As shown in the previous section, syringol in F169A mutant has two possible binding conformations-A and B. We, therefore, performed two separate QM/MM calculations to decipher how these alternate conformations contribute towards the catalysis. Figure shows the reaction profile for conformations A and B in red and black colours respectively. In both conformations, the aryl-O-demethylation occurs via HAA similar to Figure and are consistent with the previous DFT studies on the syringol oxidation. The TS barriers for the HAA process for both conformations are 18.3 and 16.3 kcal/mol, respectively, and the TS barrier of the HAA process in conformation B is lower in energy by 2.0 kcal/mol. Note that conformation A belongs to the conformation similar to WT, and therefore we suggest that the F169A mutation causes enhanced flexibility, and hence substrate adopts an alternative conformation (i.e., B) which is more reactive. The experimental findings suggest that the F169A performs two rounds of O-demethylation on the methoxy groups of syringol to yield pyrogallol. Therefore, were performed QM/MM calculation for the O-demethylation of 3MC using a similar protocol as above. We found that the TS barrier for HAA for the mutant is 17.6 kcal/mol which is almost similar to the TS barrier for HAA reaction in syringol as substrate and follows a similar barrierless rebound step for the exothermic IM2 production (Figure ).