Nasim Babaknejad - Department of Biology, Faculty of Science, University of Shahrekord, P. O. Box. ۱۱۵, Shahrekord, Iran
Behzad Shareghi - Department of Biology, Faculty of Science, University of Shahrekord, P. O. Box. ۱۱۵, Shahrekord, Iran
Ali Akbar Saboury - Institute of Biochemistry and Biophysics, University of Tehran, Tehran, Iran
Sadegh Farhadian - Department of Biology, Faculty of Science, University of Shahrekord, P. O. Box. ۱۱۵, Shahrekord, Iran

The improvement of enzymes activity and stability is crucially important for their industrial applications. Nanoparticles have recently been developed to improve enzymes performance. In this study, SiO2 nanoparticles were used to stabilize bovine intestinal alkaline phosphatase (BIALP) as an enzyme system. Different spectroscopic method were performed to study enzyme-SiO2 nanoparticle interaction, including fluorescence, ultraviolet-visible absorption spectroscopy, and circular dichroism spectrum. Moreover, activity of enzyme in the presence of SiO2 nanoparticles was assayed. SiO2 nanoparticles quenched the enzyme spectra and ground state complex was formed. The results of current study showed that SiO2 nanoparticles bound to the BIALP through hydrogen bonds and van der Waals force. The Stern–Volmer quenching constant (KSV) and corresponding thermodynamic parameters of ΔH, ΔG and ΔS were calculated. In addition, the binding constant (Kb) and number of binding sites (n) were performed by fluorescence quenching method at 298 K and 308 K. Additionally, secondary and tertiary structure of BIALP in the absence and presence of SiO2 nanoparticle were analyzed by UV–vis absorption and circular dichroism spectrum. The results showed that SiO2 nanoparticle altered the secondary structure of enzyme by changing α-helix and β-sheet content of BIALP. The activity of BIALP is increased by adding various concentrations of SiO2 nanoparticle. In overall, our results suggest that SiO2 nanoparticle can bind to the BIALP and improve its activity and stability.

Alkaline phosphatase; SiO2 nanoparticle; Circular dichroism, Quenching mechanism, Fluorescence