Glycosylation differences between pig gastric mucin populations: A comparative study of the neutral oligosaccharides using mass spectrometry

Five mucin populations were isolated from the cardiac region, corpus and antrum of pig gastric mucosa. The released neutral oligosaccharides were permethylated and analysed using high-temperature gas chromatography-mass spectrometry (GC-MS) as well as matrix-assisted laser-desorption mass spectrometry (MALDI-MS). Thirty different oligosaccharides with up to six monosaccharide residues were characterized using both techniques, but the presence of an additional 49 structures was suggested on the basis of their molecular mass by MALDI-MS. Oligosaccharides based on core-1 (Gal beta 1-3GalNAc alpha 1-) and core-2 [Gal beta 1-3(GlcNAc beta 1-6)GalNAc alpha 1-] structures were widely distributed, whereas core-3 structures (GlcNA beta 1-3GalNAc alpha 1-) were present only in mucins from the cardiac region and corpus, and core-4 structures [GlcNAc beta 1-3(GlcNAc beta 1-6)GalNAc alpha 1-] were present exclusively in mucins from the cardiac region. Furthermore the oligosaccharides from one of the mucins from the corpus were significantly longer than those from the other populations. The results illustrate vast structural diversity, but the relative abundances show only a few dominating structures, suggesting that many oligosaccharides may be quite rare in pig gastric mucins. Well-defined mucin populations with distinctly different glycosylation can thus be identified in pig stomach, suggesting that glycosylation of the large secreted mucins from this tissue is not a random event.