A novel disaccharide substrate having 1,2-oxazoline moiety for detection of transglycosylating activity of endoglycosidases

A disaccharide substrate of Man beta1-4GIcNAc-oxazoline 2 was designed and synthesized as a novel probe for detection of the transglycosylating activity of endoglycosidases. A regio- and stereoselective transglycosylation reaction of 2 to GlcNAc beta1-O-pNP or DrisAsn(GlcNAc)-OH catalyzed by endo-beta -N-acetylglucosaminidase from Mucor hiemalis (Endo-M) and endo-beta -N-acetylglucosaminidase from Arthrobacter protophormiae (Endo-A) has been demonstrated for the first time, resulting in the core trisaccharide derivative Man beta 4GlcNAc beta1-4GlcNAc beta1-O-pNP 8 (or -(Dns)Asn-OH). Interestingly, the transglycosylation proceeds irreversibly; the resulting trisaccharide 8 was not hydrolyzed by Endo-M and Endo-A. Based on these results, a new mechanism including an oxazolinium ion intermediate has been proposed for the endoglycosidase-catalyzed hydrolysis or transglycosylation. (C) 2001 Elsevier Science BY. All rights reserved.