Studies on biochemical properties of fish skin-mucus glycoproteins

本研究旨在阐明鱼皮肤粘液糖蛋白的特性。研究人员使用了五种原产于有牙海的鱼类：Mutsugoro、Warasubo、Hazekuchi、Akashitabirame和Shoukihaze，并从活鱼样本中提取鱼皮粘液。用核酸酶消化、热处理、酸处理、离子交换层析、凝胶层析等方法分离皮肤粘液中的糖蛋白。Akashitabirame和Shoukihaze(第I组)的糖蛋白在离子交换层析和凝胶层析上的行为与我们迄今已研究的其他鱼类的糖蛋白几乎相同。然而，Mutsugoro、Warasubo和Hazekuchi(II组)的糖蛋白在两种层析中的表现不同。糖组成分析表明：(1)I组和II组糖蛋白的总糖含量分别为50%~75%和10%左右：(2)I组糖蛋白以NeuAc和GalNAc为主，II组以GlcNAc、Gal、Man、NeuAc为主。甘露糖是N连接糖蛋白的特征，而O连接糖蛋白则不是甘露糖。从鱼粘液中分离的糖蛋白中未检测到甘露糖，I组和II组的糖蛋白分别通过β消除和联氨分解释放出糖链。因此，I组和II组的糖蛋白分别被证实为O-连接和N-连接的糖蛋白。基团I的主要糖链结构相同，鉴定为NeuAcα2-6GalNAc。Mutsugoro的主要糖链结构推测为复合型，由NeuAc、Gal、Man和GlcNAc组成。

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.