Characterisation of oligosaccharides released from human-blood-group O erythrocyte glycopeptides by the endo-beta-galactosidase of Bacteroides fragilis. A study of the enzyme susceptibility of branched poly(N-acetyllactosamine) structures

Abstract

Desialylated human blood group O erythrocyte glycopeptides were digested with the endo-beta-galactosidase of Bacteroides fragilis and the enzyme-released products reduced with NaBH4 and purified by Bio-Gel P-4 chromatography. Three linear and six branched oligosaccharides of poly(N-acetylllactosamine) type, which together accounted for 90% of the oligosaccharide alditols, were characterised by fast-atom-bombardment mass spectrometry and gas-liquid chromatography/mass spectrometry. Linkage and composition data were obtained for the remaining material. The salient findings were (a) the branched oligosaccharide alditols each contained the sequence: (Formula: see text) and (b) there was no evidence for the terminal branch-point sequence: (Formula: see text). Together these observations indicate that, as with erythrocyte glycolipids described previously [Scudder, P., Hanfland, P., Uemura, K. & Feizi, T. (1984) J. Biol. Chem. 259, 6586-6592], the endo-beta-galactosidase of Bacteroides fragilis cannot hydrolyse branch-point beta-galactosidic linkages on erythrocyte membrane glycopeptides.