Study on the interaction between calcium ions and alkaline protease of bacillus

The interaction between Ca2+ and alkaline protease has been studied. Enzyme activity measurements demonstrated that Ca2+ with a suitable concentration could increase the activity of alkaline protease. Particle size and zeta potential measurements showed that Ca2+ bound to alkaline protease by electrostatic interaction. The combination of Ca2+ and alkaline protease promoted the structure of alkaline protease to become more stable, which was favorable for the increase of enzyme activity. Fluorescence spectra showed that alkaline protease had two Ca2+ binding sites and potent binding force to Ca2+. Thermodynamic parameters ΔH, ΔS and ΔG obtained by fluorescence spectra confirmed that the interaction between Ca2+ and alkaline protease was also electrostatic interaction and the binding process could proceed spontaneously. The results of molecular docking were also consistent with the conclusions obtained from the zeta potential and fluorescence spectrum measurements. In addition, the washing performance test showed that the detergent added with Ca2+ and alkaline protease had the best washing performance on protein-contaminated swatches JB02 and blood swatches.