The Amazing Transglycosylation Activity of Endo-β-N-acetylglucosaminidases

Abstract

Major advances have been made in exploring the transglycosylation activity of endo-β-N-acetylglucosaminidases (ENGases) for synthetic purpose. The exploration of synthetic sugar oxazolines as donor substrates for the ENGase-catalyzed transglycosylation has expanded the substrate availability and significantly enhanced the overall transglycosylation efficiency. On the other hand, site-directed mutagenesis in combination with activity screening has led to the discovery of the first generation ENGase-based glycosynthases that can use highly active sugar oxazolines as substrates for transglycosylation but lack hydrolytic activity on the ground-state products. ENGases have shown amazing flexibility in transglycosylation and possess much broader substrate specificity than previously thought. Now the ENGase-based chemoenzymatic method has been extended to the synthesis of a range of complex carbohydrates, including homogeneous glycopeptides, glycoproteins carrying well-defined glycans, novel oligosaccharide clusters, unusually glycosylated natural products, and even polysaccharides. This article highlights recent advances related to ENGase-catalyzed transglycosylation with a focus on their synthetic potential.

Keywords: chemoenzymatic synthesis; endoglycosidase; glycoprotein; sugar oxazoline; transglycosylation.

Figure 1

ENGase-catalyzed hydrolysis and transglycosylation

Figure 2

Glyco-engineering of human IgG1-Fc

Figure 3

Transglycosylation by glycosynthase mutant EndoM-N175A

Scheme 1

Synthesis of Man₆GlcNAc-oxazoline and its reaction with Endo-A

Scheme 2

Transglycosylation with the tetrasacharide oxazoline by Endo-A

Scheme 3

Endo-M catalyzed transglycosylation with modified sugar oxazolines

Scheme 4

ENGase-catalyzed transglycosylation for N-glycoprotein synthesis

Scheme 5

Catalytic 1,3-dipolar cycloaddition to introduce αGal epitope into RNase

Scheme 6

A combined method for producing homogeneous glycoprotein

Scheme 7

Enzymatic introduction of N-glycans into natural products by Endo A

Scheme 8

Endo-A catalyzed tandem transglycosylation

Scheme 9

Chemoenzymatic synthesis of novel N-glycan clusters

Scheme 10

Endo-A catalyzed transglycosylation with complex type N-glycan oxazoline