Thermal Stability and Activity Regain of Horseradish Peroxidase in Aqueous Mixtures of Imidazolium-Based Ionic Liquids

Abstract

Thermal deactivation kinetics of horseradish peroxidase (HRP) were studied from 45 to 90 degrees C in phosphate buffer and 5-25% (v,w/v) 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4] and 1-butyl-3-methylimidazolium chloride [BMIM][Cl]. HRP activity at 25 degrees C was not affected by the presence of ionic liquids up to 20% (v,w/v). Increasing the ionic liquids concentration up to 25% (v,w/v) changed the biphasic character of deactivation kinetics to an apparent single first-order step. The presence of 5-10% (v/v) [BMIM][BF4] significantly improved HRP thermal stability with lower activation energies for the deactivation second phase (83-87 kJ mol(-1)). After deactivation, enhanced activity regain of the enzyme, up to 70-80% of the initial activity, was found in 25% (v/v) [BMIM][BF4] and 10% (w/v) [BMIM][Cl] and correlated to prevalence of the deactivation first phase.

Improving the Enzyme Catalytic Efficiency Using Ionic Liquids with Kosmotropic Anions

“…20,21,23,27 There are only limited reports of biocatalysis in ILs involving a significant amount of water. [28][29][30][31][32][33][34][35] A detail description of these studies was summarized in our recent papers. 19,36 Although some factors of ILs, such as polarity 20 , hydrogen-bond basicity 37,38 and anion nucleophilicity, 39 were considered to have influences on the enzyme activity, they did not seem to be direct and universal indicators for many enzyme behaviors in ILs.…”

Direct Electrochemistry of Hemoglobin and Its Electrocatalysis Based on Hyaluronic Acid and Room Temperature Ionic Liquid

“…For electroanalytical chemistry, RTILs can be used not only as supporting electrolyte [9] but also as the modified materials. For example, 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF 4 ) considered as an excellent media for biocatalysis [10,11] has been applied to incorporating with conventional biocomposite matrixes such as carbon materials [12 -14], cellulose [15], chitosan [16], silica sol-gel [17] to investigate direct electrochemistry of redox proteins. Besides, RTILs have also mixed with graphite powder for fabrication ionic liquid carbon paste electrode (CILE) to study electrochemical behaviors of different kinds of electroactive compounds or proteins [18 -21].…”

Effects of mutations in the helix G region of horseradish peroxidase

“…The stability of HRP has a crucial bearing on its applicability and is affected by a number of variables including temperature [8,9,10], calcium content [10], glycosylation [11], pressure [12], irradiation [13] and pH [9,14], along with additional factors such as urea [15,16], guanidinium chloride [15,17] and various solvents including dimethyl sulfoxide [18] and ionic liquids [19]. Directed evolution has been used to alter rHRP thermal stability [20] but we have found no reports of HRP stability manipulation via rational, site-directed mutagenesis.…”