Enhancement of Alpha-amylase's Stability and Catalytic Efficiency After Modifying Enzyme Structure Using Calcium and Ultrasound.

High thermostability and catalytic efficiency of α-amylase are required for the industrial applications. To improve catalytic parameters including Michaelis constant, maximum velocity, turnover number, enzyme half-life, and the catalytic efficiency of α-amylase, it was treated alone and/or simultaneously with Ca2+ ions (12.5 and 25 mM) and/or ultrasound (USN) (64.5 W, 25 + 40 kHz). The structural analysis of the enzyme (the enzyme's secondary structure and conformation) was carried out using Fourier transform infrared (FTIR) spectroscopy and circular dichroism (CD) techniques. Moreover, the thermal properties of the enzyme were evaluated using differential scanning calorimetry (DSC). USN + 12.5 mM Ca2+ and 25 mM Ca2+, changed the maximum velocity (+ 6.5% and + 37.4%), turnover number (+ 6.6% and + 38.2%), enzyme half-life (+ 51.6% and + 113.7%), and catalytic efficiency (+ 18.1% and -3.3%) of α-amylase. The energy barriers of thermo-inactivation and inactivation enthalpy of α-amylase exposed to USN + 25 mM Ca2+ were increased by 25% and 5.8%, respectively, without affecting entropy of inactivation, showing how enzyme's thermal stability was improved after the treatments. The increase in midpoint temperature (35%) and α-helix (14%) values as well as the decrease in the β-sheet structure (39%) of the α-amylase after applying USN + Ca2+ (25 mM) confirmed the thermal stability enhancement of α-amylase after the treatment compared to control. [ABSTRACT FROM AUTHOR]