Purification and further characterization of a glycoprotein from the skin mucus of Japanese eels

A glycoprotein (EGP) was purified from the skin mucus of Japanese eel Anguilla japonica. Apparent average molecular mass of the EGP was estimated to be 500 000. The EGP was found to contain 30� 8% NeuAc, 26� 4% GalNAc, 6� 4% Gal, 0� 4% NeuGc and 25� 1% Thr-rich protein. EGP was treated with alkaline borohydride for the release of carbohydrate chains (oligosaccharide alditols). Three carbohydrate chains were isolated from the released carbohydrate chains by Sephadex G-25 (superfine) gel filtration and HPLC. Using 1 H-NMR spectroscopy, methylation analysis and glycosidase digestion, the structures of the three carbohydrate chains were determined to be NeuAca2!6GalNAc-ol, NeuAca2!3GalNAc-ol and NeuAca2!6(GalNAca1!3)GalNAc-ol. An overall structure for the sialoglycoprotein from the skin mucus is proposed: the molecule is considered to consist of highly glycosylated 10 glycopeptide units (containing >40 carbohydrate chains) that are linked to the hydroxyl amino acids and spaced on average two amino acids apart. # 2004 The Fisheries Society of the British Isles