STUDIES ON THE THERMOSTABILITY AND CONFORMATION OF THERMOSTABLE ALPHA-AMYLASE FROM BACILLUS-LICHENIFORMIS-A-4041

The influence of heat on the conformation and stability of alpha-amyla se alpha-III fraction from Bacillus Licheniformis A, 4041 was studied by means of the fluorescence and CD spectra, Heated at 80 degrees C fo r 15 min, the enzyme hardly lost its activity, At the same time, a con siderable change of its fluorescence and CD spectra was observed. It w as shown that, comparing with the whole conformation of the enzyme mol ecule, the active site has a relative stability. Heated at 90 degrees C far 15 min, the conformational and active changes resulted by Ca2+ a nd starch were different. The Ca2+ mainly affects the:whole enzyme mol ecular conformations, whereas the substrate is important to sustain th e activity, It indicates that the structure of enzymatic active site p lays an important role to the thermostability of the alpha-III.