Peroxidase biocatalysis in water-soluble ionic liquids: activity, kinetic and thermal stability

The activity and stability of commercial peroxidase was investigated in the presence of five 1-alkyl-3-methylimidazolium-based ionic liquids (ILs) with either bromide or chloride anions: [C(x)mim][X]. The peroxidase activity and stability were better for the shorter alkyl chain lengths of the ILs and peroxidase was more stable in the presence of the bromide anion, rather than chloride. The thermal inactivation profile was studied from 45 to 60 degrees C in [C(4)mim][Cl] and [C(4)mim][Br]. The activation energy was also determined. Kinetic analysis of the enzyme in the presence of the [C(4)mim][Br] or control (buffer solution) showed that the K-M value increased 5-fold and Vm decreased 13-fold in the presence of the IL. The increase in K-M indicates that this IL can reduce the binding affinity between substrate and enzyme.