Antiferromagnetically coupled [Fe8S9] cluster catalyzed acetylene reduction in a nitrogenase-like enzyme DCCPCh: Insights from QM/MM calculations

Autor: Jing-Xuan Zhang, Rong-Zhen Liao, Per E. M. Siegbahn, Zhenyang Lin
Rok vydání: 2021
Předmět:
Zdroj: Journal of Catalysis. 398:67-75
ISSN: 0021-9517
DOI: 10.1016/j.jcat.2021.04.009
Popis: QM/MM calculations have been used to elucidate the reaction mechanism of the reduction of acetylene to ethylene catalyzed by a nitrogenase-like enzyme DCCPCh with an unusual [Fe8S9] double-cubane cluster. Various plausible reaction pathways, involving different oxidation states and protonation states of the iron-sulfur cluster, have been analyzed to find the most favorable one. The acetylene substrate bridges to the [Fe8S8] cluster via its triple bond in a μ-(bis-η2) coordination mode. After a proton-coupled electron transfer reduction of the reactant complex, the acetylene reduction may be described to proceed via a special “double-electron transfer induced proton transfer” mechanism, deduced from the principal interacting orbital analysis. The anti-ferromagnetically coupled [Fe8S8] cluster delivers a pair of α- and β-electrons to the substrate, concertedly but asynchronously with a proton transfer mediated by the second-shell Lys147 residue to one of the acetylene carbon atoms. Subsequently, the second proton-coupled electron transfer proceeds, followed by protonation of the substrate to afford the ethylene product. During the two-electron reaction, the oxidation states of the [Fe8S8] cluster cycle from [FeII6FeIII2], to [FeII7FeIII], to [FeII5FeIII3], and back to [FeII6FeIII2].
Databáze: OpenAIRE
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