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学。 高水平的疏水性次级胆汁酸也可能是 对某些胆汁淤积性肝病的病理生理学的影响。DCA是 由胆酸(CA)由一小部分革兰氏阳性菌形成 肠道厌氧菌。人胆汁中DCA的水平可以 范围从0到&gt；40%。CA向DCA的转换通过六个步骤进行 生化途径。胆汁酸中编码酶的TH基因 7α-脱羟基(7α-DeOH)途径位于一个较大的 真细菌胆汁酸诱导(BAI)操纵子VPI为12708。 然而，初步数据表明，BAI基因与 只有大约50%的其他6Alpha-DeOH肠道细菌的DNA。 特异性Aim1是克隆、测序和分析白蛋白操纵子 梭状芽孢杆菌。菌株T0931，一种高活性菌株，其DNA具有 不与真细菌的BAI基因杂交。VPI12708。这 信息对于更全面地理解 胆汁酸7α相关酶的起源和进化 脱氢。特异性目的2是表达、纯化和鉴定大肠杆菌 真核细菌的BaiF基因产物。VPI为12708。初步 数据表明，该基因编码一种新的胆汁酸-辅酶A水解酶。 更好地了解胆汁酸的遗传学和酶学 7α-脱氢酶对特定抑制剂的开发是必不可少的 在这条道路上。

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.