Thermodynamic Properties of Hydrogen Peroxide Binding to Bovine Liver Catalase

Abstract

Catalase [CAT: EC 1.11.16] was purified from bovine liver using cellulose affinity chromatography and some enzyme characteristics were investigated. The interaction of H2O2 with catalase was investigated by fluorescence spectroscopy, and the change in intrinsic fluorescence intensity at 435 nm was used to estimate the association constant of the interaction. The binding process resulted in a change in the intrinsic fluorescence. The emission spectra were analyzed according to a model described by Chipman et al., to obtain the association constant (ka ) values in the temperature range of 25-50 ?C. The results showed that the association constants were temperature dependent. The value of Ka at 25°C was 2.4 × 105 M –1. Moreover, the thermodynamic parameters for the interaction H2O2/BLC were obtained from Van't Hoff plot. The results indicated that the interaction was enthalpically driven accompanied by negative entropic contribution in the studied temperature range. The association constant values were determined from Van't Hoff plots. Key words: Bovine liver catalase, fluorescence emission, association constants, thermodynamic parameters, Chipman model.