Trimethylphosphate and Dimethylphosphate Hydrolysis by Binuclear CdII , MnII , and ZnII -FeII Promiscuous Organophosphate-Degrading Enzyme: Reaction Mechanisms.

Organophosphate-degrading enzyme from Agrobacterium radiobacter P230 exhibits promiscuity, not only in the reactions it catalyzes, but also in the metals it uses to catalyze those reactions. Here, three different binuclear metal centers were studied: di-CdII , di-MnII and ZnII -FeII . This enzyme uses these metal centers for hydrolyzing trimethyl- and dimethyl-phosphates. Both mechanisms were studied at DFT level of theory using a cluster model approach. The ground spin state was determined for each enzyme. The outcomes confirmed that the hydrolysis of phosphotriester is faster than that of phosphodiester and in some case the phosphodiesterase reaction does not occur. The computed activation energies are in agreement with previous experimental results for phosphotriesterase enzymes.