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 quantumchemical 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. [ABSTRACT FROM AUTHOR]