The autocatalysis with P3 was performed under the same conditions than P2. The resulting kinetics curves (see Figure ) characterizing the NADH consumption as a function of time, show, similarly to P2, well-defined S-shaped kinetics traces with longer lags as the triggering H2O2 concentration is lower. However, a main difference with P2 is the much slower kinetics, requiring for the lowest concentrations more than 5 hrs to reach t1/2, while it takes less than 10 min with P2. Such a huge difference can be understood from the slower deprotection rate of P3 with respect to P2, as well as from the need of two equivalents of H2O2 to fully deprotect each P3 molecule. The analytical performances indicate a dynamic concentration range over more than two decades (i.e., from 0.1 to 20 µM H2O2) and a LOD of 0.2 µM H2O2. These analytical performances are not as good as expected, leading to a LOD similar to that of P2, which is surprising if we consider the much higher chemical stability of P3. In order to improve the reaction rate and at the same time the analytical performances, we reproduced the autocatalysis at a slightly more basic pH (pH 9.5). The resulting autocatalytic responses in Figure show a clear kinetic gain, reducing the t1/2 values to a time window < 40 min. Compared to the results obtained at pH 8.5, this corresponds to an analysis time improvement by a factor 10. Moreover, the extracted H2O2 calibration curve (Figure ) demonstrates a better LOD of 20 nM, which is again a 10-fold improvement compared to pH 8.5 (Figure ). Clearly, the pH has a strong impact on the analytical performances of the system, since by changing the pH of one unit, both LOD and analysis time are improved 10-fold. All these results led us to investigate what could lead to such a drastic pH effect, but also how to interpret the large rate difference between P3 and P2. To this end, we examined the possibility to simulate the autocatalytic kinetic traces on the basis of a reasonable set of reactions for describing the cross coupling between the H2O2-mediated catalytic deprotection of P3 (Loop 1) and the enzyme-assisted redox cycling (Loop 2) (see thereafter).