A Time-Independent Approach to Evaluate the Kinetics of Enzyme-Substrate Reactions in Cyclic Staircase Voltammetry

In this work we refer to a simple and time-independent cyclovoltammetric approach for evaluating kinetics of chemical step of a diffusional electrocatalytic regenerative (EC’) mechanism. The methodology relies on the dependence of the maximal catalytic (or limiting) current of the cyclic steady-state voltammograms on the catalyzing agent concentration. The magnitude of the limiting cyclovoltammetric current of an EC’ mechanism depends exclusively on the rate of the chemical regenerative reaction, while it is independent on all kinetic and thermodynamic parameters related to the electrode reaction. Theoretical results of a quasireversible EC’ mechanism reveal that the limiting current of calculated cyclic voltammograms is a linear function of the square-root of the dimensionless catalytic rate parameter. Because the rate of the catalytic reaction can experimentally be modified by altering the concentration of the regenerating agent (for constant scan rate), this scenario can be explored for the determination of the catalytic rate constant. The approach described in this work is important for the enzyme-substrate catalytic reactions, since the value of the catalytic rate constant allows estimation of the Michaelis-Menten constant.