Structural analysis of O-glycosidic type of sialyloligosaccharide-alditols derived from urinary glycopeptides of a sialidosis patient

Abstract

Sialidosis urine was fractionated by gel filtration on Bio-Gel P-6. All pooled fractions containing carbohydrates showed the presence of small amounts of GalNAc in non-reducing position, besides free N-acetyllactosamine type of oligosaccharides as major constituents. The fractions were subjected to reductive alkaline borohydride degradation, after which the major part of GalNAc was recovered as N-acetyl-D-galactosaminitol (GalNAc-ol). The GalNAc-ol-containing material was separated from the N-glycosidic oligosaccharides by a second gel-filtration step on AcA 202. Subsequently, the O-glycosidic sialyloligosaccharide-alditols were subfractionated by anion-exchange chromatography on Mono Q. Structural analysis by 500-MHz 1H-NMR spectroscopy revealed two major components in all fractions, namely: NeuAc alpha 2-3Gal beta 1-3GalNAc-ol and NeuAc alpha 2-3Gal beta 1-3[NeuAc alpha 2-6]GalNAc-ol. Furthermore, NeuAc alpha 2-3Gal beta 1-3[NeuAc alpha 2-3Gal beta 1-4GlcNAc beta 1-6]GalNAc-ol was found as a minor component in some of the fractions. The presence of these carbohydrate chains in Bio-Gel fractions differing in molecular mass suggested that they are derived from glycopeptides which are heterogeneous in their peptide part.