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

Abstract

The interaction of a series of synthetic, branched trisaccharides with five -mannose-specific lectins was studied by precipitation-inhibition assay. The branched methyl [alpha]--mannotrioside, [alpha]--Manp-(1-->3)-[[alpha]--Manp-(1-->6)-[alpha]--ManpOMe, the best inhibitor of the Con A--Dextran interaction, was 42 times more potent than [alpha]--ManpOMe, and 3-6 times more potent than the two trisaccharides substituted with -glucosyl groups, and 8-15 times those with -galactosyl groups. Surprisingly, methyl O-[alpha]--mannopyranosyl-(1-->3)-[alpha]--mannopyranoside was bound to Con A 8-fold more avidly than methyl [alpha]--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 [alpha]--mannopyranosyl groups, i.e., [alpha]--Manp-(1-->3)-[[alpha]--Glcp-(1-->6)-[alpha]--ManpOMe, [alpha]--Manp-(1-->3)-][alpha]--Galp-(1-->6)]-[alpha]--ManpOMe, and [alpha]--Manp-(1-->3)-[[alpha]--Manp-(1-->6)]-[alpha]-- ManpOMe, were the best inhibitors of the snowdrop lectin (GNA)--mannan precipitation system. On the other hand, all branched trisaccharides exhibited very similar inhibitory potencies toward the daffodil lectin (NPA)--mannan interaction, whereas [alpha]--Manp-(1-->3)-[[alpha]--Galp-(1-->6)]-[alpha]--ManpOMe and [alpha]--Manp-(1-->3)-[[alpha]--Manp-(1-->6)]-[alpha]--ManpOMe were somewhat better inhibitors than the other branched trisaccharides of the amaryllis lectin (HHA)--mannan precipitation reaction. Of the oligosaccharides studied, the linear trisaccharide [alpha]--Manp-(1-->6)-[alpha]--Manp-(1-->6)--Man appears to be the most complementary to the combining site(s) of NPA and HHA.