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 CO2 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.

中文翻译：

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银取代的Mo/Cu CO脱氢酶的CO氧化机制。与天然酶的相似性和差异

一氧化碳有氧氧化成二氧化碳是由土壤细菌寡养菌中的含钼/铜的CO脱氢酶催化的，使该生物体能够以小气体分子作为碳和能源生长。实验表明，银可以取代Mo/Cu CODH活性位点中的铜，产生功能性酶。在本研究中，我们采用 QM/MM 计算来研究银取代酶的反应机制是否与天然酶相似。我们的结果表明，Ag 取代酶可以按照与天然酶相同的反应步骤氧化 CO 并释放 CO2，计算出的限速步骤为 10.4 kcal/mol，与实验结果一致。令人惊讶的是，在银存在的情况下，发现 C-O 键形成的活化能较低。此外，含铜和含银酶的还原速率常数的比较表明，银取代时过渡态稳定性存在差异。我们还评估了水活性位点相互作用的差异可能对催化的整体能量分布产生的影响。最后，发现沿着催化途径形成硫代碳酸盐中间体对于银取代酶来说在能量上是不利的。