Study on the stability and enzymatic property improvement of porcine pancreas lipase modified by ionic liquids using molecular simulation

Application of molecular modelling techniques to make reasonable analysis for the enzymatic properties change, reaction mechanism and further to guide the directed molecular alteration of enzymes from the molecular level is an important content of the current research in the field of enzyme engineering. While the effectiveness of ionic liquid in enhancing the stability and potency of protein pharmaceuticals has been validated for years, the underlying mechanism remains poorly understood, particularly at the molecular level. A molecular dynamics simulation was developed using a procedure that allowed a united-atom level examination of the interaction between [HOOCBMIm]⁺ and a conjugated protein represented by Porcine Pancreas lipase (PPL). Molecular dynamics (MD) simulation was performed to investigate the mechanism towards the improvement in structural stability and catalytic efficiency of the Engineered PPL by [HOOCBMIm]Cl ionic liquid. The electrostatic potential, energy change and RMSD (Root Mean Square Deviation) analysis showed the enhanced stability of engineered PPL. And the solvent accessible surface area (SASA) analysis showed the enhanced catalytic activity. The results showed that Engineered PPL's RMSD value (0.537 Å) was less than Wild-type PPL's (0.68 Å) at 335 K. This indicates that the Engineered PPL conformation becomes more stable. With binding the modifier on Wild-type PPL, we found that hydrophobicity area and SASA of Enginneerd PPL were increased. These phenomena indicate that the affinity of modifier for water generates a water layer surrounding the active center. And the electrostatic potential around the modified sites is negative before binding the modifier, that neutralization of these like charges upon modification lessens the tendency of the enzyme to unfold and also benefit for substrate into catalytic sites to enhance the catalytic activity. The results presented here provided sight into interaction between ionic liquid with the conjugated PPL at molecular level and offered a tool to analyze chemical modification to change enzymatic properties. Nevertheless, the simulation, as also attempted by this study, provides molecular insight into the chemical modification to PPL, which is essential to the design, fabrication, and application of Engineered-PPL.