Evaluation of the enzymatic activity of catalase in aqueous mediums of basic amino acids based deep eutectic solvents

We analyzed catalase's function, structure, and thermal stability in two basic amino acid-based deep eutectic solvents due to the importance of studying the enzymatic behavior in suitable non-aqueous media. We used various UV-visible spectroscopic methods, fluorescence, and circular dichroism (CD). Combining arginine with glycerol and lysine with glycerol was applied to form two distinct amino acid-based deep eutectic solvents. Kinetic studies showed that forming an intricate hydrogen bond network between glycerol and amino acid components in arginine or lysine-based aqueous deep eutectic solvents of 45% and 40%, respectively, keeps the catalase activity near 50%. Our outcomes demonstrated that the intrinsic fluorescence of the catalase is quenched by increasing the concentration of these solvents via a static mechanism. Also, CD results have further represented remarkable changes in arginine-glycerol and lysine-glycerol solvents with a diminished α-helical content and an increase in β-pleated sheets content. Studies of the thermal stability of catalase in the presence of these solvents showed that with increasing concentration of these solvents, the thermal stability of enzyme (T m and ΔG° values) decreases. Finally, the above data suggested that arginine and lysine with chaotropic factors of guanidine and ammonium in their functional group, respectively, act as influential factors in the activity and structural stability of the enzyme.