Inactivation kinetics of horseradish peroxidase (HRP) by hydrogen peroxide

In recent years, the peroxidase enzymes have generated wide interest in several industrial processes, such as wastewater treatments, food processing, pharmaceuticals, and the production of fine chemicals. However, the low stability of the peroxidases in the presence of hydrogen peroxide (H(2)O(2)) has limited its commercial use. In the present work, the effect of H(2)O(2) on the inactivation of horseradish peroxidase (HRP) was evaluated. Three states of HRP (E(0), E(2), and E(3)) were identified. While in the absence of H(2)O(2), the resting state E(0) was observed, in the presence of low and high concentrations of H(2)O(2), E(2,) and E(3) were found, respectively. The results showed that HRP catalyzed the H(2)O(2) decomposition, forming the species E(x), which was catalytically inactive. Results suggest that this loss of enzymatic activity is an intrinsic characteristic of the studied HRP. A model from a modified version of the Dunford mechanism of peroxidases was developed, which was validated against experimental data and findings reported by the literature.