Abstract
A sialoglycoprotein (SGP) has been purified from the skin mucus of the stingray Dasyatis akajei. SGP contained 22.1% (w/w) NeuAc, 24.4% GalNAc, 9.9% GlcNAc, 6.1% Gal, and 27% amino acids, and its average molecular weight (Mr) was estimated to be 500, 000. SGP was very rich in Thr (32 mol%) and Ser (12 mol%). Treatment of SGP with alkali (β-elimination of carbohydrate chains) result-ed in the destruction of 70% of Thr and Ser, indicating that the carbohydrate chains were attached through these amino acids. Exhaustive digestion of SGP by actinase yielded a highly glycosylated glycopeptide with Mr of 50, 000. Based on these results, it is assumed that a SGPmolecule bears more than 400 oligosaccharide chains which are attached to the Thr and Ser residues of the polypeptide backbone and spaced at an average of 3 amino acids apart.
