Title : The structure of
the carbohydrate units of human plasma
galactoglycoprotein determined by 500-megahertz 1H NMR spectroscopy
Abstract :
- Human plasma galactoglycoprotein (Mr = 81,000) which was recently identified and characterized (Schmid, K., Mao, S. K. Y., Kimura, A., Hayashi, S., and Binette , J. P. (1980) J. Biol
- Chem
- 255, 3221-3226) was found to possess an unusually high carbohydrate content (76%) comprised of NeuAc, Gal, Man, Fuc, GalNAc, and GlcNAc.
- The aim of the present investigation was to elucidate the primary structure of the oligosaccharide units of this protein
- For the study of the O-glycosidic oligosaccharide chains , the protein was subjected to beta-elimination and the resulting oligosaccharide preparations were analyzed by 500-MHz 1H NMR spectroscopy
- The structure of the predominant glycan, a hexasaccharide: (formula; see text) and that of a tetrasaccharide: NeuAc alpha(2----3)Gal beta(1----3)[NeuAc alpha (2----6)]GalNAc-ol, were determined
- The protein possesses approximately 40 hexasaccharides and 3 tetrasaccharides/mol.
- For the isolation of its N-glycosidic oligosaccharide chains , the protein was exhaustively digested with proteases followed by chromatography of the desialyzed resulting glycopeptide fraction on concanavalin A-Sepharose
- 500-MHz 1H NMR spectroscopy of the obtained preparations revealed the presence of 3 diantennary N-glycosidic chains that are extended with a Fuc residue at the Asn-linked GlcNAc. residue at the Asn-linked GlcNAc