It is well established that the enzymatic local electric field (LEF) can be a descriptor of the enzymatic activity, 48-51 therefore, we probed the effect of different water models on the LEF of the enzyme. The LEF of the enzyme was calculated on the oxo moiety of heme "O" and in the direction Fe=O axis using TITAN Programs of QM/MM optimized RC, TS, and IM geometries. As can be seen from Figure , the LEF remains constant despite using the different water models i.e., OPC and SPC/E in RC, TS, and IM, however, there is a notable difference in the dipole moments of the reactive species. We found an increase in the dipole moment of 0.13 debye from RC to TS using the OPC water model for CYP450OleT, while in the case of the SPC/E water model this increment in dipole moment is 0.05 debye only.