Structures of the N-linked oligosaccharides on human plasma vitronectin

The structures of N-linked oligosaccharides present on human plasma vitronectin were elucidated. Oligosaccharides were released from the vitronectin by N-glycosidase F digestion and tagged with 2-aminopyridine; the pyridylamino-oligosaccharides were then fractionated by anion-exchange and reverse-phase HPLC. Ten major pyridylamino-oligosaccharides were isolated. The linkages and locations of sialic acid residues were determined by desialylation with Salmonella sialidase in combination with acid. The asialo forms were then analyzed by two-dimensional sugar mapping, component sugar analysis and 400-MHz 1H-NMR spectroscopy. The major oligosaccharides of human vitronectin were of the diantennary N-acetyllactosamine type, with a lesser amount of the tri- and a small amount of the mono-antennary type, to which 1-3 mol sialic acid residues were linked, mostly through alpha 2-6 linkages, although alpha 2-3 linkages were also present. The possibility that several binding activities of vitronectin can be ascribed to its glycan moiety was discussed, based on the specific features of the N-linked oligosaccharides on human vitronectin revealed here.