STRUCTURES OF THE N-LINKED OLIGOSACCHARIDES ON PORCINE PLASMA VITRONECTIN

The structures of N-linked oligosaccharides, especially the distributi on of sialic acid species, present on porcine plasma vitronectin were elucidated. Oligosaccharides were released from the vitronectin by N-g lycosidase F digestion and tagged with 2-aminopyridine, and the pyridy lamino-oligosaccharides were fractionated by anion-exchange and revers e-phase HPLC. Nine major pyridylamino-oligosaccharides were isolated. The linkages and locations of sialic acids were determined by a novel approach involving desialylation with Salmonella sialidase in combinat ion with acid desialylation. After desialylation, the asialo-forms wer e analyzed by two-dimensional sugar mapping, component sugar analysis and 400-MHz H-1-NMR spectroscopy. The major oligosaccharides of porcin e vitronectin were of the fucosylated biantennary type, with a small a mount of the triantennary N-acetyllactosamine type, to which 1-3 mol s ialic acids was linked. Sialic acids were linked predominantly through alpha2-6 linkages, although alpha2-3 linkages were also present, and fucose was linked to the innermost N-acetylglucosamine through an alph a1-6 linkage. It was found that every pyridylamino-oligosaccharide pop ulation contained N-glycolylneuraminic acid and N-acetylneuraminic aci d in a molar ratio of 1:2-9, and that N-glycolylneuraminic acids were located predominantly on the Man alpha1-6 arm.