Studies on the basis of the glucosyltransfer activity of dextransucrase

由于对多糖生物合成的了解，葡聚糖酶反应机理的阐明具有重要意义。本研究针对肠系膜明串珠菌葡萄糖转移活性的变化，对其葡萄糖转移酶的修饰进行了研究。得到以下结果：底物蔗糖和葡聚糖结合在葡聚糖酶分子中受体和供体分子的不同位置。用水溶性碳二亚胺(EDC)和碳酸二乙酯对葡聚糖酶进行修饰，使其失活。此外，还用邻苯二甲醛和环糊精的环氧化物(CD-Epoxd)亲和标记了葡糖酶。EDC和CD-Ecoxd对该酶的有效失活表明，羧基对该酶的活性是重要的。通过对葡萄糖转移酶各自受体和/或供体位点修饰的广泛研究，可以提供该酶的一种新的功能。

Mechanism of the dextransucrase reaction is important to clarify because of the understanding of the polysaccharide biosynthesis. In this research, we focused our attention on the modification of dextransucrase from Leuconostoc mesenteroides reffering to the change in the activity of glucosyltransfer. The following results were obtained; binding of the substrates, sucrose and dextran, occurred at the separate sites in the dextransucrase molecule for the acceptor and donor molecules. Dextransucrase was inactivated by the modification with water-soluble carbodiimide (EDC) and diethylphro-carbonate. Moreover, an affinity labeling of dextransucrase was conducted by orthophthalaldehyde and epoxide derivative of <alpha>-cyclodextrin (CD-epoxd). Effective inactivation of this enzyme with EDC and CD-epoxd suggested that a carboxyl group was important for the activity. A new function of dextransucrase could be provided by the extensive survey on the modification of respective acceptor- and/or donor-sites of the enzyme.