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Theoretical Insights into the Aerobic Hydrogenase Activity of Molybdenum–Copper CO Dehydrogenase

1
Department of Earth and Environmental Sciences, University of Milano-Bicocca, Piazza della Scienza 1, 20126 Milan, Italy
2
Department of Biotechnology and Biosciences, University of Milano-Bicocca, Piazza della Scienza 2, 20126 Milan, Italy
3
Department of Theoretical Chemistry, Lund University, Chemical Centre, P.O. Box 124, SE-221 00 Lund, Sweden
*
Authors to whom correspondence should be addressed.
Inorganics 2019, 7(11), 135; https://doi.org/10.3390/inorganics7110135
Received: 14 September 2019 / Revised: 31 October 2019 / Accepted: 4 November 2019 / Published: 9 November 2019
The Mo/Cu-dependent CO dehydrogenase from O. carboxidovorans is an enzyme that is able to catalyse CO oxidation to CO 2 ; moreover, it also expresses hydrogenase activity, as it is able to oxidize H 2 . Here, we have studied the dihydrogen oxidation catalysis by this enzyme using QM/MM calculations. Our results indicate that the equatorial oxo ligand of Mo is the best suited base for catalysis. Moreover, extraction of the first proton from H 2 by means of this basic centre leads to the formation of a Mo–OH–Cu I H hydride that allows for the stabilization of the copper hydride, otherwise known to be very unstable. In light of our results, two mechanisms for the hydrogenase activity of the enzyme are proposed. The first reactive channel depends on protonation of the sulphur atom of a Cu-bound cysteine residues, which appears to favour the binding and activation of the substrate. The second reactive channel involves a frustrated Lewis pair, formed by the equatorial oxo group bound to Mo and by the copper centre. In this case, no binding of the hydrogen molecule to the Cu center is observed but once H 2 enters into the active site, it can be split following a low-energy path. View Full-Text
Keywords: CO dehydrogenase; dihydrogen; hydrogenase; quantum/classical modeling; density functional theory CO dehydrogenase; dihydrogen; hydrogenase; quantum/classical modeling; density functional theory
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Rovaletti, A.; Bruschi, M.; Moro, G.; Cosentino, U.; Greco, C.; Ryde, U. Theoretical Insights into the Aerobic Hydrogenase Activity of Molybdenum–Copper CO Dehydrogenase. Inorganics 2019, 7, 135.

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