The mechanistic enzymology of thiamin biosynthesis

硫胺素是人类饮食的重要组成部分，RDA为1.2 mg。它也是一种重要的商业化学品，广泛用作食品添加剂和调味剂。通过化学合成，年产量约为3，300吨。硫胺素依赖酶在碳水化合物和支链氨基酸代谢中起重要作用。目前，我们对这类酶的机械理解是复杂的。相比之下，虽然硫胺素是第一种被发现的维生素，但我们对其生物合成的理解仍然不完整，因为生物合成途径很复杂，涉及前所未有的化学反应。我们的研究的长期目标是完整的机械理解的硫胺素生物合成，抢救和catastrophic的酶学，在所有形式的生命和硫胺素代谢和细胞生理学的其他方面之间的联系的阐明。在下一个资助期，我们描述了旨在阐明细菌和真核生物中硫胺素噻唑和嘧啶的生物合成的研究。这些杂环形成反应涉及新的生物化学。我们的策略将包括动力学、修饰底物、蛋白质 诱变和结构研究。我们还将确定与硫胺素分解和补救有关的基因。人体消化道中含有这些基因的细菌可能在控制人体硫胺素RDA方面发挥重要作用。最后，我们将探索使用18F-硫胺素作为PET显像剂，最终确定健康和患病人群的全球硫胺素分布。 相关性（参见说明）： 硫胺素（维生素B1）是所有生命形式所必需的。本研究为发酵法生产硫胺素奠定了基础，并在新型抗生素的设计中具有潜在的应用价值。了解维生素B1的催化作用和补救作用将使我们能够评估这些活动在人体消化道中的重要性。18F-硫胺素作为一种显像剂，在基础人类生物学和肿瘤检测中具有潜在的用途。

Thiamin is an essential component of the human diet with an RDA of 1.2 mg. It is also an important commercial chemical and it is widely used as a food additive and flavoring agent. Annual production, by chemical synthesis, is on the order of 3,300 tons. Thiamin-dependent enzymes play an important role in carbohydrate and branched-chain amino acid metabolism. At this time, our mechanistic understanding of this class of enzymes is sophisticated. In contrast, while thiamin was the first vitamin identified, our understanding of its biosynthesis is still incomplete because the biosynthetic pathway is complex and involves unprecedented reaction chemistry. The long-term goal of our research is the complete mechanistic understanding of the enzymology of thiamin biosynthesis, salvage and catabolism, in all forms of life and the elucidation of connections between thiamin metabolism and other aspects of cellular physiology. In the next grant period, we describe studies designed to elucidate the biosynthesis of the thiamin thiazole and pyrimidine in both bacteria and eukaryotes. These heterocycle forming reactions involve novel biological chemistry. Our strategy will involve a combination of kinetics, modified substrates, protein mutagenesis and structural studies. We will also identify the genes involved in thiamin breakdown and salvage. Bacteria, in the human digestive tract, containing these genes are likely to play an important role in controlling the human thiamin RDA. Finally, we will explore the use of 18F-thiamin as a PET imaging agent, ultimately to determine the global thiamin distrubution in healthy and diseased humans. RELEVANCE (See instructions): Thiamin (vitamin B1) is essential for all forms of life. Our studies will facilitate the commercial production of thiamin by fermentation and have potential applications in the design of new antibiotics. Understanding thiamin catabolism and salvage will enable us to evaluate the importance of these activities in the human digestive tract. 18F-thiamin has potential use, as an imaging agent, in basic human biology and in tumor detection.