野花生豆凝集素寡糖链的结构研究

Structural Studies of the Oligosaccharides of Crotalaria Mucronata Lectin

为了探讨凝集素的分子识别机制，对Ａ型血专一性凝集素———野花生豆凝集素的寡糖链结构进行了研究。纯化的野花生豆凝集素（ＣＭＬ）用肼解法释放出肽链上的寡糖链，经离子交换层析和纸层析去除肽链和其它小分子物质后，再用ＮａＢＨ４还原寡糖链的还原末端残基，经ＢｉｏＧｅｌＰ４凝胶柱过滤可分离出ＣＭＬ分子上的４个主要寡糖链。将其分别进行甲醇解反应，最后制成三甲基硅醚衍生物，用气相色谱法分析其糖基组成。结果表明，ＣＭＬ分子中含４种寡糖链，其糖基组成分别为，寡糖Ⅰ：Ｇａｌ８Ｇｌｃ５ＧａｌＮＡｃ２，寡糖Ⅱ：Ｇａｌ４Ｇｌｃ３ＧａｌＮＡｃ２，寡糖Ⅲ：Ｍａｎ２Ｇａｌ６Ｇｌｃ４ＧａｌＮＡｃ２ＧｌｃＮＡｃ２，寡糖Ⅳ：Ｍａｎ２Ｇａｌ６Ｇｌｃ４ＧａｌＮＡｃ２。

The structures of oligosaccharides from crotalaria mucronata lectin(CML) with human A blood group specificity were studied to elucidate the molecular recognition mechanism of lectin.Hydrazinolysis was used for releasing the Aspargine linked sugar chains from the purified CML,ion exchange and paper chromatography for removing the peptides and lower molecular portion.The oligosaccharides were then reduced by NaBH 4 to obtain oligosaccharides with N acetylamin oglucositol at the reducting end,which could be fractionated by passing through a Bio gel P 4 column,and four oligosaccharides could be separated.These four portions were methanolysed and finally transformed into derivatives of trimethylsilane.At last,gas chromatography of these four derivatives showed that these four oligosaccharides were Gal 8Glc 5GalNAc 2,Gal 4Glc 3GalNAc 2,Man 2Gal 5GalNAc 2GlcNAc 2 and Man 2Gal 5Glc 4GalNAc 2.