Effect of Sodium Sulfide on Ni-Containing Carbon Monoxide Dehydrogenases

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OAK-B135 The structure of the active-site C-cluster in CO dehydrogenase from Carboxythermus hydrogenoformans includes a {mu}{sup 2}-sulfide ion bridged to the Ni and unique Fe, while the same cluster in enzymes from Rhodospirillum rubrum (CODH{sub Rr}) and Moorella thermoacetica (CODH{sub Mt}) lack this ion. This difference was investigated by exploring the effects of sodium sulfide on activity and spectral properties. Sulfide partially inhibited the CO oxidation activity of CODH{sub Rr} and generated a lag prior to steady-state. CODH{sub Mt} was inhibited similarly but without a lag. Adding sulfide to CODH{sub Mt} in the C{sub red1} state caused the g{sub av} ... continued below

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33 pages

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Feng, Jian & Lindahl, Paul A. July 28, 2004.

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  • Texas A & M University
    Publisher Info: Texas A&M University, College Station, TX (United States)
    Place of Publication: College Station, Texas

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OAK-B135 The structure of the active-site C-cluster in CO dehydrogenase from Carboxythermus hydrogenoformans includes a {mu}{sup 2}-sulfide ion bridged to the Ni and unique Fe, while the same cluster in enzymes from Rhodospirillum rubrum (CODH{sub Rr}) and Moorella thermoacetica (CODH{sub Mt}) lack this ion. This difference was investigated by exploring the effects of sodium sulfide on activity and spectral properties. Sulfide partially inhibited the CO oxidation activity of CODH{sub Rr} and generated a lag prior to steady-state. CODH{sub Mt} was inhibited similarly but without a lag. Adding sulfide to CODH{sub Mt} in the C{sub red1} state caused the g{sub av} = 1.82 EPR signal to decline and new features to appear, including one with g = 1.95, 1.85 and (1.70 or 1.62). Removing sulfide caused the g{sub av} = 1.82 signal to reappear and activity to recover. Sulfide did not affect the g{sub av} = 1.86 signal from the C{sub red2} state. A model was developed in which sulfide binds reversibly to C{sub red1}, inhibiting catalysis. Reducing this adduct causes sulfide to dissociate, C{sub red2} to develop, and activity to recover. Using this model, apparent K{sub I} values are 40 {+-} 10 nM for CODH{sub Rr} and 60 {+-} 30 {micro}M for CODH{sub Mt}. Effects of sulfide are analogous to those of other anions, including the substrate hydroxyl group, suggesting that these ions also bridge the Ni and unique Fe. This proposed arrangement raises the possibility that CO binding labilizes the bridging hydroxyl and increases its nucleophilic tendency towards attacking Ni-bound carbonyl.

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33 pages

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OSTI as DE00826215

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  • Journal Name: Journal of the American Chemical Society; Journal Volume: 126; Journal Issue: 29; Other Information: Published in Journal of the American Chemical Society, Volume 126, No.29; DOI 10.1021/ja048811q

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  • Report No.: DOE/ER/15177-6
  • Grant Number: FG03-01ER15177
  • DOI: 10.1021/ja048811q | External Link
  • Office of Scientific & Technical Information Report Number: 826215
  • Archival Resource Key: ark:/67531/metadc780863

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  • July 28, 2004

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  • Dec. 3, 2015, 9:30 a.m.

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  • May 6, 2016, 2:13 p.m.

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Feng, Jian & Lindahl, Paul A. Effect of Sodium Sulfide on Ni-Containing Carbon Monoxide Dehydrogenases, article, July 28, 2004; College Station, Texas. (digital.library.unt.edu/ark:/67531/metadc780863/: accessed August 23, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.