Li Shuangshuang, Wu Wenjing, Li Jing, Zhu Shengnan, Yang Xi, Sun Lijun
College of Food Science and Engineering, Northwest A&F University, Yangling, China.
Front Nutr. 2022 Apr 13;9:817039. doi: 10.3389/fnut.2022.817039. eCollection 2022.
The courses of starch digestion with individual α-amylase (AA), amyloglucosidase (AMG), and AA/AMG bi-enzyme system were performed and analyzed by first-order-reaction equations in the absence and presence of tannic acid (TA). An antagonistic effect between AA and AMG occurred at the digestion phase of readily-digestible starch due to the higher catalytic efficiency of AMG for starchy-substrates with more complex structures. This effect caused a faster rate of glucose production with AMG than with AA/AMG bi-enzyme system at this phase both in the absence and presence of TA. TA had a higher binding affinity to AA than to AMG as accessed by several methods, such as inhibition kinetics, fluorescence quenching, isothermal titration calorimetry (ITC), and molecular docking. Besides, differential scanning calorimetry (DSC) indicated that the change in the thermal and structural stabilities of enzymes in the presence of TA was related to the enzyme residues involved in binding with TA, rather than the inhibitory effects of TA. The binding characters of TA to both enzymes resulted in more "free" AMG without TA binding in AA/AMG bi-enzyme system than that in individual AMG. This binding property caused more and faster rate of glucose production at the digestion phase of slowly digestible starch (SDS) in the bi-enzyme system.
在不存在和存在单宁酸（TA）的情况下，采用一级反应方程对单独的α-淀粉酶（AA）、淀粉葡糖苷酶（AMG）以及AA/AMG双酶系统的淀粉消化过程进行了研究和分析。由于AMG对结构更复杂的淀粉底物具有更高的催化效率，在易消化淀粉的消化阶段，AA和AMG之间出现了拮抗作用。在该阶段，无论有无TA存在，AMG产生葡萄糖的速率都比AA/AMG双酶系统更快。通过抑制动力学、荧光猝灭、等温滴定量热法（ITC）和分子对接等多种方法测定，TA与AA的结合亲和力高于与AMG的结合亲和力。此外，差示扫描量热法（DSC）表明，在有TA存在的情况下，酶的热稳定性和结构稳定性的变化与参与和TA结合的酶残基有关，而非TA的抑制作用。TA与两种酶的结合特性导致在AA/AMG双酶系统中，未与TA结合的“游离”AMG比单独的AMG更多。这种结合特性使得在双酶系统中，慢消化淀粉（SDS）消化阶段产生葡萄糖的量更多、速率更快。
