关键词: 地衣芽孢杆菌, 热稳定性, &alpha, -淀粉酶, 构象

Abstract: The influence of heat on the conformation and stability of α-amylase α-Ⅲ fraction from Bacillus Licheniformis A.4041 was studied by means of the fluorescence and CDspectra. Heated at 80 ℃ for 15 min, the enzyme hardly lost its activity. At the same time, a considerable change of its fluorescence and CDspectra was observed. It was shown that, comparing with the whole conformation of the enzyme molecule, the active site has a relative stability. Heated at 90 ℃ for 15 min, the conformational and active changes resulted by Ca ²⁺ and starch were different. The Ca²⁺ mainly affects the whole enzyme molecular conformations, whereas the substrate is important to sustain the activity. It indicates that the structure of enzymatic active site plays an important role to the thermostability of the α-Ⅲ.

Key words: Bacillus licheniformis, Thermostability, α-Amylase, Conformation