Extremely high stability of African oil palm tree peroxidase

A detailed kinetic study on thermal inactivation of African oil palm tree peroxidase (AOPTP) at different pHs has been carried out. The enzyme does not undergo inactivation over a broad range from pH 2 to 12 at ambient temperature. Complete inactivation of AOPTP is observed only at 70 degrees C and extremal pHs like <3.0 and >12.0, whereas under neutral conditions, its activity shows no changes. The study of AOPTP inactivation kinetics in the presence of dithiothreitol (DTT) and ethylenediaminetetraacetic acid (EDTA) showed that calcium ions, disulfide bonds and the interaction between apo-AOPTP and heme are important structural elements responsible for the enzyme stability. The guanidium hydrochloride (GdHCl)-induced inactivation of AOPTP indicated that the hydrogen-bonding network plays also a significant role in stabilizing the active structure of the enzyme. AOPTP is stable toward hydrogen peroxide treatment, especially under neutral conditions. The comparison of AOPTP stability to that of other peroxidases shows that AOPTP is the most stable peroxidase reported so far.