Kinetic and amperometric study of the MtPerII peroxidase isolated from the ascomycete fungus Myceliophthora thermophila

Abstract

The enzyme MtPerII is a new peroxidase which has been isolated only recently from fungus Myceliophthora thermophila and has significant thermostability and stability at high H₂O₂ concentrations. In the present work, an electrochemical kinetic study, based on cyclic voltammetry, is performed for the first time for the catalytic decomposition of H₂O₂ by MtPerII, at 18°C. Leuco methylene blue (LMB) is used as a mediator and the catalytic and Michaelis constants are determined, assuming a Michaelis-Menten mechanism. Experimental evidence suggest the absence of inhibition by H₂O₂, for concentrations up to 16mM, and increasing catalytic activity for temperatures up to 50°C. Moreover, a modified electrode is constructed, by attempting the entrapment of MtPerII on a dodecanothiol self-assembled monolayer on gold. The modified electrode is studied chronoamperometrically in solutions containing methylene blue mediator and different concentrations of H₂O₂. It is shown that adsorbed MtPerII retains its activity and the modified electrode exhibits a considerably high linear region for the detection of H₂O₂. The experimental findings indicate that MtPerII is a new candidate for analytical and industrial applications.

Keywords: Amperometric response; Biocatalysis; Cyclic voltammetry; Hydrogen peroxide; MtPerII peroxidase.