scholarly journals Thermodynamic and steady-state-kinetic investigation of the effect of NN′-dicyclohexylcarbodi-imide on H+ translocation by the mitochondrial cytochrome bc1 complex

1985 ◽  
Vol 225 (2) ◽  
pp. 407-411 ◽  
Author(s):  
M D Brand ◽  
M K Al-Shawi ◽  
G C Brown ◽  
B D Price
Keyword(s):  
Steady State ◽  
Thermodynamic Assessment ◽  
Cytochrome Bc1 ◽  
Kinetic Investigation ◽  
Bc1 Complex ◽  
Cytochrome Bc1 Complex ◽  
Kinetic Measurements ◽  
Steady State Kinetic ◽  
Force Ratio ◽  
State Kinetic

Steady-state kinetic measurements showed that NN′-dicyclohexylcarbodi-imide decreased the observed H+/2e ratio of H+ transport by mitochondria respiring on succinate, acting mainly at the cytochrome bc1 complex. Thermodynamic assessment of the H+/2e ratio by measuring the force ratio across the bc1 complex showed that the inhibitor did not affect H+ translocation. Possible explanations of this disagreement between methods are examined; we conclude that the inhibitor does not alter the mechanistic stoichiometry of H+ pumping by the bc1 complex.

scholarly journals Thermodynamic control of electron flux through mitochondrial cytochrome bc1 complex

1985 ◽  
Vol 225 (2) ◽  
pp. 399-405 ◽  
Author(s):  
G C Brown ◽  
M D Brand
Keyword(s):  
Liver Mitochondria ◽  
Cytochrome Bc1 ◽  
Rat Liver Mitochondria ◽  
Protonmotive Force ◽  
Bc1 Complex ◽  
Thermodynamic Control ◽  
Cytochrome Bc1 Complex ◽  
Redox States ◽  
Force Ratio ◽  
Carbonyl Cyanide

The redox states of exogenously added ubiquinone-2 and cytochrome c, and the protonmotive force (delta p) of rat liver mitochondria were measured as the respiration rate was titrated with the uncoupler carbonyl cyanide p-trifluoromethoxyphenyl-hydrazone. The force ratio delta Eh/delta p across the bc1 complex was close to 1:1 in State 4, indicating an H+/e- stoichiometry of 1:1 for the cytochrome bc1 complex, excluding protons moved by pool ubiquinone. Assuming a constant stoichiometry the rate of electron transport increased linearly with the disequilibrium (delta Eh - delta p) across the complex.

scholarly journals Pre-steady-state kinetic investigation of bypass of a bulky guanine lesion by human Y-family DNA polymerases

DNA Repair ◽  
2016 ◽  
Vol 46 ◽  
pp. 20-28 ◽  
Author(s):  
E. John Tokarsky ◽  
Varun V. Gadkari ◽  
Walter J. Zahurancik ◽  
Chanchal K. Malik ◽  
Ashis K. Basu ◽  
...  
Keyword(s):  
Steady State ◽  
Dna Polymerases ◽  
Kinetic Investigation ◽  
Steady State Kinetic ◽  
Y Family ◽  
State Kinetic

scholarly journals Dihydrolipoamide dehydrogenase from halophilic archaebacteria

1984 ◽  
Vol 218 (3) ◽  
pp. 811-818 ◽  
Author(s):  
M J Danson ◽  
R Eisenthal ◽  
S Hall ◽  
S R Kessell ◽  
D L Williams
Keyword(s):  
Steady State ◽  
Iodoacetic Acid ◽  
Enzymic Activity ◽  
Evolutionary Significance ◽  
Dihydrolipoamide Dehydrogenase ◽  
Kinetic Measurements ◽  
Steady State Kinetic ◽  
Halophilic Archaebacteria ◽  
Eukaryotic Organisms ◽  
State Kinetic

Dihydrolipoamide dehydrogenase has been discovered in the halophilic archaebacteria for the first time. The enzyme from both classical and alkaliphilic halobacteria has been investigated. (1) The enzyme specifically catalysed the stoichiometric oxidation of dihydrolipoamide by NAD+. Enzymic activity was optimal at 2 M-NaCl and was remarkably resistant to thermal denaturation. (2) The relative molecular masses (Mr) of the native enzyme from the various species of halobacteria were determined to be within the range 112000-120000. (3) The enzyme exhibited a hyperbolic dependence of catalytic activity on both dihydrolipoamide and NAD+ concentrations. From these steady-state kinetic measurements the dissociation constant (Ks) of dihydrolipoamide was determined to be 57 (+/- 5) microM. (4) The enzyme was only susceptible to inactivation by iodoacetic acid in the presence of its reducing ligands, dihydrolipoamide or NADH. The rate of inactivation followed a hyperbolic dependence on the concentration of dihydrolipoamide, from which the Ks of this substrate was calculated to be 55 (+/- 7) microM. Together with the steady-state kinetic data, the pattern of inactivations is consistent with the involvement in catalysis of a reversibly reducible disulphide bond, as has been found in dihydrolipoamide dehydrogenase from non-archaebacterial species. In eubacterial and eukaryotic organisms, dihydrolipoamide dehydrogenase functions in the 2-oxo acid dehydrogenase complexes. These multienzyme systems have not been detected in the archaebacteria, and, in the context of this apparent absence, the possible function and evolutionary significance of archaebacterial dihydrolipoamide dehydrogenase are discussed.

Steady-State Kinetic Investigation of Cytochrome P450cam:  Interaction with Redox Partners and Reaction with Molecular Oxygen†

Biochemistry ◽  
2004 ◽  
Vol 43 (1) ◽  
pp. 271-281 ◽  
Author(s):  
Matthew M. Purdy ◽  
Laura S. Koo ◽  
Paul R. Ortiz de Montellano ◽  
Judith P. Klinman
Keyword(s):  
Steady State ◽  
Molecular Oxygen ◽  
Kinetic Investigation ◽  
Cytochrome P450cam ◽  
Redox Partners ◽  
Steady State Kinetic ◽  
State Kinetic
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