底物工程导向的区域选择性酶法alfa-2,6-唾液酸糖苷化及其应用

天然糖链骨架上半乳糖单元和N-乙酰氨基半乳糖单元的alfa-2,6-唾液酸化是各类糖缀合物和游离糖链的最常见的修饰形式，所生成的alfa-2,6-唾液酸化糖链在细胞间信号传导、相互识别，炎症、肿瘤、病原微生物侵入等生理和病理过程中均发挥着至关重要的作用。本项目以含有多个alfa-2,6-唾液酸化位点底物的区域选择性alfa-2,6-唾液酸化挑战为目标，拟通过将氧化还原体系整合到申请人课题组所发展的糖链酶法模块化组装策略中去，以氧化还原体系来精准控制多唾液酸化位点底物的区域选择性alfa2,6-唾液酸化。这一具有普适性的底物工程策略有望为复杂唾液酸糖链的合成提供了一条简洁、高效、普适性的新途径。由于其它天然单糖也有对应的氧化酶，因而本项目中发展的底物工程策略有望为其它类型复杂糖链的合成提供新的解决途径。

The alfa-2,6-linked sialic acid is one of the most common moieties of various N-glycans, O-glycans, glycolipids and secreted unconjugated glycans. The alfa-2,6-linked sialosides play pivotal roles in modulating and mediating a variety of physiological and pathological processes. Despite different chemical and enzymatical methods are available for the synthesis of simple alfa-2,6-linked sialosides. An efficient method for the synthesis of regioslectively alfa-2,6-sialylated complex glycans is missing. To tackle this problem, we proposed a novel strategy by combining the redox system to our previously developed enzymatic modular assembly system for the precisely controlled synthesis of regioselectively alfa-2,6-sialylated complex sialosides. As the key step in this proposed novel strategy, the galactose oxidase will be used for the oxidize Gal or GalNAc at the unwanted sialylation site to C6-aldehyde-Gal or C6-aldehyde-GalNAc and leave the sialylation site Gal or GalNAc unchanged for enzymatic sialylation.