新型O-甘露聚糖的多样化合成与功能研究

The past few years have witnessed significant advances in glycomics and glycoproteomics, which allowed rapid identification of O-mannosylated proteins and elucidation of O-mannose glycan structures. So far, more than 50 mammalian O-mannosylated proteins have been identified, and more than 20 O-mannose glycan structures have been well characterized, and it is estimated that the O-mannose glycans account for up to 30% of all O-glycans in mammalian brain tissue. Although the biological significance of O-mannose glycans has been well documented, the biosynthetic pathway and the precise function of this diverse glycan library remain unclear. Therefore, the synthesis of structurally well-defined O-mannose glycans in sufficient amount will not only provide carbohydrate standards for the identification of these glycans from natural sources, but also provide the probes for the elucidation of their biosynthetic pathway and structure-activity relationship (SAR) of O-mannose glycans binding to their various receptors. . Three specific aims for this project are 1) Rational design and chemical or chemoenzymatic synthesis 4 O-mannose core structures as acceptors for further sugar chain elongation. 2) Diversity-oriented enzymatic synthesis of all 72 possible Core M1 and Core M2 O-mannose glycans. 3) Structure-activity relationship (SAR) studies of O-mannose glycans with their different receptors.

O-甘露糖基化是近年来在哺乳动物中新发现的一类广泛存的蛋白质修饰形式。O-甘露糖基化在许多生命过程中发挥着至关重要的作用，其糖链生物合成的异常会引起各种类型的先天性肌营养不良症，并能介导肿瘤的转移和病毒的入侵等。O-甘露聚糖及其蛋白聚糖研究是糖生物学研究的热点和前沿领域，由于其结构的多样性和复杂性，O-甘露聚糖的合成研究却远远滞后。本项目拟运用化学酶法合成途径解决O-甘露聚糖的大量获得性问题，在国际上首次对O-甘露聚糖生物合成途径中所有72个可能结构进行系统性、多样化、制备级合成；拟运用微阵列高通量筛选对所得到的O-甘露聚糖库与受体分子进行初步的构效关系研究。O-甘露聚糖的系统性高效合成，对于阐明其生物合成途径，在分子水平上揭示其作用机制，以及发展相关疾病的诊断与治疗方法均具有重要意义。

O-甘露聚糖占人脑组织中O-聚糖的30%以上，其在先天性肌营养不良症，受损神经修复，以及肿瘤的转移和病毒的入侵等生命过程中均发挥着至关重要的作用。然而，由于O-甘露聚糖结构上的复杂性，该系列糖链的合成一直以来是糖链合成领域的一大挑战。在本项目中，我们从微生物中发掘和筛选了系列糖基转移酶，构建了5个糖链组装生物合成元件，发展了酶法模块化组装策略，通过串联的酶法模块化组装，在国际上首次完成了92个复杂O-甘露聚糖的系统性合成。通过与国外同行进行合作，运用糖芯片，对所合成的糖链与糖链受体的结合特点与作用机制进行了初步探究。相关工作发表在JACS，Angew Chem等国际知名期刊上。本项目所合成的系列糖链为系统深入的研究O-甘露聚糖的生物合成机制及其生物学功能奠定了坚实的基础。