中文摘要：

糖基化作用是真核生物蛋白翻译后修饰的重要环节，糖链对于蛋白质的结构和功能有重要影响。目前，合成带有均一糖链的糖蛋白和糖肽的策略主要有：（1）利用糖基化的氨基酸进行固相或液相合成。（2）将氨基化的寡糖链直接与预先合成的带有糖基化位点的多肽相结合。（3）利用糖基转移酶和糖苷酶的化学酶法合成策略。以上三种方法，都有各自的优点和不足。相对而言，利用微生物来源的B．N．乙酰氨基葡萄糖苷内切酶（ENGase）合成策略是目前发展较快且更具实践意义的方法。糖苷内切酶法合成策略的研究进展包括：（1）ENGase催化机制的研究。（2）糖基供体的研究。（3）ENGase突变体的研究。（4）糖苷内切酶法的应用。

英文摘要：

Protein glyeosylation is the important step involved in post-translational modifications within eukaryotes, and it plays a significant role in protein folding and transportational processes. The oligosaceharide moieties of glycoeonjugates have a major impact on the structure and functions of protein, and influence biological phenomena such as lectin binding, viral infection and cellular recognition. In the field of glycobiology, it is necessary to investigate the homogeneous glycopeptides and glycoprotein for detailed structural and functional studies of glycoproteins. As a result, how to synthesize this kind of glycoprotein and glycopeptides efficiently has become an important subject in glycotechnology. At the present time, three major strategies have been developed to synthesize homogeneous glycopeptides. One is using pre-formed glycosyl amino acids as building blocks in solid-phase or solution-phase peptide synthesis. Another strategy is combining an oligosaccharide glycosylamine with a pre-assembled polypeptide which contains a free or selectively activated aspartyl side chain to synthesize glycoprotein. The main disadvantages of these approaches are that the strong acidic conditions may cause partial hydrolysis of the attached oligosaccharide moiety. To deal with these problems mentioned in the above strategies, a new ehemoenzymatic approach combined with endoglycosidase which from microorganisms to synthesize homogeneous glyeopeptides is developed. This approach requires only monosaccharide-tagged polypeptides, and the reaction condition is very moderate. The sugar chain extension is combined with free polypeptides in aqueous solutions, without the using of protecting groups. Both glyeosyltransferases and endoglyeosidases have been explored for this chemoenzymatic strategy. Compared with glyeosyltransferase-based methods, the endoglyeosidase-based approach is more attractive because it can connect a large intact oligosaccharide to a GleNAc polypeptide in one-step. Although this endoglycosidase-based chemoe