“…The exploration of enzyme-catalyzed reactions and their remarkable rate acceleration has been the subject of extensive computational research. − Among the methods employed, the hybrid quantum mechanical and molecular mechanical (QM/MM) approach stands out as the most widely adopted method. − In contrast to MM potentials, QM methods offer a more accurate description of chemical events involving the formation and cleavage of chemical bonds, as well as oxidation and reduction processes at the active site. However, representing the entire enzyme system at a QM level of theory is computationally prohibitive, especially when multiple protein and solvent configurations must be sampled to estimate free energies and other thermodynamic properties. , In the QM/MM method, regions of the system with chemical relevance are treated with electronic structure methods, such as ab initio (ai) or semiempirical (se) QM and density functional theories (DFTs), while the remaining regions are described with simplified MM force fields. − ,− Because of such effectiveness, this method is considered the most practical method for simulating enzymatic reactions and is often combined with various free energy simulation methods, including umbrella sampling, metadynamics, , and string methods, , to facilitate the investigation of enzyme reaction mechanisms. ,,,− …”