The barrier of <4 kcal/mol and free energy difference ~2 kcal/mol obtained with DFTB3/MM are small enough to assume that multiple acts of such interconversion may happen within one reaction or covalent inhibition cycle. To get additional support for these values, we modeled the same process in dynamics with a higher-level PBE method. The resulting free energy profile is qualitatively similar to the DFTB3-produced one. The values for the barrier and free energy difference -1.65 and 1.39 kcal/mol respectively -are smaller, which is to be expected given the nature of simplifications used in DFTB. Our PBE results enforce the idea of constant dynamical interconversion. We note that our PBE results are in good quantitative agreement with the study performed on hBChE with the protonated His438, but intact Ser198. It may be concluded that DEP-BChE can not be thought of as having only one particular protonation state of its active site. Instead, it is a rapidly interchanging ensemble of two.