title: 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.
authors.affiliation: Departamento de Química, Universidade de Aveiro, Campus Universitário de Santiago, 3810-193, Aveiro, Portugal.
authors.forename: Maria Fátima
authors.initials: MF
authors.lastname: Machado
authors.forename: Jorge Manuel
authors.initials: JM
authors.lastname: Saraiva
mesh_terms: D045424:Complex Mixtures / Q000032:analysis / Q000737:chemistry*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000737:chemistry; D006735:Horseradish Peroxidase / Q000032:analysis* / Q000737:chemistry*; D007093:Imidazoles / Q000032:analysis / Q000737:chemistry*; D007477:Ions; D007700:Kinetics; D012996:Solutions; D013696:Temperature; D014867:Water / Q000737:chemistry*
chemical_list: D045424:Complex Mixtures; D004791:Enzyme Inhibitors; D007093:Imidazoles; D007477:Ions; D012996:Solutions; D014867:Water; D006735:Horseradish Peroxidase