The Supporting Information contains details on experimental procedures (EPR, LC-MS/MS, MD, QM:MM), RMDS curves from MD simulations, distribution histograms of C-C distances between Gly928 and Cys493, energies and vibrational corrections of all stationary points, differences in energy corrected with thermal corrections calculated at all levels of theory, values of kinetic constant rates and intrinsic kinetic isotope effect, figures of the active site for all stationary points, auxiliary product ion MS spectra of benzylsuccinate standard and details on fragmentation pattern analysis for deuterated benzylsuccinate as well as non-standard AMBER files used for MD simulation (radical Gly, radical Cys, substrates and product) and PDB files of all stationary points.