Recent publications report the direct electrochemical detection of individual enzyme activity via collisions at microelectrodes, though `back of an envelope' calculations challenge the applicability of the experimental method. In the light of these studies, we present a comprehensive combined theoretical and computational analysis of the electrode response to a proximate and freely-diffusing enzyme generating an electroactive product. We further present experimental data for the enzyme catalase and critically discuss to what extent observed current transients can be unambiguously attributed to single enzyme collisions comparing detection via electrolysis of enzyme reaction products with detection through direct electron transfer reaction mediated via the enzyme.
