The hydrogen-linked atom with the charge shift model was applied to treat the dangling bonds at the boundary of the QM and MM region. The QM region was treated with UB3LYP/def2-SVP level of theory at the singlet spin state and the MM region was treated with the ff19SB protein force field. This choice of basis set and QM theory aligns with established practices in enzyme and protein chemistry. The zero-point-energy (ZPE) correction was performed for all species involved in the reaction profile at the same level of theory. The energies were further refined with the higher order basis set def2-TZVP along with the Grimme dispersion (GD3) correction. All QM/MM calculations were performed using the ChemShell software of version 3.7.1 wherein TURBOMOLE was employed for the QM part and the DL_POLY module was used for the MM part.