Polymorphism of drug-metabolising enzymes

在本项目中，我们指定了负责甲美二酮代谢的细胞色素P450同工酶，该酶被广泛用于估计人体内肝脏药物代谢能力。为建立简单可靠的酶缺乏症基因分型评价方法，比较了探针药物测定的表型与基因分型的关系。采用人肝微粒体片段和人淋巴母细胞样细胞表达细胞色素P450酶测定甲美二酮代谢。通过这些实验，确定了甲美二酮在人体内主要由CYP2E1酶代谢。另一方面，利用28名健康志愿者，检测5外显子CYP2C19m1和4外显子CYP2C19m2这对突变的基因型与CYP2C19表型之间的关系。28名受试者中有6人外显子4和外显子5的野生型等位基因（wt/wt）为纯合子，11人CYP2C19m1为杂合子（wt/m1）；CYP2C19m2杂合子5个（wt/m2）；CYP2C19m1纯合子为5个（m1/m1）；两个缺陷各有1个杂合子（m1/m2）。纯合子基因型与广泛代谢物（EMs: wt/wt）和pm （m1/m1）的表型一致。然而，杂合基因型与表型不明显相容：11个wt/m1基因型中有1个被判断为PM。wt/m2的5例受试者为EMs。由于奥美拉唑和5-OH奥美拉唑的血清浓度极低，1例m1/m2的表型无法确定。由此可见，CYP2C19基因型和表型在受试者中具有良好的相关性。在杂合型受试者中，CYP2C19基因型与表型之间的关系需要进一步的详细研究。

In this project, we have specified the cytochrome P450 isozyme that responsible to trimethadione metabolism which widely employed for the estimation of hepatic drug-metabolizing capacity in human in vivo. And also to establish the simple and reliable procedure for the evaluate the enzyme deficiency by genotyping procedure, relationship between phenotype determined by employing the probe drug and genotype were compared.Trimethadione metabolism had been determined by employing the human liver microsomal fraction and human lymphoblastoid cell expressed cytochrome P450 enzymes. By these experiments, it had been defined that trimethadione is predominantly metabolyzed by CYP2E1 enzyme in human.On the other hand, relationship between CYP2C19 phenotype and genotype of the couple of mutations, CYP2C19m1 in exon 5 and CYP2C19m2 in exon 4 were determined by using the 28 of phenotyped recruted healthy volunteers. Six out of 28 subjects were homozygous for the wild-type (wt/wt) allele in both exon 4 and exon 5,11 heterozygous for the CYP2C19m1 (wt/m1) ; 5 heterozygous for the CYP2C19m2 (wt/m2) ; 5 homozygous for the CYP2C19m1 (m1/m1) ; 1 heterozygous for both defects (m1/m2). The homozygous genotype was compatible with the phenotype of the extensive metabolizer (EMs : wt/wt) and PMs (m1/m1). The heterozygous genotype, however, was not clearly compatible with the phenotype : one out of 11 with wt/m1 genotype was judged as PM.Five subjects with wt/m2 were EMs. The phenotype of one subject with m1/m2 could not be identified since extremely low serum concentration of omeprazole and 5-OH omeprazole. From these results, genotype and phenotype of CYP2C19 were well correlated among the subjects. Further detail study will be needed to clarify the relationship between the CYP2C19 genotype and phenotype in subjects with a heterozygous genotype.