Glycotechnological Studies on Oligosaccharide Units Involved in Molecular Recognition.

目前，人们对开发与糖共轭有关的低聚糖的合成路线非常感兴趣。通过糖苷酶介导的糖基化反应，我们建立了三条参与糖共轭的二糖和三糖的合成路线。首先，甘露三糖和N，N‘-二乙酰基壳二糖利用黑曲霉的β-D-甘露聚糖酶选择性地合成了甘露三糖和N，N’-二乙酰基壳二糖，甘露糖是大多数N-糖蛋白核心区的共同结构特征。其次，利用猪睾丸β-D-半乳糖苷酶介导的糖基化反应，以乳糖和对-硝基-N-乙酰氨基半乳糖为原料，区域选择性地合成了粘蛋白型碳水化合物模拟单位Galbeta1-3GalNAcalpha-OC_6H_4NO_2-p。最后，利用诺卡氏菌的β-N-乙酰氨基己糖苷酶，通过N-乙酰氨基转移，合成了神经鞘糖脂中常见的三糖单元--内酯-N-三糖II糖苷及其两个β-(1-6)连接的异构体。在这种情况下，当使用对硝基苯基乳糖苷受体与β-环糊精的包合物时，糖苷酶催化形成三糖糖苷的区域选择性发生了实质性的变化。这不仅显著提高了转移产物的总收率，而且还增加了所需化合物(GlcNAcbeta1-3Galbeta1-4Glcbeta-OC_6H_4NO_2-p).的比例此外，还合成了含有一系列β-半乳糖基二糖的糖共聚物，并将其作为寡糖-凝集素相互作用分析的模型。通过双扩散试验和凝集素血凝活性抑制实验研究了它们与不同凝集素的相互作用。这些水溶性糖共聚物被证明是一种有用的工具，作为碳酸盐识别的探针。

There is high currentinterest in developing synthetic routes to oligosaccharides involved in glycoconjugates. We established three synthetic routes of di- and trisaccharides, which are involved in glycoconjugate, through glycosidase-mediated transglycosylation. These synthetic oligosaccharides would be used for preparing glycopolymer as probes in carbohydrate-protein interaction studies.Firstly, Manbeta1-4GlcNAcbeta1-4GlcNAc, which is the common structural feature at the core region of most of the N-glycoproteins, was regioselectively synthesized from mannotriose and N,N'-diacetylchitobiose utilizing beta-D-mannanase from Aspergillus niger. Secondary, Galbeta1-3GalNAcalpha-OC_6H_4NO_2-p, which is a mimic unit at carbohydrate region of mucin type, was regioselectively synthesized from lactose and p-nitorpheny1 N-acetyl-a-galactosaminide uitilizing porcine testes beta-D-galactosidase-mediated transglycosylation^<1)>. Finally, Lacto-N-triose II glycoside, which is the common trisacccharide unit of glycosphingolipids, with two beta-(1-6)-linked isomers were synthesized through N-acetylglucosaminyl transfer by beta-N-acetylhexosaminidase from Nocardia orientalis. In this case, when an inclusion complex of p-nitrophenyl lactoside acceptor with beta-cyclodextrin was used, the regioselectivity of glycosidase-catalyzed formation of trisaccharide glycoside was substantially changed. It resulted not only in a significant increase of an overall yield of transfer products, but also in the proportion of the desired compound (GlcNAcbeta1-3Galbeta1-4Glcbeta-OC_6H_4NO_2-p). Furthermore, glycopolymers containing a series of beta-galactosyl-disaccharides were synthesized^<3)> and used as model in oligosaccharide-lectin interaction analysis. Their interaction with various lectins was investigated by double diffusion test and the inhibition of hemagglutinating activity of lectins. These water-soluble glycopolymers were shown to be an useful tool as probes of carbohy drate recognition.