ИСТИНА

Ionic liquids (ILs) find wide use in biocatalysis as solvent, or co-solvents in aqueous and biphasic systems, in place of the common organic solvents [1]. One of the advantages of their use is the possibility of choosing an appropriate cation аnd/or anion to modulate chemico-physical properties (polarity, ion chaotropicity and kosmotropicity, viscosity, hydrophobicity, H-bond basicity, Hofmeister effects) allowing to tailor the most suitable solvent for a given biocatalytic reaction [2,3]. Many studies refer to the Hofmeister series to estimate the possible effect of IL’s ions on protein stability. Generally, experimental works confirm a greater stabilization (or destabilization) by ions in accordance with the Hofmeister series. However, for different enzymes the order can be reversed, depending on the type of protein and the reaction conditions. Thus, every enzymatic system represents a special case [4]. Specifically, in this work we investigated the activity and stability of the NAD+-dependent formate dehydrogenase (EC 1.2.1.2, FDH) from bacterium Pseudomonas sp. 101, in the presence of different percentages of ILs based on imidazole cation ([Mmim][DMP], [Bmim][Br], [Bmim][MeSO4], [Bmim][BF4] and [Bmim][Tf2N]); the anion effect at different conditions of temperature and ionic strength was evaluated. FDH is a very important enzyme in biocatalysis, mainly used in coupled systems for the regeneration of the cofactor. Therefore, it could be interesting, for many biocatalytic applications, to improve the stabilization of this type of enzyme in the presence of ILs used as co-solvents. Moreover, the goal is to assess whether the ILs, taken into consideration, can act as enzyme stabilizers, as indicated by some data in literature. Our study, still in progress, indicates that although at high concentrations of ILs (> 20% v/v) there is a drastic loss of catalytic activity compared to the control (without IL), for low values of ILs (≤ 20 v/v), there is a moderate, but significant, increase in activity up to 25 % or 15 % with [Bmim][BF4] (1% v/v) or [Bmim][MeSO4] (20% v/v), respectively. This work was supported by joint grant between Italian side and grant number and Russian Foundation for Basic Research 15-54-78035 References: [1] Fred van Rantwijk, Roger A. Sheldon, Biocatalysis in Ionic Liquids, Chem. Rev. (Washington D. C.), 2007, 107, 2757–2785 [2] Zhao, H, Protein stabilization and enzyme activation in ionic liquids: specific ion effects. J. Chem. Technol. Biotechnol., 2016, 91, 25–50 [3] M. Naushad, Z.A. Alothman, A.B. Khan, M. Ali, Effect of ionic liquid on activity, stability, and structure of enzymes: a review, Int. J. Biol. Macromol. (2012) 51 555–560. [4] Awanish Kumar and P. Venkatesu, Review: Does the stability of proteins in ionic liquids obeys the Hofmeister series? International Journal of Biological Macromolecules, 2014, 63, 244-253