从绿藻礁膜（Monostroma nitidum Wittr）分离半乳糖专一的凝集素

礁膜（Monostroma nitidum Wittr）经 25%～80%硫酸铵分级、DEAE-纤维素52离子交换层析和Sephadex G-200凝胶过滤层析，得到纯化礁膜凝集素（Monostroma nitidum lectin，MNL），在SDS-PAGE上显示单一蛋白染色带. 用Sephadex G-200层析测得其分子质量为66.6 kD, 用SDS-PAGE测得其分子质量为66.2 kD．该凝集素可以凝集人A、B、AB、O型红细胞，且凝集活性相同. 在对人（A、B、AB、O）、兔、鲤、鲫、鼠、羊、鸡、狗的红细胞凝集作用中，兔凝集作用最强．该凝集素在pH 4.00～10.53范围内均有活性，但在pH 5.20～9.40范围内活性最大．经100 ℃热处理30 min后，该凝集素对兔红细胞血凝活性保留25%，活性最大的温度范围为25～55 ℃．MNL被EDTA抑制，最小抑制浓度为3.13 mmol/L，但对 Ca^２＋和Mg^２＋不敏感．该凝集素凝集兔红细胞的作用不被D -果糖、D-甘露糖、D-葡萄糖、蔗糖、麦芽糖、γ-球蛋白、牛甲状腺球蛋白所抑制，但被D- 半乳糖和乳糖抑制，最小抑制浓度分别为5 mmol/L和2.5 mmol/L．

A Galactose-specific Lectin Isolated from Green Alga Monostroma nitidum Wittr

A Monostroma nitidum Wittr lectin (MNL), was extracted from green alga Monostroma nitidum Wittr by 25%～80% ammonium sulfate fractionation and an ion exchange on DEAE-cellulose 52, and purified by gel filtration on Sephadex G-200. SDS-PAGE showed that the lectin gave a single band at 66.2 kD. Gel filtration of purified lectin on Sephadex G-200 indicated that it existed as a 66.649 kD protein in natural conditions. The MNL was nonspecific in agglutination for any type of human erythrocytes, and the hemagglutination activity was equal. The lectin agglutinated rabbit erythrocytes with the highest titers, among erythrocytes of human (A, B, AB, O), rabbit, common carp, crucian carp，mouse, goat, dog, and chicken. The lectin activity was observed at pH 4.0～10.53, with peak at pH 5.20～9.40. This lectin had the maximum hemagglutination activity at 25～55 ℃,and 25% lectin activity was kept at 100 ℃ for 30 min. The activity was inhibited by EDTA, with the minimum inhibitory concentration of 3.13 mmol/L, but not affected by the Ca^2＋ and Mg^２＋. The hemagglutination activity was not inhibited by D-fructose, D-mannose，D-glucose, sucrose, maltose, gamma globulin (human) and bovine thyroglobulin, but inhibited by D galactose and lactose whose minimum inhibitory concentrations were 5 mmol/L and 2.5 mmol/L, respectively.