Abstract
In this work, the effect of two organic polyamines (spermine and spermidine) on the fluorescence intensity and activity of bovine intestinal alkaline phosphatase (BIALP) are investigated. The interaction of BIALP with spermine and spermidine was studied in a diethanolamine buffer with 0.5 mM magnesium chloride (pH 9.8) and at two temperatures by using the fluorescence quenching method. Furthermore, the activity of enzyme was studied using UV-Vis spectrophotometry in a diethanolamine buffer with 0.5 mM magnesium chloride, at 37 °C, in the absence and presence of different concentrations of each polyamine (0-5 mM). It was demonstrated that both polyamines quenched the intrinsic fluorescence of BIALP by the static quenching process. Based on these results, the values of the binding site for both polyamines were close to each other and decreased by increasing the temperature. The calculated thermodynamic parameters (ΔH° < 0 and ΔS° < 0) also showed that the acting forces in the formation of the complex between BIALP and polyamines were hydrogen bonds and van der Waals forces with an overall favorable Gibbs free energy change (∆G° < 0). In addition, kinetic studies revealed that these polyamines enhanced the enzyme activity of BIALP in a concentration-dependent manner. This result also indicated that spermine had more of an effect on BIALP activity in the same condition. Also, molecular docking as well as thermodynamic parameters showed that hydrogen bonds and van der Waals forces played an important role in the stabilization of BIALP-polyamine complexes.