蛋白糖基化和糖蛋白去糖基化是互相关联的生物学过程，已知糖基化与肿瘤、感染和免疫疾病相关，但受研究方法和技术手段限制，糖蛋白去糖基化的研究尚在起步中。去糖基化主要由糖苷酶介导，其中N-糖苷酶水解N-糖蛋白释放完整糖链，既是重要的功能酶，如人N-糖苷酶NGLY1与神经病变和智力障碍相关，也是重要的工具酶，如PNGase F用于N-糖蛋白结构和功能研究，但这两个酶对有核心α-1,3岩藻糖N-糖蛋白不敏感。我们前期在脑膜炎败血伊丽莎白金菌中发现了一种新型N-糖苷酶，对核心α-1,3岩藻糖N-糖蛋白有去糖基化作用，解析了晶体结构，命名为Ⅱ型 N-糖苷酶PNGase F-Ⅱ(发表于JBC，2015)。本项目采用质谱分析和共结晶技术，拟开展PNGase F-Ⅱ底物的特征性分析、酶活性位点及PNGase F-Ⅱ/底物复合物晶体结构的研究，以阐明该酶的催化机制，为核心α-1,3岩藻糖的糖生物学研究奠定基础。

Protein glycosylation and deglycosylation of glycoproteins are two important biological reactions. Although studies have shown that glycosylation is associated with cancer, infections and immune diseases, research on deglycosylation is still underway for the limited technology and methods. Deglycosylation is mainly mediated through Peptide:N-glycosidase (PNGase), which cut intact asparagine-linked oligosaccharide chains from N-glycoproteins. PNGase is playing a key role in biological process (such as human PNGase (NGLY1)) and in glycobiology research as well (PNGase F). However, one common limitation of both NGLY1 and PNGase F is insensitive to glycans with core α-1,3 fucose on N-glycoprotein. Recently, we identified a novel PNGase from a clinical isolate of Elizabethkingia meningoseptica that could cleave the intact asparagine-linked oligosaccharide chains from core α-1,3 fucosylated N-glycoprotein (Published in JBC, 2015, Patent Application No. 201410134277.3). It was named as PNGase F-Ⅱor type 2 PNGase F. As a continuation of the previous work, we plan to illustrate the crystal structure of PNGase F-Ⅱ/substrate complex, and to identify the active sites of the enzyme. The study will establish the mechanism for its action and regulation, and to provide an alternative tool with a unique feature for the understandings of the deglycosylation of N-glycoproteins with core α-1,3 fucose.