The Correlation of Redox Potential, HOMO Energy, and Oxidation State in Metal Sulfide Clusters and Its Application to Determine the Redox Level of the FeMo-co Active-Site Cluster of Nitrogenase

2006 ◽  
Vol 45 (13) ◽  
pp. 5084-5091 ◽  
Author(s):  
Ian Dance
Keyword(s):  
Redox Potential ◽  
Oxidation State ◽  
Active Site ◽  
Metal Sulfide ◽  
Homo Energy ◽  
Site Cluster ◽  
Sulfide Clusters ◽  
Redox Level

scholarly journals Oxidation-State-Dependent Binding Properties of the Active Site in a Mo-Containing Formate Dehydrogenase

2017 ◽  
Vol 139 (29) ◽  
pp. 9927-9936 ◽  
Author(s):  
William E. Robinson ◽  
Arnau Bassegoda ◽  
Erwin Reisner ◽  
Judy Hirst
Keyword(s):  
Oxidation State ◽  
Active Site ◽  
Formate Dehydrogenase ◽  
Binding Properties ◽  
State Dependent

scholarly journals Converting the NiFeS Carbon Monoxide Dehydrogenase to a Hydrogenase and a Hydroxylamine Reductase

2002 ◽  
Vol 184 (21) ◽  
pp. 5894-5897 ◽  
Author(s):  
Jongyun Heo ◽  
Marcus T. Wolfe ◽  
Christopher R. Staples ◽  
Paul W. Ludden
Keyword(s):  
Carbon Monoxide ◽  
Amino Acid ◽  
Active Site ◽  
Reductase Activity ◽  
Carbon Monoxide Dehydrogenase ◽  
Hydrogenase Activity ◽  
Uptake Hydrogenase ◽  
Site Cluster ◽  
Metal Ligand

ABSTRACT Substitution of one amino acid for another at the active site of an enzyme usually diminishes or eliminates the activity of the enzyme. In some cases, however, the specificity of the enzyme is changed. In this study, we report that the changing of a metal ligand at the active site of the NiFeS-containing carbon monoxide dehydrogenase (CODH) converts the enzyme to a hydrogenase or a hydroxylamine reductase. CODH with alanine substituted for Cys531 exhibits substantial uptake hydrogenase activity, and this activity is enhanced by treatment with CO. CODH with valine substituted for His265 exhibits hydroxylamine reductase activity. Both Cys531 and His265 are ligands to the active-site cluster of CODH. Further, CODH with Fe substituted for Ni at the active site acquires hydroxylamine reductase activity.

scholarly journals Interaction of Potassium Cyanide with the [Ni-4Fe-5S] Active Site Cluster of CO Dehydrogenase fromCarboxydothermus hydrogenoformans

2007 ◽  
Vol 282 (14) ◽  
pp. 10639-10646 ◽  
Author(s):  
Seung-Wook Ha ◽  
Malgorzata Korbas ◽  
Mirjam Klepsch ◽  
Wolfram Meyer-Klaucke ◽  
Ortwin Meyer ◽  
...  
Keyword(s):  
Active Site ◽  
Potassium Cyanide ◽  
Co Dehydrogenase ◽  
Site Cluster

scholarly journals Unusual behaviour of perflurorinated cobalt phthalocyanine compared to unsubstituted cobalt phthalocyanine for the electrocatalytic oxidation of hydrazine. Effect of the surface concentration of the catalyst on the graphite surface

2013 ◽  
Vol 78 (12) ◽  
pp. 2039-2052 ◽  
Author(s):  
José Zagal ◽  
Daniela Geraldo ◽  
Mamie Sancy ◽  
Maritza Paez
Keyword(s):  
Redox Potential ◽  
Active Site ◽  
Electrocatalytic Oxidation ◽  
Graphite Electrode ◽  
Surface Concentration ◽  
Cobalt Phthalocyanine ◽  
Peak Potential ◽  
Formal Potential ◽  
Single Complex ◽  
Site Versus

We have found that CoPc and 16(F)CoPc when adsorbed on graphite electrode exhibit voltammograms in alkaline solution (0.2M NaOH) that show the typical redox peaks attributed to the Co(II)/(I) reversible. The peak potential for CoPc is independent of surface concentration of the catalyst. In contrast, for 16(F)CoPc the Co(II)/(I) redox process shifts to more negative potentials when the surface concentration of the catalyst increases. In a volcano correlation of log (i/G)E (activity per active site) versus Co (II)/(I) formal potential of catalyst (using several CoN4 chelates) CoPc appears in the ascending portion (activity increases with the Co (II)/(I) redox potential) whereas 16(F)CoPc appears in the region where activity decreases with the redox potential. In a plot of log (i/G)E versus the Co(II)/(I) formal potential of 16(F)CoPc the declining portion of the volcano is reproduced for one single complex. So 16(F)CoPc at different surface concentrations behaves as Co complexes having different redox potential in the declining portion of the volcano plot, when the activity is normalized for the surface concentration. This is not observed for CoPc.

Ca2+ stabilizes the semiquinone radical of pyrroloquinoline quinone

2001 ◽  
Vol 357 (3) ◽  
pp. 893-898 ◽  
Author(s):  
Akihiro SATO ◽  
Kazuyoshi TAKAGI ◽  
Kenji KANO ◽  
Nobuo KATO ◽  
Johannis A. DUINE ◽  
...  
Keyword(s):  
Redox Potential ◽  
Active Site ◽  
Continuous Flow ◽  
Glucose Dehydrogenase ◽  
Acinetobacter Calcoaceticus ◽  
Substrate Oxidation ◽  
Pyrroloquinoline Quinone ◽  
Free State ◽  
Semiquinone Radical ◽  
Chemical Mechanisms

Spectroelectrochemical studies were performed on the interaction between Ca2+ and pyrroloquinoline quinone (PQQ) in soluble glucose dehydrogenase (sGDH) and in the free state by applying a mediated continuous-flow column electrolytic spectroelectrochemical technique. The enzyme forms used were holo-sGDH (the holo-form of sGDH from Acinetobacter calcoaceticus) and an incompletely reconstituted form of this, holo-X, in which the PQQ-activating Ca2+ is lacking. The spectroelectrochemical and ESR data clearly demonstrated the generation of the semiquinone radical of PQQ in holo-sGDH and in the free state in the presence of Ca2+. In contrast, in the absence of Ca2+ no semiquinone was observed, either for PQQ in the free state (at pH7.0) or in the enzyme (holo-X). Incorporation of Ca2+ into the active site of holo-X, yielding holo-sGDH, caused not only stabilization of the semiquinone form of PQQ but also a negative shift (of 26.5mV) of the two-electron redox potential, indicating that the effect of Ca2+ is stronger on the oxidized than on the reduced PQQ. Combining these data with the observations on the kinetic and chemical mechanisms, it was concluded that the strong stimulating effect of Ca2+ on the activity of sGDH can be attributed to facilitation of certain kinetic steps, and not to improvement of the thermodynamics of substrate oxidation. The consequences of this conclusion are discussed for the oxidative as well as for the reductive part of the reaction of sGDH.

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