Structure Determination of Oligosaccharides Isolated from A+, H+ and A-H- Hog-Submaxillary-Gland Mucin Glyoproteins, by 360-MHz 1H-NMR Spectroscopy, Permethylation Analysis and Mass Spectrometry

Abstract

Alkaline borohydride, reductive cleavage (β-elimination) of hog submaxillary glycoproteins from three immunologically determined phenotypes, viz. A⁺, H⁺ and A⁻H⁻, resulted in the release of a series of neutral and acidic oligosaccharide-alditols. 360-MHz ¹H-NMR spectroscopy in combination with methylation analysis and mass spectrometry were used for reinvestigation of the structures of these oligosaccharide-alditols. All are partial structures representing the possible complete and biosynthetically incomplete stages of the chain of a pentasaccharide-N-acetylgalactosaminitol, present in the glycoprotein with blood-group-A activity: In this way, a prolonged argument about the occurrence of a NeuGc(α2 → 6)Gal moiety in these carbohydrate chains, suggested by Aminoff et al. [Aminoff, D., Baig, M. M. and Gathmann, W. D. (1979) J. Biol. Chem. 254, 1788–1793 and 8909–8913] has been brought to a definite end. In the investigated oligosaccharide-alditols N-glycoloylneuraminic acid (NeuGc) is in no case attached to galactose (Gal), but, if present, it is (α2 → 6)-linked to N-acetylgalactosaminitol (GalNAc-ol).