文蛤(Meretrix Meretrix)凝集素(MML)的初步研究——Ⅱ.MML的分子组成及性质鉴定

The Preliminary Studies on the Lectin (MML) from Sea Clam (Meretrix Meretrix) Ⅲ. The molecular composition and the characterization of MML

文蛤凝集素(MML)经实验证明是一种唾液酸专一性结合的凝集素,MML的活力表现依赖于Ca^(2+)。MML对高于40℃以上的温度敏感,其活力在?pH5.0～8.5的范围内稳定。等电聚焦电泳测出MML的等电点是5.6.在12％胶浓度的SDS-PAGE上,用含或不含-S-S-还原剂的样品处理液进行电泳,以及用4％～30％线性梯度胶浓度的PAGE分析,所得结果推测MML分子是由分子量为29000和30000道尔顿的2条肽链组成,肚链间经-S-S-共价联系形成约59000道尔顿的大亚基,再由约18个这种大亚基聚合成1060000道尔顿的MML大分子。氨基酸组成及共价结合糖含量测定表明,MML分子是一种含5％的糖类的糖蛋白。初步观察到MML对人体癌变淋巴母细胞株(Raji细胞)的生长有抑制或杀伤作用。

MML is a sialic acid binding lectin. The lowest concentration of N-acetyln-urominic acid which can inhibit human RBC agglutination activity of MML is 35m-mol/L. MML widely agglutinates every kinds RBC from different animals tested in the experiment. MML can also cause the agglutination of E, coli K_(12) cells. As a Ca^(2+) dependent lectin MML is sensitive to the temperature over 40℃ and to the pH over 8. 5 or below 5. 0. On rod gel IEF MML can be focused as one band with an appearance pI 5. 6. On plate SDS-PAGE of MML if adding -S-S- reductant to the sample buffer two bands separately with MW 29kd and 30kd can be seen, if not adding -S-S-reductant to the sample buffer one main band with MW 59kd and several little coloured bands with MW larger than 59kd can be seen. So we conclu-de that these two kinds of subunit of MML are naturally connected by -S-S--. Onplate pore gredient PAGE MML exhibits one band with MW 1 060kd. In this pap-er, the amino acid composition analysis result and the sugar percentage analysis result of MML were reported. As the first time among the lectins which are sialic aicd binding specificity, this paper also reported that MML has the ability of inhibiting or even killing cancer cells-human malignant lymphoblast (Raji cells).