Spacer-modified trisaccharide glycosides that mimic the biantennary Asn-linked oligosaccharide acceptor of (1 → 4)-β- d-galactosyltransferase and can be used as competitive inhibitors and for irreversible deactivation

Abstract

The biantennary spacer-modified trisaccharide glycoside methyl 3,6-di- O-(2-acetamido-2-deoxy-β- d-glucopyranosyloxyethyl-α- d- mannopyranoside ( 5) was synthesised and used together with several 2-acylamino-2-deoxy- d-glucose derivatives in competition experiments with β- d-galactosyltransferase. Compound 5 was an acceptor substrate ( K M 0.18 mM) comparable to the biantennary core heptasaccharide of glycoproteins ( K M 0.13 mM). Replacing the N-acetyl group by other N-acyl groups did not alter the kinetic parameters significantly. When the N-acyl group was iodoacetyl, the compound was an irreversible inhibitor.