Structures of the N‐linked oligosaccharides on porcine plasma vitronectin

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Abstract
The structures of N-linked oligosaccharides, especially the distribution of sialic acid species, present on porcine plasma vitronectin were elucidated. Oligosaccharides were released from the vitronectin by N-glycosidase F digestion and tagged with 2-aminopyridine, and the pyridylamino-oligosaccharides were fractionated by anion-exchange and reverse-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 combination with acid desialylation. After desialylation, the asialo-forms were analyzed by two-dimensional sugar mapping, component sugar analysis and 400-MHz 1H-NMR spectroscopy. The major oligosaccharides of porcine vitronectin were of the fucosylated biantennary type, with a small amount of the triantennary N-acetyllactosamine type, to which 1–3 mol sialic acids was linked. Sialic acids were linked predominantly through α2–6 linkages, although α2–3 linkages were also present, and fucose was linked to the innermost N-acetylglucosamine through an α1–6 linkage. It was found that every pyridylamino-oligosaccharide population contained N-glycolylneuraminic acid and N-acetylneuraminic acid in a molar ratio of 1:2–9, and that N-glycolylneuraminic acids were located predominantly on the Man α1–6 arm.

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