intermediates of fluoride and bromide could suggest that oxidative decarboxylation to form Fe(IV)=O with succinate ligand might be slightly more difficult for these halides compared to the native chloride species. Nevertheless, prior experimental results demonstrate that the oxidative decarboxylation step occurs in a fluoride-bound version of the engineered enzyme SadX as proficiently as in the case where chloride or bromide are bound . Thus, we focused our reaction coordinate analysis on only the HAT and rebound steps.