Application of electrochemical impedance spectroscopy for studying of enzyme kinetics

The application of electrochemical impedance spectroscopy (EIS) in theory and experiment for investigation of redox enzyme kinetics has been described. As a model system an enzyme horseradish peroxidase adsorbed on graphite electrode has been chosen. Three different mathematical models based on generalized mechanism of horseradish peroxidase catalyzed hydrogen peroxide reduction have been formulated and used for derivation of theoretical electrochemical impedances. In this way, mechanistic details related to bioelectrochemical reaction including all relevant kinetic parameters are obtained. The presented approach overcomes limitations of classical equivalent circuit approach, since it does not rely on phenomenological elements, but on particular reaction mechanism. We have shown that the EIS is more sensitive for parameter estimation and model discrimination than a steady state response.