Polymorphism of drug-metabolising enzymes

本课题对目前广泛应用于人体肝脏药物代谢能力评价的三甲双酮代谢酶细胞色素P450同工酶进行了研究。为了建立简便、可靠的基因分型方法，比较了探针药物法测定的表型与基因型的关系，采用人肝微粒体组分和人淋巴母细胞表达的细胞色素P450酶测定了曲美双酮代谢。同时，对28名健康志愿者进行了CYP 2C 19表型与其第5外显子突变基因型、第4外显子突变基因型的相关性研究。28例受试者中有6例在外显子4和外显子5中均为野生型（wt/wt）等位基因纯合子，11例为CYP 2C 19 m1（wt/m1）杂合子; 5例为CYP 2C 19 m2（wt/m2）杂合子; 5例为CYP 2C 19 m1（m1/m1）纯合子; 1例为两种缺陷（m1/m2）杂合子。纯合基因型与快代谢型（EM：wt/wt）和PM（m1/m1）的表型相容。然而，杂合子基因型，是不明确兼容的表型：1/11与wt/m1基因型被判断为PM。5名受试者与wt/m2的EM。由于奥美拉唑和5-OH奥美拉唑的血清浓度极低，无法确定1例m1/m2受试者的表型。由此可见，CYP 2C 19基因型和表型在受试者中具有良好的相关性。需要进一步的详细研究来阐明CYP 2C 19基因型与杂合基因型受试者表型之间的关系。

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.