvey W, Goldstein Joyce A
Human Metabolism Section, Laboratory of Pharmacology and Chemistry, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA.
Pharmacogenetics. 2003 Aug;13(8):461-72. doi: 10.1097/00008571-200308000-00004.
Genetic polymorphisms of cytochromes P450 (CYPs) are a principal reason for inter-individual variations in the metabolism of therapeutic drugs and environmental chemicals in humans. The present study identifies 34 single nucleotide polymorphisms (SNPs) of CYP3A5 including 27 previously unidentified SNPs by direct sequencing of the exons, intron-exon junctions and 5'-upstream region of CYP3A5 from 92 racially diverse individuals (24 Caucasians, 24 Africans, 24 Asians, and 20 individuals of unknown racial origin).
Four new CYP3A5 SNPs produced coding changes: R28C, L82R, A337T, and F446S. CYP3A5 R28C occurred in African populations (allelic frequency of 4%). CYP3A5 A337T occurred in Asians (2% allelic frequency), CYP3A5 L82R (occurred in the racially unidentified group) and CYP3A5 F446S (identified in Caucasians with a 2% allelic frequency) were on an allele containing the splice change g.6986A>G known as CYP3A53. The newly identified allelic proteins were constructed by site-directed mutagenesis, expressed in Escherichia coli and purified. CYP3A5 L82R was expressed only as denatured CYP420, suggesting it may be unstable. CYP3A51 exhibited the highest maximal clearance for testosterone followed by CYP3A5 A337T > CYP3A5 R28C >> CYP3A5 F446S. CYP3A51 exhibited a higher V(max) for nifedipine oxidation than CYP3A5 A337T > CYP3A5 R28C >> CYP3A5 F446S. CYP3A5 A337T and CYP3A5 R28C exhibited a 42-64% lower V(max) for nifedipine oxidation than CYP3A51. CYP3A5 F446S exhibited a > 95% decrease in the intrinsic clearance for both 6beta-hydroxytestosterone and nifedipine oxidation.
This study identifies four new potentially defective coding alleles. CYP3A5 F446S is predicted to be more catalytically defective than the splice change alone.
细胞色素P450（CYPs）的基因多态性是人类治疗药物和环境化学物质代谢个体差异的主要原因。本研究通过对92名不同种族个体（24名高加索人、24名非洲人、24名亚洲人和20名种族来源不明个体）的CYP3A5外显子、内含子 - 外显子连接区和5' - 上游区域进行直接测序，鉴定出34个单核苷酸多态性（SNP），其中包括27个先前未鉴定的SNP。
四个新的CYP3A5 SNP产生了编码变化：R28C、L82R、A337T和F446S。CYP3A5 R28C出现在非洲人群中（等位基因频率为4%）。CYP3A5 A337T出现在亚洲人群中（等位基因频率为2%），CYP3A5 L82R（出现在种族不明的群体中）和CYP3A5 F446S（在高加索人群中鉴定出，等位基因频率为2%）位于一个包含剪接变化g.6986A>G的等位基因上，该变化被称为CYP3A53。通过定点诱变构建新鉴定的等位基因蛋白，在大肠杆菌中表达并纯化。CYP3A5 L82R仅以变性的CYP420形式表达，表明它可能不稳定。CYP3A51对睾酮的最大清除率最高，其次是CYP3A5 A337T > CYP3A5 R28C >> CYP3A5 F446S。CYP3A51对硝苯地平氧化的V(max)高于CYP3A5 A337T > CYP3A5 R28C >> CYP3A5 F446S。CYP3A5 A337T和CYP3A5 R28C对硝苯地平氧化的V(max)比CYP3A51低42 - 64%。CYP3A5 F446S对6β - 羟基睾酮和硝苯地平氧化的内在清除率均降低> 95%。
本研究鉴定出四个新的潜在缺陷编码等位基因。预计CYP3A5 F446S的催化缺陷比单独的剪接变化更大。
