Chemoenzymatic synthesis of bacterial nonulosonic acids and glycans

项目摘要 细菌壬糖酸和聚糖的化学酶法合成 唾液酸是一个广泛分布的壬酮糖酸（具有九个碳骨架的α-酮酸）家族， 脊椎动物和一些致病细菌。细菌还产生非酮糖酸， 在动物身上发现的。这些细菌特异性非酮糖酸已被细菌用作其代谢的一部分。 作为细菌毒力因子的荚膜多糖（CPS）和脂多糖（LPS）， 潜在的疫苗候选人结构定义的细菌CPS、LPS和相应的 寡糖重复单元是研究其在细菌感染和微生物-宿主关系中作用的重要探针 相互作用，包括它们对宿主免疫系统的影响。这些碳水化合物是有吸引力的合成 目标，但构成重大的合成挑战。除了细菌特异性的非酮糖酸外，它们还可以 还含有其他在哺乳动物中未发现的单糖结构单元。的糖苷键 在细菌多糖中发现的多糖也比在哺乳动物聚糖中发现的多糖多样得多。我们提出 开发有效的化学酶法合成细菌壬糖酸及其聚糖， 病原菌的部分CPS和LPS寡糖。这些代表了生物学上的重要性， 具有挑战性的目标。在目前的提案期限内，重点将放在细菌聚糖上 含有军团胺酸及其衍生物。具体目标有三：1、合成受体， 用于一锅多酶（OPME）糖基化系统的单糖化学酶促反应; 2， 鉴定和表征候选糖-1-P激酶、UDP-糖合成酶和糖基转移酶;以及 3、化学酶法合成含有军团菌胺酸或 衍生物.所鉴定的酶和所设计的单糖是重要的工具和试剂， 获得合成的挑战性碳水化合物和糖缀合物， 提案中所述。所产生的寡糖是更好地了解 细菌多糖的重要作用。它们也是合成结构定义的 碳水化合物-蛋白质缀合物疫苗以对抗细菌感染。

Project Summary Chemoenzymatic synthesis of bacterial nonulosonic acids and glycans Sialic acids are a family of wide-spread nonulosonic acids (alpha-keto acids with a nine-carbon backbone) in vertebrates and in some pathogenic bacteria. Bacteria also produce nonulosonic acids that have not been found in animals. These bacterium-specific nonulosonic acids have been used by bacteria as part of their capsular polysaccharides (CPSs) and lipopolysaccharides (LPSs) which are bacterial virulence factors and potential vaccine candidates. Structurally defined bacterial CPSs, LPSs, and the corresponding oligosaccharide repeating units are important probes to study their roles in bacterial infection and microbe-host interaction including their influence on host immune systems. These carbohydrates are attractive synthetic targets but pose significant synthetic challenges. In addition to bacterial specific nonulosonic acids, they may contain other monosaccharide building blocks that have not been found in mammals. The glycosidic linkages found in bacterial polysaccharides are also much more diverse than those in mammalian glycans. We propose to develop efficient chemoenzymatic methods to synthesize bacterial nonulosonic acids and their glycans as part of CPS and LPS oligosaccharides of pathogenic bacteria. These represent biologically important and synthetically challenging targets. In the current proposal duration, the focus will be on bacterial glycans containing legionaminic acid and their derivatives. Three specific aims are: 1, Synthesize acceptors and monosaccharide chemoenzymatic synthons for one-pot multienzyme (OPME) glycosylation systems; 2, Identify and characterize candidate sugar-1-P kinases, UDP-sugar synthetases, and glycosyltransferases; and 3, Chemoenzymatic synthesis of bacterial polysaccharide repeating units containing legionaminic acid or derivatives. The enzymes identified and the monosaccharides designed are important tools and reagents for accessing synthetic challenging carbohydrates and glycoconjugates that are not limited to the targets described in the proposal. The oligosaccharides produced are essential probes for better understanding the important roles of bacterial polysaccharides. They are also candidates for synthesizing structurally defined carbohydrate-protein conjugate vaccines to combat bacterial infections.