Studies on biochemical properties of fish skin-mucus glycoproteins

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This research was conducted to clarify the characteristics of fish skin-mucus glycoproteins. Five kinds of fish species that are indigenous to Ariake Sea, Mutsugoro, Warasubo, Hazekuchi, Akashitabirame, and Shoukihaze, were used for fish samples.Fish skin-mucus was prepared from live fish samples. Glycoproteins in the skin-mucus were separated by Nuclease digestion, heat treatment, acid treatment, ion-exchange chromatography, and gel chromatography. Chromatographic behaviors on both ion-exchange and gel chromatographies of glycoproteins from Akashitabirame and Shoukihaze (the group I) was almost identical to those of glycoproteins from other fish species we had already studied so far. However, glycoproteins from Mutsugoro, Warasubo, and Hazekuchi (the group II) did not behaved similarly in both chromatographies.Sugar compositional analysis of these glycoproteins revealed that : (1)total sugar contents of glycoproteins from the groups I and II were 50-75% and around 10%, respectively : (2)NeuAc and GalNAc were found dominantly in the group I, and GlcNAc,Gal,Man,NeuAc were found in the group II. Mannose is characteristic for N-linked glycoproteins but not for O-linked glycoproteins. Mannose had not been detected in glycoproteins isolated from fish mucus.Sugar chains of the glycoproteins could be released by β-elimination and hydrazinolysis for the groups I and II, respectively. Therefore, glycoproteins from the groups I and II were confirmed to be O-linked and N-linked glycoproteins, respectively. Structure of major sugar chain from the group I was identical, and was identified to be NeuAcα2-6GalNAc. On other hand, structure of the major sugar chain from Mutsugoro (the group II) was presumed to be the complex type, which was composed of NeuAc,Gal,Man,and GlcNAc.