Abstract:

Based on the effect of bivalent calcium ions(Ca²⁺) on the biological activity of Bacillus amyloliquefaciens α-amylases, the structural change of Bacillus amyloliquefaciens α-amylases induced by Ca²⁺ was studied via fluorescence spectroscopy and Fourier-transformation infrared spectroscopy. The results showed that when the concentration of Ca²⁺ in solution was below 25 mmol/L, the enzyme molecules could be activated by Ca\+2+ in solution, when the concentration of Ca²⁺ was over 25 mmol/L, the biological activity of enzyme molecules could be inhibited by Ca²⁺. In the structural change of Bacillus amyloliquefaciens α-amylases induced by Ca²⁺, only their secondary structures rather than their tertiary structures were involved; and when Ca²⁺ showed an activation effect to the bioactivity of the enzyme molecules, the contents of disorder structures and β-sheet structures in the enzyme molecules decreased, and the α-helix ones and the β-turn ones increased. Whereas when Ca²⁺ showed an inhibition effect to the bioactivity of the enzyme molecules, the α-helix structures and β-turn structures in the enzyme molecules decreased, and disorder ones and the β-sheet ones in the enzyme molecules increased.

Key words: Bacillus amyloliquefaciens α-amylase, Ca²⁺, Biological activity, Secondary structure