BIOSYNTHESIS OF VITAMIN B1 AND VITAMIN B6

描述(改编自申请者摘要)：60多年后 吡哆醇(维生素B6)和硫胺素的发现和合成 (维生素B1)和对其营养重要性的认识，等等 在它们的生化功能被阐明30多年后， 对通向每种化合物的生物合成途径的了解仍然 支离破碎。本提案的目的是进一步 阐明这两种维生素的生物合成，更具体地说， 在新陈代谢路线上寻找承诺的前体到每一个。 根据放射性示踪剂的掺入研究结果， 这表明，这两种维生素的碳链都是从 从碳水化合物前体出发，已经提出了工作假说 解释了吡哆醇的生物合成机制以及每一种 硫胺素的两个亚基与高级结构 中间体。在目前的授权期内，它打算测试这些 提案。1-脱氧-D-木酮糖和4-羟基-L苏氨酸 在大肠杆菌中合成并测试了吡哆醇的前体。三 将采用的方法，如果成功，将提供令人信服的 支持这两种化合物的中间体的证据：(1) 在有(6-13C)葡萄糖存在时标记的掺入置换 1-脱氧-D-木果糖和4-羟基-L-苏氨酸的未标记样品；(2) 从1-脱氧-D-木果糖和13C标记样品中掺入标记 4-羟基-L-苏氨酸；和(3)~3H/~(14)C标记的捕获 1-脱氧-D-木果糖和4-羟基-L-苏氨酸 从~3H/~(14)C标记的甘油中得到~3H/~(14)C标记的吡哆醇。如果 1-脱氧-D-木果糖被确认为中间体，其氧化产物， 2，4-二氧戊烷-3，5-二醇，将进行类似的测试。成立为法团 ~(13)C标记的1-脱氧-D-木聚果糖进入其噻唑核的C5链 硫胺素和~(13)C标记的己糖进入嘧啶核 将进行测试，试图为以下未决问题提供答案 它们的起源。很明显，B1和B1的主要前驱物质 B6是常见的代谢物。这是它的长期目标 调查以确定每条通路中受阻的步骤 哺乳动物组织，从而使化合物成为必需的饮食 组件。

DESCRIPTION (adapated from applicant's abstract): More than 60 years after the discovery and synthesis of pyridoxine (vitamin B6) and of thiamin (vitamin B1) and the recognition of their nutritional importance, and more than 30 years after the elucidation of their biochemical functions, knowledge of the biosynthetic pathways leading to each compound is still fragmentary. The objectiveof the present proposal is the further elucidation of the biosynthesis of the two vitamins and, more specifically, the search for committed precursors on the metabolic route to each of them. Based on the results of incorporation studies with radioactive tracers, which showed that the carbon chains of each of the two vitamins are derived from carbohydrate precursors, working hypotheses have been put forward that account for the mechanism of biosynthesis of pyridoxine and of each of the two subunits of thiamin and that postulate structures of advanced intermediates. In the present grant period it is intended to test these proposals. 1-Deoxy-D-xylulose and 4-hydroxy-L-threonine will be synthesized and tested as precursors of pyridoxine in E. coli. Three approaches will be employed which, if successful, would provide compelling evidence in support of the intermediacy of these two compounds: (1) displacement of incorporation of label from (6-13C)glucose in the presence of unlabeled samples of 1-deoxy-D-xylulose and 4-hydroxy-L-threonine; (2) incorporation of label from 13C-labeled samples of 1-deoxy-D-xylulose and 4-hydroxy-L-threonine; and (3) trapping of 3H/14C-labeled 1-deoxy-D-xylulose and 4-hydroxy-L-threonine from an E. coli culture that has yielded 3H/14C-labeled pyridoxine from 3H/14C-labeled glycerol. If 1-deoxy-D-xylulose is confirmed as an intermediate, its oxidationproduct, 2,4-dioxopentane-3,5-diol, will be tested similarly. Incorporation of 13C-labeled 1-deoxy-D-xylulose into the C5 chain of the thiazole nucleus of thiamin and of specifically 13C-labeled hexoses into the pyrimidine nucleus will be tested in an attempt to provide answers to outstanding questions of their origin. It is becoming evident that the primary precursors of B1 and B6 are common metabolites. It is the long term objectiveof this investigation to identify the step in each pathway that is blocked in mammalian tissues, thereby making the compounds essential dietary components.