Steady-state kinetics of reversible heterogeneous catalytic substrate conversions in monoenzyme membrane sensors

A model is developed for a monoenzyme membrane sensor in whose coating the assayed substrate is reversibly transformed into the detected product. Equations are given for the dependence of the extent of substrate conversion on the physicochemical parameters of the enzyme reaction. It is shown that the influence of reversibility on the extent of conversion is most pronounced at high enzyme activity in the low substrate concentration range, and disappears at enzyme saturation with substrate. The sensitivity of the extent of conversion to the ratio of the Michaelis constants for the forward and reverse processes, and to the ratio of the permeability coefficients of the enzyme layer and the membrane, heightens with increasing substrate concentration and with decreasing enzyme activity.