Arthrobacter endo-beta-N-acetylglucosaminidase shows transglycosylation activity on complex-type N-glycan oxazolines: one-pot conversion of ribonuclease B to sialylated ribonuclease C.

Asparagine-linked glycosylation is a major form of posttranslational modifications, which plays important roles in protein folding, intracellular signaling, and a number of other biological recognition events . Glycoproteins are often characterized by their structural micro-heterogeneity where different glycoforms have the same polypeptide backbone but differ in the pendant oligosaccharides. Of particular interest are the findings that subtle difference in the attached glycans can have a significant impact on the biological functions of a given glycoprotein . The urgent need of pure glycoforms for functional studies and biomedical applications has stimulated a great interest in exploring new methods for making homogeneous glycoproteins . Major advances include the application of native chemical ligation and expressed protein ligation for constructing full-size glycoproteins , chemoselective ligation to introduce homogeneous glycans , and the engineering of yeast glycosylation pathways to produce single glycoforms . Yet another interesting advance in the field is the endoglycosidase-catalyzed transglycosylation for glycosylation engineering and glycoprotein synthesis .