Mechanisms of Biosynthetic Formation of Deoxy Sugars

描述（由申请人提供）：许多具有生物活性的天然产物的活性来自其结构的糖成分。改变这些糖的结构可以对母体化合物的生物活性、选择性和药代动力学特性产生深远的影响。这一观察结果推动了利用糖生物合成机制衍生出不同糖部分的天然产物的方法的发展。要充分发挥这种方法的潜力，不仅需要发现新的糖生物合成途径，还需要对每种靶糖的生物合成途径有透彻的了解，包括对关键酶的详细机制知识。有了这些目标，我们在以前的资助下取得了显著的成果。根据这些研究，我们确定了四个关键领域，值得在下一个供资期进一步调查。因此，本应用程序概述了旨在了解去糖胺，apiose， kijanose和2-脱氧-2-巯基葡萄糖是如何生物合成的实验。具体目标包括：(1)参与脱糖胺生物合成的自由基- sam酶（DesII）的机制研究，脱糖胺是许多大环内酯类抗生素的重要组成部分，(2)确定由UDP-apiose合成酶催化的吡喃糖到呋喃糖环收缩的机制，(3)对kijanimicin不寻常的硝基糖部分（kijanose）的生物合成进行调查，(4)阐明硫掺入抗生素BE-7585A的2-脱氧-2-巯基葡萄糖片段的机制。提出的实验不仅将描述脱氧，支链，硝基和含硫糖的生物合成，而且将通过加强我们对几种重要酶类的理解来推进机械酶学领域。我们的研究结果对应用生物医学研究也有价值，因为新的糖基化工具（即糖生物合成途径和酶）将被发现，用于未来的次级代谢物糖多样化工作。公共卫生相关性：本应用程序概述了旨在研究自由基SAM酶DesII机制的实验，DesII参与脱糖胺生物合成中的c4脱氧步骤，UDP-apiose合成酶（Axs1）催化的环收缩反应机制，一种不寻常的硝基糖kijanose的生物合成以及硫结合到BE-7585A的硫糖部分的机制。这一结果有望显著推进机制酶学领域的发展，并对应用生物医学研究具有重要价值，因为未来将发现新的糖生物合成途径和酶，用于次级代谢物糖多样化的研究。

DESCRIPTION (provided by applicant): Many biologically active natural products derive their activity from the sugar components of their structures. Changing the structures of these sugars can have a profound impact on the biological activity, selectivity, and pharmacokinetic properties of the parent compounds. This observation has fueled the development of methods to derivatize natural products with diverse sugar moieties by exploiting the sugar biosynthetic machinery. Fully realizing the potential of such an approach relies on the discovery of new sugar biosynthetic pathways, and also requires a thorough understanding of the biosynthetic pathway of each target sugar including detailed mechanistic knowledge of the key enzymes. With these goals in mind, we have produced notable results in work funded by previous grant. As a result of these studies, we have identified four key areas that warrant further investigation in the next funding period. Accordingly, this application outlines experiments designed to learn how desosamine, apiose, kijanose, and 2-deoxy-2- mercaptoglucose are biosynthesized. The specific objectives include (1) mechanistic studies of a radical-SAM enzyme (DesII) involved in the biosynthesis of desosamine, an essential component of many macrolide antibiotics, (2) a determination of the mechanism of the pyranose-to-furanose ring-contraction catalyzed by UDP-apiose synthase, (3) an investigation into the biosynthesis of the unusual nitrosugar moiety (kijanose) of kijanimicin, and (4) the elucidation of the mechanism of sulfur incorporation into the 2-deoxy-2-mercaptoglucose moiety of the antibiotic BE-7585A. The proposed experiments will not only delineate the biosynthesis of deoxy-, branched-chain, nitro-, and sulfur-containing sugars, but will also advance the field of mechanistic enzymology by enhancing our understanding of several important classes of enzymes. Our results should also be valuable to applied biomedical research, as new glycosylation tools (i.e., sugar biosynthetic pathways and enzymes) will be discovered for future secondary metabolite glycodiversification efforts. PUBLIC HEALTH RELEVANCE: Outlined in this application are experiments designed to study the mechanism of the radical SAM enzyme, DesII, involved in the C4-deoxygenation step in desosamine biosynthesis, the mechanism of the ring contraction reaction catalyzed by UDP-apiose synthase (Axs1), the biosynthesis of an unusual nitrosugar, kijanose, and the mechanism of sulfur incorporation into the thiosugar moiety of BE-7585A. The results are expected to significantly advance the field of mechanistic enzymology and should also be valuable to applied biomedical research, as new sugar biosynthetic pathways and enzymes will be discovered for future secondary metabolite glycodiversification efforts.