Structures of the acidic oligosaccharides isolated from rat sublingual glycoprotein

Alkaline borohydride reductive cleavage of the major glycoprotein fraction of rat sublingual gland resulted in the release of a series of reduced oligosaccharides. Five sialic acid-containing oligosaccharides composed of 9, 10, 12, 13, and 15 sugar residues, respectively, have been purified from the acidic oligosaccharide fraction. The structures of these oligosaccharides, as determined by sequential digestion with specific glycosidases, periodate oxidation and methylation analyses of the native and desialyzed compounds, are proposed to be (formula: see text).