Zhang Huang, Zhang Fengjiao, Wu Fengfeng, Guo Lichun, Xu Xueming
College of Food and Biological Engineering, Henan University of Animal Husbandry and Economy, No. 6, Longzihu North Road, Zhengzhou 450046, China.
The State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Synergetic Innovation Center of Food Safety and Nutrition, Jiangnan University, Wuxi 214122, China.
Foods. 2025 May 9;14(10):1679. doi: 10.3390/foods14101679.
Endogenous α-amylase activity is crucial for determining the end-use value of glutinous rice flour (GRF), and controlling it is a key goal in the milling process. Although the structure and properties of starch and protein in GRF have been extensively studied, there is little information on endogenous α-amylase in GRF. In this study, endogenous α-amylase isolated from GRF was purified and characterized. It was found to have a molecular weight of about 32 kDa, with the highest specific activity at 60 °C and a pH of 6.0. The enzyme is stable below 50 °C and in the pH range of 4.0-7.0. Its activity is Ca⁺-independent but inhibited by Cu⁺, Zn⁺, Mg⁺, Mn⁺, and Ba⁺. Its activity is also reduced by β-mercaptoethanol. The enzyme hydrolyzes amylopectin most efficiently. Circular dichroism spectroscopy showed that the enzyme contains 7.9% α-helix, 35.4% β-folding, 21.1% β-turning, and 35.9% random coils, with a T value of 63.68 °C. These results suggest that temperature control may be the best strategy for reducing amylase activity in dry-milled GRF, providing a new approach for the development of GRF dry-milling techniques.
内源α-淀粉酶活性对于确定糯米粉（GRF）的最终使用价值至关重要，控制该活性是碾磨过程中的关键目标。尽管GRF中淀粉和蛋白质的结构与特性已得到广泛研究，但关于GRF中内源α-淀粉酶的信息却很少。在本研究中，从GRF中分离出的内源α-淀粉酶被纯化并进行了表征。结果发现其分子量约为32 kDa，在60°C和pH值为6.0时具有最高比活性。该酶在50°C以下以及pH值4.0 - 7.0范围内稳定。其活性不依赖Ca⁺，但受到Cu⁺、Zn⁺、Mg⁺、Mn⁺和Ba⁺的抑制。β-巯基乙醇也会降低其活性。该酶对支链淀粉的水解效率最高。圆二色光谱显示该酶含有7.9%的α-螺旋、35.4%的β-折叠、21.1%的β-转角和35.9%的无规卷曲，T值为63.68°C。这些结果表明，温度控制可能是降低干法碾磨GRF中淀粉酶活性的最佳策略，为GRF干法碾磨技术的发展提供了一种新方法。
