The effect of spermine on the structure, thermal stability and activity of bovine pancreatic trypsin

Abstract

This work studied the interaction between spermine and trypsin at pH 8.0. The thermal stability of trypsin was investigated in the presence of spermine over a temperature range (from 293 K to 353 K). Additionally, the conformational change of trypsin induced by spermine was analyzed by UV-vis absorption and fluorescence spectra. The effect of spermine on trypsin activity was studied at 37 °C and pH 8.0, using Tris–HCl as a buffer. The fluorescence spectroscopy results indicated that the binding of spermine to trypsin was a spontaneous binding process. The fluorescence of trypsin was quenched by spermine through the static quenching mechanism. By increasing the concentration of spermine, the thermal stability of trypsin was increased. The quantitative analysis of CD spectra revealed some information regarding the changes in the content of the α-helix and the β-sheet of the trypsin upon binding to spermine. It was also found that by increasing the concentration of spermine, the activity of trypsin was increased. Molecular docking results also revealed the presence of one binding site with a negative value for the Gibbs free energy of the binding of spermine to trypsin. Further, the docking and fluorescence spectroscopy study revealed that van der Waals interactions and hydrogen bonds played a major role in stabilizing the complex. As a result, spermine could be considered as an activator and stabilizer for trypsin.