A theoretical study on the reactivity of the Mo/Cu-containing carbon monoxide dehydrogenase with dihydrogen.

The Mo/Cu-dependent CO dehydrogenase from Oligotropha carboxidovorans is an enzyme that is able to catalyze CO oxidation to CO2; moreover, it can also oxidize H2, thus eliciting a characteristic EPR signal. Interestingly, the Ag-substituted enzyme form proved unable to catalyze H2 oxidation. In the present contribution, we characterized the reactivity of the enzyme with H2 by quantum-chemical calculations. It was found that dihydrogen binding to the wild-type enzyme requires significant structural rearrangements of the active site Theoretical EPR spectra for plausible H2-bound models of the partially reduced, paramagnetic active site are also presented and compared with the experimental counterpart. Finally, density functional theory modeling shows that Ag substitution impairs H2 binding at the active site.