New chemoenzymatic methods for synthesizing complex carbohydrates

在此输入文本，它是您的应用程序的新摘要信息。此部分不得超过30行 文本。 复合碳水化合物在生物系统中扮演着重要的角色。然而，要获得这些是非常困难的。 通过与自然隔离或通过化学合成而形成的纯均一形式的结构。因此， 详细的构效关系通常不清楚，即使对于具有重要结构的已知化合物也是如此 功能。本项目的最终目标是开发新的化学酶合成方法，以有效地 获得具有合成挑战性的碳水化合物和类似物，其数量足够大，足以 表征、功能研究和治疗应用。在当前的资助期内，我们将 重点研究了肝素和硫酸肝素低聚糖类似物的合成。 我们假设N-硫化类似物可以模拟肝素/HS寡糖与其靶标结合 蛋白质，并具有相似的生物活性。此外，N-硫化类似物与合成可控的N-硫酸盐类似物。 硫酸盐化模式可以是探索单个硫酸盐的重要作用的强大工具，并提供关键的 有关O-硫化在功能性肝素/HS寡糖中的单独作用的信息。为了测试这一点 假设，我们建议合成一系列N3修饰的GlcNAc或Glca衍生物，这些衍生物可以用作 UDP-GlcNAc和UDP-GLCA生物合成酶和肝素合成酶的底物生产N3- 含有低聚糖。然后叠氮基团可以被还原为氨基，然后 化学N-硫化提供肝素/HS寡糖的N-硫化类似物以测试其活性。 四个具体目标是1)化学合成N-乙酰氨基葡萄糖(GlcNAc)和糖醛酸衍生物作为 单糖前体；2)UDP-GlcNAc、UDP-糖醛酸及其衍生物的合成；3) 肝素和硫酸肝素低聚糖类似物的酶促合成；4) 使用肝素/硫酸肝素结合蛋白进行构效关系(SAR)研究。此外，我们还将 与我们的同事和长期合作伙伴、结构生物学家专家安德鲁·费希尔教授合作 在蛋白质晶体结构研究方面具有专门知识，以解决肝素的晶体结构问题 合成酶，是组装肝素/HS多糖结构的重要酶。这个 学习到的信息和获得的产品将有助于发现和开发新的 治疗学。

Enter the text here that is the new abstract information for your application. This section must be no longer than 30 lines of text. Complex carbohydrates play important roles in biological systems. However, it is very difficult to obtain these structures in pure homogeneous forms either by isolation from nature or by chemical synthesis. Therefore, the detailed structure-activity relationship is usually not clear, even for well known compounds with important functions. The ultimate goal of this project is to develop novel chemoenzymatic synthetic methods to efficiently obtain synthetically challenging carbohydrates and analogs in amounts large enough for structural characterization, functional studies, and therapeutic applications. For the current funding period, we are focusing on the synthesis of heparin and heparan sulfate (HS) oligosaccharide analogs. We hypothesize that N-sulfated analogs can mimic heparin/HS oligosaccharides for binding to their target proteins and have similar bioactivities. In addition, the N-sulfated analogs with synthetically controllable N- sulfation patterns can be powerful tools to probe the important roles of individual sulfations and provide critical information about individual roles of related O-sulfation in functional heparin/HS oligosaccharides. To test this hypothesis, we propose to synthesize a list of N3-modified GlcNAc or GlcA derivatives that can be used as substrates for UDP-GlcNAc and UDP-GlcA biosynthetic enzymes and heparosan synthases for producing N3- containing oligosaccharides. The azido group can then be reduced to an amino group and followed by chemical N-sulfation to provide N-sulfated analogs of heparin/HS oligosaccharides for testing their activities. Four specific aims are 1) chemical synthesis of N-acetylglucosamine (GlcNAc) and uronic acid derivatives as monosaccharide precursors; 2) synthesis of UDP-GlcNAc, UDP-uronic acids, and their derivatives; 3) enzymatic synthesis of heparin and heparan sulfate oligosaccharide analogs using heparosan synthases; 4) structure-activity relationship (SAR) studies using heparin/heparan sulfate-binding proteins. In addition, we will collaborate with our colleague and long-time collaborator, Prof. Andrew Fisher, an expert structural biologist with special expertise on protein crystal structural studies to solve the crystal structures of heparosan synthases, which are important enzymes for the assembly of heparin/HS polysaccharide structures. The information learned and the products obtained will facilitate the discovery and development of new therapeutics.