Ashida H, Yamamoto K, Kumagai H
Laboratory of Molecular Biology of Bioresponse, Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Japan.
Carbohydr Res. 2001 Feb 28;330(4):487-93. doi: 10.1016/s0008-6215(01)00008-8.
Thomsen-Friedenreich antigen (T antigen) disaccharide, beta-D-galactose-(1-->3)-alpha-N-acetyl-D-galactosamine (beta-D-Gal-(1-->3)-alpha-D-GalNAc), containing glycolipid mimicry was synthesized using the transglycosylation activity of endo-alpha-N-acetylgalactosaminidase from Bacillus sp. This enzyme could transfer the disaccharide from a p-nitrophenyl substrate to water-soluble 1-alkanols and other alcohols at a transfer ratio of 70% or more. Although the transfer ratios were lower for water-insoluble than water-soluble alcohols, they were shown to increase by adding sodium cholate to the reaction mixtures. The enzyme also transferred the disaccharide directly from asialofetuin to 1-alkanols. The anomeric bond between the disaccharide and 1-alkanols of the transglycosylation product is in the alpha configuration as determined by sequential digestion of jack bean beta-galactosidase and Acremonium alpha-N-acetylgalactosaminidase. Since the transglycosylation product, beta-D-Gal-(1-->3)-alpha-D-GalNAc-(1-->O)-hexyl, efficiently inhibits the binding of anti-T antigen monoclonal antibody to asialofetuin, it has potential as an agent for blocking T antigen-mediated cancer metastasis.
利用芽孢杆菌属的内切α-N-乙酰半乳糖胺酶的转糖基化活性，合成了含有糖脂模拟物的汤姆森-弗里德赖希抗原（T抗原）二糖，即β-D-半乳糖-（1→3）-α-N-乙酰-D-半乳糖胺（β-D-Gal-（1→3）-α-D-GalNAc）。该酶能够将二糖从对硝基苯基底物转移至水溶性1-链烷醇和其他醇类，转移率达70%或更高。尽管对于水不溶性醇类的转移率低于水溶性醇类，但通过向反应混合物中添加胆酸钠，转移率会升高。该酶还能将二糖直接从去唾液酸胎球蛋白转移至1-链烷醇。通过刀豆β-半乳糖苷酶和顶头孢霉α-N-乙酰半乳糖胺酶的顺序消化确定，转糖基化产物中二糖与1-链烷醇之间的异头键为α构型。由于转糖基化产物β-D-Gal-（1→3）-α-D-GalNAc-（1→O）-己基能有效抑制抗T抗原单克隆抗体与去唾液酸胎球蛋白的结合，因此它有潜力作为阻断T抗原介导的癌症转移的药物。
