期刊
DALTON TRANSACTIONS
卷 40, 期 20, 页码 5516-5527出版社
ROYAL SOC CHEMISTRY
DOI: 10.1039/c1dt10240k
关键词
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资金
- NCI National Facility at the Australian National University
- University of New South Wales
Nitrogenase enzymes containing molybdenum normally reduce N(2) to NH(3), and are severely inhibited by CO, but vanadium-nitrogenase reduces CO to hydrocarbons C(2)H(4), C(2)H(6) and C(3)H(8). Aspects of the mechanism of this unexpected and unprecedented reaction have been investigated by density functional simulations of the iron-vanadium cofactor FeV-co [NFe(7)VS(9)(homocitrate)] protein-bound by cysteine and histidine. It is found that the intramolecular hydrogenating machinery previously proposed for N(2) reduction (including H-atom tunneling) can also effect reduction of CO. There are feasible steps for all of the requisite components of the overall reaction, namely (i) the binding of CO, (ii) the initial hydrogenation of CO to HCO, (iii) continued hydrogenations of CO at both C and O to HCOH and H(2)COH, (iv) eliminations of O as H(2)O, and (v) the C-C bond formation steps. Intermediate organic fragments can migrate around the active face of FeV-co, and hydrogen bonding between COH functions and S or SH components of FeV-co can occur and contribute to the stabilisation and orientation of intermediates. It is suggested that the difference between Mo-nitrogenase and V-nitrogenase occurs in the immediately surrounding protein, which facilitates (possibly via water associated with homocitrate bound to V) the exogenous protonation and dehydration of -COH intermediates.
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