Effect of Sodium Sulfide on Ni-Containing Carbon Monoxide Dehydrogenases

Journal Article · Wed Jul 28 04:00:00 EDT 2004 · Journal of the American Chemical Society

DOI:https://doi.org/10.1021/ja048811q· OSTI ID:826215

Feng, Jian ^[1]; Lindahl, Paul A

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1. Texas A&M University

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.

• Research Organization: Texas A& M University, College Station, TX (US)
• Sponsoring Organization: Office of Energy Research; basic biological sciences (US)
• DOE Contract Number: FG03-01ER15177
• OSTI ID: 826215
• Report Number(s): DOE/ER/15177-6
• Journal Information: Journal of the American Chemical Society, Journal Name: Journal of the American Chemical Society Journal Issue: 29 Vol. 126
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
ACETYL-COENZYME A SYNTHASE
ADDUCTS
ANIONS
CARBON MONOXIDE
CARBON MONOXIDE DEHYDROGENASE
CATALYSIS
DEHYDROGENATION
ENZYMES
EPR
NICKEL
IRON-SULFUR CLUSTERS
OXIDATION
OXIDOREDUCTASES
RHODOSPIRILLUM
SODIUM SULFIDES
SUBSTRATES
SULFIDE
SULFIDES