淀粉分子链重构制备低热量糊精的酶学基础研究

Low caloric dextrin is a special form of soluble dextrin rich in α-1,2、α-1,3、α-1,6 glycosidic bonds or cyclic sugar chain structure. Due to its digestive enzyme-resisting properties, low calorie dextrin has been supplemented in diets as an effective intervention measure for the control of sub-health problems such as obesity. Low caloric dextrin is mainly obtained through molecular reconstruction using starch as the raw material. Current process for its preparation is low in efficiency and high in cost, and is thus unable to meet the demands of the consumer society. The key problems in this process are the lack of specific transglycosidases and the lack of an effective measure for controlling the enzymatic reaction. In the preliminary results, we have identified more than ten different enzymes for the preparation of low calorie dextrin, including branching enzyme, α-glucosidase, and α-cyclodextrin glycosyltransferase. The proposed project will further explore the identification of new enzymes; and investigate enzyme properties, structure and function relationship, as well as the mechanism of the transglycosylation reaction. Based on these studies, the function of enzymes will be optimized through molecular modification to improve their catalytic efficiency and applicability. The mechanism for the directional and quantitative control of the complex enzyme conversion system will also be elucidated. This project provides the indispensible theoretical basis not only for the mechanistic investigation of transglycosidases but also for the more efficient preparation of low calorie dextrin, and has significance to the development of starch deep processing industry.

低热量糊精是一类富含α-1,2、α-1,3、α-1,6糖苷键或环状糖链结构的可溶性糊精的总称。低热量糊精具有抗人体消化酶特性，增加其在摄入组分中的含量是防控肥胖等亚健康问题的有效膳食干预手段。低热量糊精主要是以淀粉为原料，通过分子链重构获得。目前制备效率低、生产成本高、难以满足大众消费者的需求。导致此问题的关键是缺乏适用于低热量糊精制备体系的特异性转糖苷酶和酶反应过程调控手段。前期工作中，本课题组已获得10余种可用于低热量糊精制备的转糖苷酶，包括分支酶、α-葡萄糖苷酶以及α-环糊精葡萄糖基转移酶。项目拟进一步挖掘新酶，研究各类酶特性、结构及转苷作用机制，并在此基础上，通过分子改造优化酶功能以提高其效率和应用适应性，阐明定向有序及定量可控的复合酶转化机制。本项目将为转糖苷酶作用机制研究以及低热量糊精高效制备提供重要的理论基础，对淀粉深加工行业的发展具有积极意义。