We, therefore, performed QM/MM calculations for representative snapshots from the MD trajectories. Since the hydrogen atom transfer (HAT) from the substrate to Cpd I is the key step in the substrate oxidation, we performed the Potential Energy Surface (PES) scan for the HAT step for each enzyme for different water models. TIP3P water model acts more efficiently, while in case of monooxygenase, OPC water model acts more efficiently. On the other hand, the SPC/E water model is the least efficient for peroxygenase and TIP3P is least efficient in case of monooxygenase among all three water models. However, it is important to note that we were unable to fully implement the OPC water model in Chemshell due to the unavailable parameter of the fourth site of OPC water model. Therefore, we believe if the complete implementation of the OPC water model in QM/MM will be done then the OPC model could get better results in the field of activation energy barrier calculation due to the implementation of a better charge model.