The mechanistic enzymology of thiamin biosynthesis

硫胺素是人类饮食中的基本成分，RDA为1.2毫克。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。化学合成法的年产量约为3300吨。硫胺素依赖的酶在碳水化合物和支链氨基酸代谢中起着重要作用。在这个时候，我们对这类酶的机制理解是复杂的。相比之下，尽管硫胺素是第一个被发现的维生素，但我们对其生物合成的了解仍然不完整，因为生物合成途径复杂，涉及前所未有的反应化学。我们研究的长期目标是对所有生命形式中硫胺素生物合成、回收和分解代谢的酶学机制进行完整的了解，并阐明硫胺素代谢和细胞生理的其他方面之间的联系。在下一个授权期，我们将介绍旨在阐明硫胺素、噻唑和嘧啶在细菌和真核生物中的生物合成的研究。这些杂环形成反应涉及到新的生物化学。我们的战略将涉及动力学、修饰底物、蛋白质的组合 诱变和结构研究。我们还将确定与硫胺素分解和回收有关的基因。人类消化道中含有这些基因的细菌很可能在控制人类硫胺素RDA方面发挥重要作用。最后，我们将探索18F-硫胺素作为PET显像剂的使用，最终确定硫胺素在健康和疾病人群中的全球分布。 相关性(请参阅说明)： 硫胺素(维生素B1)对所有形式的生命都是必不可少的。我们的研究将促进硫胺素的工业化发酵生产，并在设计新的抗生素方面具有潜在的应用价值。了解硫胺素的分解代谢和回收将使我们能够评估这些活动在人类消化道中的重要性。18F-硫胺素作为一种显像剂，在基础人体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.