BIOSYNTHETIC RESEARCH OF FETAL BILE ACID AND ANALYSIS OF CONGENITAL DISORDER OF BILE ACID BIOSYNTHESIS

为了阐明胎儿胆汁酸的生物合成途径和β-氧化酶系统的底物特异性，并应用于先天性胆汁酸生物合成障碍患者尿液中胆汁酸中间体的测定，建立Zellweger综合征的简便诊断方法<27>。同时合成了中间体的立体异构体和<27>含胎儿胆汁酸前体的C_ -胆汁酸类似物，以明确相关酶（β-氧化酶）的底物和立体选择性。以上述合成标准品为基础，采用GC/MS和HPLC建立了胆汁酸中间体的定量和同时分析方法，并将合成样品与大鼠肝匀浆孵育，用上述分析方法对产物进行了定量测定。结果表明，胎儿胆汁酸（1 β-和6 α-羟基化胆酸）通过β-氧化途径生物合成。对相关酶的底物和立体选择性进行了研究，结果表明，酶的底物特异性与羟基数目有关，对中间体的形成具有高度的立体选择性。应用该方法对1例Zellweger综合征患者尿中胆汁酸进行了分析。定量分析清楚地表明胆汁酸生物合成的β-氧化系统的缺陷。并<27>测定了胎儿胆汁酸的C_ -前体。

To clarify the biosynthetic pathway of fetal bile acids and the substrate specificity of beta-oxidation enzymes system were investigated, and the analytic application of the determination of bile acid intermediates in urine with congenital disorder of bile acid biosynthesis was performed to establish a convenient diagnosis for Zellweger syndrome The intermediates of bile acid biosynthesis (C_<27>-bile acids) were synthesized by the nwely developed synthetic method. The stereoisomers of the intermediates and the C_<27>-bile acid analogues containing the precursor for fetal bile acids were also synthesized to make clear the substrate and stereoselectivity of related enzymes(beta-oxidation enzymes). Using the above synthetic standard, the quantitative and simultaneous analytical methods for bile acid intermediates were developed by GC/MS and HPLC.The incubation of synthetic samples with rat liver homogenate was tired and the products were quantitatively determined by the above analytical methods. The results indicated that fetal bile acids (1beta-and 6alpha-hydroxylated cholic acids) are biologically synthesized through the beta-oxidation pathway. The substrate and stereoselectivity of the related enzymes were also investigated and the results showed the substrate specificity conccrning to the numbers of hydroxyl groups and high stereoselectivity for the formation of intermediates. The analytical method were applied to the analysis of bile acids in urine of a patient of Zellweger syndrome. The quantitative analysis clearly showed the deficiency of beta-oxidation system for bile acid biosynthesis. And the C_<27>-precursor of fetal bile acids were also determined.