“…Notably, the oxo rotation is a continuous process in the decarboxylation starting from the Fe(III)-OO The change in the free energy of the reaction ∆Gr from IM2 to IM4 is associated with a value of -41.1 kcal/mol, indicating the overall decarboxylation reaction process is significantly exergonic ( Figure 2H), which is consistent with previous studies on non-heme iron αKG dependent enzymes 6,40 . The IM4 exhibits a 5C trigonal bipyramid geometry, consistent with the results The dominant spin states of iron in non-heme enzymes remains a long controversy 40,43,44, 64-66 , although quintet state has recently been suggested to be the ground state for the resting state and the Fe (IV)=O intermediate in other non-heme enzymes 45,46,55,56,57 , Since the ground state may change along the sequential reaction steps, here we calculated the different spin states (namely, triplet, quintet and septet spin states) of all the species involved in the decarboxylation process using QM/MM optimization. It is shown that the quintet state is consistently the ground state for all the species in the reaction process (Table S2).…”