Endo-β- N-acetylglucosaminidase-catalyzed polymerization of β-Glc p-(1→4)-Glc pNAc oxazoline: a revisit to enzymatic transglycosylation

Abstract

An alternative synthesis of β-Glc p-(1→4)-Glc pNAc oxazoline is described, and its enzymatic reaction with the endo-β- N-acetylglucosaminidase from Arthrobacter protophormiae (Endo-A) was re-investigated. Under normal transglycosylation conditions with a catalytic amount of enzyme, Endo-A showed only marginal activity for transglycosylation with the disaccharide oxazoline, consistent with our previous observations. However, when used in a relatively large quantity, Endo-A could promote the transglycosylation of the disaccharide oxazoline to a Glc pNAc-Asn acceptor. In addition to the initial transglycosylation product, a series of large oligosaccharides were also formed due to the tandem transglycosylation to the terminal glucose residues in the intermediate products. In the absence of an external acceptor, Endo-A could polymerize the disaccharide oxazoline to form oligo- and polysaccharides having the -4-β-(Glc p-(1→4)-β −Glc pNAc)-1—repeating units. This is the first example of an endo-β- N-acetylglucosaminidase-promoted polymerization of activated oligosaccharide substrates. This enzymatic polymerization may find useful applications for the synthesis of novel artificial polysaccharides.