Polymorphism of drug-metabolising enzymes

在本项目中，我们已经确定了与三甲二酮代谢有关的细胞色素P450同工酶，该同工酶被广泛用于评估人体体内肝脏药物代谢能力。同时，为了建立简便、可靠的基因分型方法，比较了探针药物测定的表型与基因分型的关系。用人肝微体部分和人淋巴母细胞表达细胞色素P450酶测定了甲氧西酮的代谢。通过这些实验，确定了甲氧西酮在人体内主要由CYP2E1酶代谢。另一方面，通过对28名表型新兵健康志愿者的研究，确定了这两对突变的表型与其表型的关系，即外显子5的CYP2C19m1和外显子4的CYP2C19m2。在28例受试者中，6例同时存在野生型(wt/wt)等位基因，11例存在CYP2C19m1杂合子(wt/m1)，5例存在CYP2C19m2杂合子(wt/m2)，5例存在CYP2C19m1杂合子(m1/m1)，1例同时存在两种缺陷(m1/m2)。纯合子基因与广泛代谢型(Ems：wt/wt)和Pms(m1/m1)表型一致。然而，杂合子与表型并不明显相容：11例wt/m1基因携带者中有1例被判定为PM，5例wt/m2受试者为EM。由于奥美拉唑和5-羟基奥美拉唑的血清浓度极低，1名m1/m2的受试者的表型无法确定。从这些结果可以看出，在受试者中，CYP2C19的基因型和表型有很好的相关性。在杂合基因受试者中，需要进一步的详细研究来阐明CYP2C19基因与表型之间的关系。

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.