Studies on the basis of the glucosyltransfer activity of dextransucrase

阐明葡聚糖蔗糖酶反应的机理对了解多糖的生物合成具有重要意义。在本研究中，我们将重点放在了糖基转移活性的改变上，即从肠系膜白葡萄球菌中修饰葡聚糖蔗糖酶。得到以下结果：底物蔗糖和葡聚糖的结合发生在葡聚糖蔗糖酶分子中受体和供体分子的不同位点。用水溶性碳二亚胺（EDC）和磷酸二乙酯对右旋蔗糖酶进行了失活修饰。此外，用邻苯二醛和< α >-环糊精（CD-epoxd）的环氧衍生物对右旋蔗糖酶进行了亲和标记。EDC和CD-epoxd有效灭活了该酶，表明羧基对其活性很重要。通过对葡聚糖酶各自受体位点和/或给体位点修饰的广泛研究，可以提供葡聚糖酶的新功能。

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.