MOLECULAR BIOLOGY OF SECONDARY BILE ACID SYNTHESIS

据报道，脱氧胆酸（DCA）在 人类结肠癌和胆固醇结石病的病因。 高水平的疏水性二级胆汁酸也可能有助于 某些胆汁淤积性肝病的病理生理学。DCA是 由一小群革兰氏阳性菌从胆酸（CA）中形成 肠道厌氧菌 人体胆汁中的DCA水平可以 范围从0到> 40%。 CA到DCA的转换通过六个步骤进行 生化途径 Th基因编码胆汁酸中的酶 7 α-脱羟基（7 α-DeOH）途径位于一个大的 真杆菌属VPI 12708中胆汁酸诱导（bai）操纵子。 然而，初步数据表明，bai基因与 只有大约50%的其他6 α-DeOH肠道细菌的DNA。 本研究的目的是克隆、测序和分析Bai操纵子， 梭菌菌株T0931是一株高活性菌株，其DNA 不与来自Eurobium sp.VPI12708的bai基因杂交。这 信息对于更全面地了解 参与胆汁酸7 α- DeOH。 具体目标2是表达E.大肠杆菌，纯化和表征 真杆菌属VPI 12708的baIF基因产物。 初步 数据表明该基因编码一种新的胆汁酸-CoA水解酶。 胆汁酸的遗传学和酶学研究进展 7 α-DeOH对于开发特异性抑制剂至关重要 这条路。

Deoxycholic acid (DCA) has been reported to play a role in the etiology of colon cancer and cholesterol gallstone disease in man. High levels of hydrophobic secondary bile acids may also contribute to the pathophysiology of certain cholestatic liver diseases. DCA is formed from cholic acid (CA) by a small population of gram-positive intestinal anaerobic bacteria. The levels of DCA in human bile can range from 0 to >40%. CA conversion to DCA occurs via a six step biochemical pathway. Th genes encoding enzymes in the bile acid 7alpha-dehydroxylation (7alpha-DeOH) pathway are located on a large bile acid inducible (bai) operon in Eubacteriim sp. VPI 12708. However, preliminary data indicates that the bai genes hybridize to DNA from only about 50% of other 6alpha-DeOH intestinal bacteria. Specific Aim1 is to clone, sequence and analyze the bai operon from Clostridum sp. Strain T0931, a high activity strain whose DNA does not hybridize to bai genes from Eubacterum sp. VPI12708 . This information will be essential for a more complete understanding of the origin and evolution of enzymes involved in bile acid 7alpha- DeOH. Specific Aim 2 is to express E. Coli, purify and characterize the baiF gene product for Eubacterium sp. VPI 12708. Preliminary data indicate that this gene encodes a novel bile acid-CoA hydrolase. A better understanding of the genetics and enzymology of bile acid 7alpha-DeOH is essential for the development of specific inhibitors of this pathway.