Characterization of osmolyte-enzyme interactions using different spectroscopy and molecular dynamic techniques: Binding of sucrose to proteinase K.

Osmolytes such as sucrose can interact with the proteins. The aim of the present investigation was to characterize how sucrose could affect the structure, thermal stability and the kinetic of proteinase K. UV-vis spectroscopy, fluorescence spectroscopy, circular dichroism, molecular docking, molecular dynamic simulation studies were used to this end. The UV-vis results are represented the intensity enhancement 270 nm due to alteration in the local environment of Tyr and Trp amino acid residues illustrated the tertiary structure changes of proteinase K. The intrinsic fluorescence intensity was decreased regularly with increase the ligand concentration. The secondary structure alterations were revealed an increase in the α-helix content of enzyme. The activity of enzyme was increased in the presence of sucrose. Thus, sucrose is an activator for proteinase K. Molecular docking results show a negative value for the Gibbs free energy of the binding confirming the spontaneous proteinase K-sucrose complexation and in agreement with fluorescence results. On the other hand, the thermal stability of proteinase K was investigated in the presence of sucrose. The obtained results show that sucrose led to increment the stability of enzyme in a concentration dependent manner. These results are confirmed by the molecular dynamic simulation technique.