Activation/Inactivation Role of Ionic Liquids on Formate Dehydrogenase from Pseudomonas sp 101 and Its Mutated Thermostable Form

Ionic liquids (ILs) are used in numerous research areas including biocatalysis. The effect of ILs/water mixture on the activity of wild type and a more thermally and chemically stable mutant (SM4) of a specific formate dehydrogenases (PseFDH, EC1.2.1.2) were studied experimentally and by molecular dynamics (MD) simulations. The ILs investigated were [Mmim][Me2PO4], [Bmim][Br], [Bmim][CH3SO3], [Bmim][BF4], [Bmim][AcO], and it was found that low concentrations (optimally 2.5%) of some ILs increased (up to 42%) the activity of the SM4 FDH but not of the WT FDH. Using intrinsic fluorescence to calculate Stern-Volmer constants and thermodynamic parameters, we have studied protein conformational changes caused by ILs for both enzymes. Kinetic analyses allowed us to shed light on the mechanism of activation by 2.5% [Bmim][BF4] on the mutant enzyme. MD simulation provided evidences of a molecular basis of different enzyme activities in ILs that well correlated with the experimental data.