Structure of the monosialyl oligosaccharides derived from salivary gland mucin glycoproteins of the Chinese swiftlet (genus Collocalia). Characterization of novel types of extended core structure, Gal beta(1– –3)[GlcNAc beta(1—-6)] GalNAc alpha(1—-3)GalNAc(-ol), and of chain termination, [Gal alpha(1—-4)]0-1[Gal beta(1—-4)]2GlcNAc beta(1—- .)
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JM Wieruszeski, JC Michalski, J Montreuil, G Strecker, J Peter-Katalinic, H Egge, H van Halbeek, JH Mutsaers and JF Vliegenthart
The mucus glycoproteins, the so-called nest-cementing substance, from the salivary gland of Chinese swiftlets (genus Collocalia) are mainly constituted of sialic acid-rich O-glycosylproteins. Alkaline reductive treatment of the crude material led to the release of some neutral and numerous monosialyl and disialyl oligosaccharides. These were fractionated by gel filtration, anion-exchange chromatography, and high- performance liquid chromatography. The structures of the monosialyl oligosaccharides were established by combination of sugar and methylation analysis, fast atom bombardment-mass spectrometry, and electron impact-mass spectrometry after permethylation and 1H NMR spectroscopy (at 500 MHz). Typically, some of the monosialyl oligosaccharides appeared to possess the core structure Gal beta(1—- 3)[GlcNAc beta(1—-6)]GalNAc alpha(1—-3)GalNAc-ol. Moreover, the (1– –6)-linked branch consisted of an unusual di- or trigalactosyl sequence, [Gal alpha(1—-4)0-1Gal beta(1—-4)Gal beta (1—-4)GlcNAc beta(1—-6). Thus, the most complex representatives of the monosialyl fraction from Collocalia mucin were found to be: (Formula: see text) The other compounds identified are partial structures thereof.
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