CO Oxidation Mechanism of Silver-Substituted Mo/Cu CO-Dehydrogenase - Analogies and Differences to the Native Enzyme.

Autor: Rovaletti A; Department of Earth and Environmental Sciences, Milano-Bicocca University, Piazza della Scienza 1, Milano, 20126, Italy., Moro G; Department of Biotechnology and Biosciences, Milano-Bicocca University, Piazza della Scienza 2, Milano, 20126, Italy., Cosentino U; Department of Earth and Environmental Sciences, Milano-Bicocca University, Piazza della Scienza 1, Milano, 20126, Italy., Ryde U; Department of Theoretical Chemistry, Lund University, Chemical Centre, P.O. Box 124, SE-221 00, Lund, Sweden., Greco C; Department of Earth and Environmental Sciences, Milano-Bicocca University, Piazza della Scienza 1, Milano, 20126, Italy.
Jazyk: angličtina
Zdroj: Chemphyschem : a European journal of chemical physics and physical chemistry [Chemphyschem] 2024 Jul 02; Vol. 25 (13), pp. e202400293. Date of Electronic Publication: 2024 May 25.
DOI: 10.1002/cphc.202400293
Abstrakt: The aerobic oxidation of carbon monoxide to carbon dioxide is catalysed by the Mo/Cu-containing CO-dehydrogenase enzyme in the soil bacterium Oligotropha carboxidovorans, enabling the organism to grow on the small gas molecule as carbon and energy source. It was shown experimentally that silver can be substituted for copper in the active site of Mo/Cu CODH to yield a functional enzyme. In this study, we employed QM/MM calculations to investigate whether the reaction mechanism of the silver-substituted enzyme is similar to that of the native enzyme. Our results suggest that the Ag-substituted enzyme can oxidize CO and release CO 2 following the same reaction steps as the native enzyme, with a computed rate-limiting step of 10.4 kcal/mol, consistent with experimental findings. Surprisingly, lower activation energies for C-O bond formation have been found in the presence of silver. Furthermore, comparison of rate constants for reduction of copper- and silver-containing enzymes suggests a discrepancy in the transition state stabilization upon silver substitution. We also evaluated the effects that differences in the water-active site interaction may exert on the overall energy profile of catalysis. Finally, the formation of a thiocarbonate intermediate along the catalytic pathway was found to be energetically unfavorable for the Ag-substituted enzyme. This finding aligns with the hypothesis proposed for the wild-type form, suggesting that the creation of such species may not be necessary for the enzymatic catalysis of CO oxidation.
(© 2024 Wiley-VCH GmbH.)
Databáze: MEDLINE
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