Let us consider here that the system at hand involves a simple canonical Michaelis-Menten (MM) enzymatic mechanism (Scheme 1) converting a non-electroactive substrate, present at concentration in the analyzed bulk solution, into an electroactive product 𝑃 detected at a micro-or nanoelectrode surface on which a thin enzyme coating is deposited (Figure ) . Note that by "thin" we mean that the thickness of the enzyme layer is extremely small relatively to the dimension of the electrode, therefore also vs. that of the diffusion layers which spontaneously establish in a few seconds in the enzyme-free solution surrounding the electrode . Therefore, one may rightly consider that most of the current flow stems from the electrolysis of the product generated in the enzyme layer without significant losses due to diffusion towards the bulk solution . On the other hand, owing to the flux conservation of the substrate one has at any time: