Ca2+诱导的淀粉液化芽孢杆菌α-淀粉酶分子的生物活性和结构变化

在研究Ca²⁺对淀粉液化芽孢杆菌α-淀粉酶分子生物活性影响的基础上, 采用荧光光谱法和傅里叶变换红外光谱法研究了Ca²⁺诱导的酶分子结构变化. 结果表明, 当溶液中Ca²⁺浓度低于25.0 mmol/L时, Ca²⁺对酶分子具有激活作用; 而当Ca²⁺浓度高于25.0 mmol/L时, Ca²⁺对酶分子的生物活性具有抑制作用. 在Ca²⁺诱导的淀粉液化芽孢杆菌α-淀粉酶分子结构变化过程中, 酶分子仅发生二级结构的变化, 并不涉及其三级结构. 当Ca²⁺对酶分子具有激活作用时, 酶分子中的无规卷曲结构及β-折叠结构的含量下降, 而α-螺旋结构及β-转角结构的含量上升; 而当Ca²⁺对酶分子生物活性具有抑制作用时, 酶分子中的α-螺旋结构及β-转角结构的含量下降, 而无规卷曲结构及β-折叠结构的含量上升.

Bioactive Change and Structural Change of Bacillus Amyloliquefaciens α-Amylases Induced by Ca2+

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.