New chemoenzymatic methods for synthesizing complex carbohydrates

在此输入文本，它是应用程序的新摘要信息。此部分不得超过30行 短信了 复杂碳水化合物在生物系统中起着重要作用。然而，要获得这些非常困难。 通过从自然界中分离或化学合成，以纯均质形式形成结构。因此 详细的结构-活性关系通常不清楚，即使对于具有重要意义的已知化合物， 功能协调发展的本项目的最终目标是开发新的化学酶合成方法， 以足够大的量获得具有合成挑战性的碳水化合物和类似物， 表征、功能研究和治疗应用。在目前的融资期内，我们 专注于肝素和硫酸乙酰肝素（HS）寡糖类似物的合成。 我们假设N-硫酸化类似物可以模拟肝素/HS寡糖与其靶点结合 蛋白质，具有相似的生物活性。此外，具有合成可控的N-硫酸化类似物， 硫酸化模式可以是探测单个硫酸化的重要作用并提供关键的 关于功能性肝素/HS寡糖中相关O-硫酸化的个体作用的信息。为了验证这一 假设，我们建议合成一系列N3-修饰的GlcNAc或GlcA衍生物，其可用作 UDP-GlcNAc和UDP-GlcA生物合成酶和肝素原酶的底物，用于产生N3- 含有低聚糖。叠氮基然后可以被还原成氨基，然后被还原成氨基。 化学N-硫酸化以提供肝素/HS寡糖的N-硫酸化类似物用于测试它们的活性。 四个具体目标是：1）化学合成N-乙酰葡糖胺（GlcNAc）和糖醛酸衍生物， 单糖前体; 2）UDP-GlcNAc、UDP-糖醛酸及其衍生物的合成; 3） 使用肝素原酶酶促合成肝素和硫酸乙酰肝素寡糖类似物; 4） 使用肝素/硫酸乙酰肝素结合蛋白的结构-活性关系（SAR）研究。此外，我们将 与我们的同事和长期合作者，安德鲁费舍尔教授，专家结构生物学家合作 具有蛋白质晶体结构研究的特殊专长，可解决肝素原的晶体结构 肝素酶是组装肝素/HS多糖结构的重要酶。的 所学到的信息和所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.