Interaction of five d-mannose-specific lectins with a series of synthetic branched trisaccharides

Abstract

The interaction of a series of synthetic, branched trisaccharides with five d-mannose-specific lectins was studied by precipitation-inhibition assay. The branched methyl α- d-mannotrioside, α- d-Man p-(1→3)-[α- d-Man p-(1→6)-α- d-Man pOMe, the best inhibitor of the Con A—Dextran interaction, was 42 times more potent than α- d-Man pOMe, and 3–6 times more potent than the two trisaccharides substituted with d-glucosyl groups, and 8–15 times those with d-galactosyl groups. Surprisingly, methyl O-α- d-mannopyranosyl-(1→3)-α- d-mannopyranoside was bound to Con A 8-fold more avidly than methyl α- d-mannopyranoside. However, the related pea lectin (PSA) was singularly different from Con A in its carbohydrate-binding activity, showing no significantly enhanced binding to any of the sugars examined. The trisaccharides containing terminal, nonreducing, (1→3)-linked α- d-mannopyranosyl groups, i.e., α- d-Man p-(1→3)-[α- d-Glc p-(1→6)-α- d-Man pOMe, α- d-Man p-(1→3)-]α- d-Gal p-(1→6)]-α- d-Man pOMe, and α- d-Man p-(1→3)-[α- d-Man p-(1→6)]-α- d- Man pOMe, were the best inhibitors of the snowdrop lectin (GNA)- d-mannan precipitation system. On the other hand, all branched trisaccharides exhibited very similar inhibitory potencies toward the daffodil lectin (NPA)- d-mannan interaction, whereas α- d-Man p-(1→3)-[α- d-Gal p-(1→6)]-α- d-Man pOMe and α- d-Man p-(1→3)-[α- d-Man p-(1→6)]-α- d-Man pOMe were somewhat better inhibitors than the other branched trisaccharides of the amaryllis lectin (HHA)- d-mannan precipitation reaction. Of the oligosaccharides studied, the linear trisaccharide α- d-Man p-(1→6)-α- d-Man p-(1→6)- d-Man appears to be the most complementary to the combining site(s) of NPA and HHA.