scholarly journals Modulation of cytochrome oxidase activity by inorganic and organic phosphate

1987 ◽  
Vol 248 (1) ◽  
pp. 161-165 ◽  
Author(s):  
F Malatesta ◽  
G Antonini ◽  
P Sarti ◽  
M Brunori
Keyword(s):  
Ionic Strength ◽  
Cytochrome C ◽  
Cytochrome Oxidase ◽  
Oxidase Activity ◽  
Respiratory Control ◽  
Organic Phosphate ◽  
Phospholipid Vesicles ◽  
Respiratory Control Ratio ◽  
Phospholipid Membrane ◽  
Ferrocytochrome C

The activity of cytochrome oxidase reconstituted into phospholipid vesicles has been studied as a function of orthophosphate, ATP and inositol hexakisphosphate concentrations. The respiratory-control ratio was found to be quite sensitive to these compounds and was inversely related to the anion concentration. This effect is related to a phosphate-dependent decrease in the rate constant for ferrocytochrome c oxidation observed in the presence of ionophores. The data cannot be interpreted simply on the basis of ionic strength, which is known to limit cytochrome c binding to cytochrome oxidase, since cytochrome oxidase-containing vesicles responded differently to phosphate depending on the energization state of the phospholipid membrane.

scholarly journals Effects of detergents and cytochrome c binding on scalar and vectorial proton ejection by proteoliposomes containing cytochrome oxidase

1985 ◽  
Vol 228 (1) ◽  
pp. 201-210 ◽  
Author(s):  
P Nicholls ◽  
S Shaughnessy
Keyword(s):  
Ionic Strength ◽  
Cytochrome C ◽  
Respiratory Control ◽  
Ferrocytochrome C ◽  
Carbonyl Cyanide ◽  
Low Levels ◽  
Low Ionic Strength ◽  
Catalytic Functions ◽  
Narrow Concentration Range ◽  
Lipid Micelles

The detergent lauryl maltoside abolishes respiratory control and proton ejection by cytochrome c oxidase-containing proteoliposomes over a narrow concentration range. Expression of cryptic activity (inward-facing oxidase) is released over the same concentration range. Catalytic functions (Vmax. and Km) of the enzyme are not changed by the detergent. Lipid micelles containing detergent bind approximately the same amount of cytochrome c as do vesicles containing an equivalent amount of lipid. Uncoupler-insensitive proton release is seen when proteoliposomes are pulsed with ferrocytochrome c at low ionic strength. Such uncoupler-insensitive acidification is not seen at higher ionic strength, nor with oxygen pulses of anaerobic solutions previously incubated with cytochrome c. Vesicles at low ionic strength catalyse cytochrome c autoxidation; this process can mimic proton re-equilibration in systems that have pumped protons from inside to the bulk phase. Proton re-equilibration following a pulse of cytochrome c or oxygen is multiphasic. The slowest phases are attributed to vesicle heterogeneity, some internal alkali being retained within vesicles of low intrinsic proton permeability. This can be overcome by the addition of either very low levels of carbonyl cyanide p-trifluoromethoxyphenyl-hydrazone or high levels of valinomycin.

Optimum pH and ionic strength for the assay of cytochrome c oxidase from pea cotyledon mitochondria

1977 ◽  
Vol 55 (10) ◽  
pp. 1114-1117 ◽  
Author(s):  
Gerrit H. Bomhoff ◽  
Mary Spencer
Keyword(s):  
Ionic Strength ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Ferrocytochrome C ◽  
Optimum Ph ◽  
Triton X ◽  
Assay Conditions ◽  
Nonionic Detergents

Cytochrome c oxidase (EC 1.9.3.1) has been solubilized by use of the nonionic detergents Triton X-114 and Triton X-100, from pea cotyledon mitochondria. Optimum assay conditions were determined for the oxidation of ferrocytochrome c in air. The results indicate that the plant cytochrome c oxidase resembles mammalian preparations in its sensitivity towards ionic strength and pH of the assay buffer.

Reduction of Cytochrome c by Tetrathionate in the Presence of Tetrathionate Hydrolase Purified from Sulfur-Grown Acidithiobacillus Ferrooxidans ATCC 23270

2009 ◽  
Vol 71-73 ◽  
pp. 243-246
Author(s):  
Taher M. Taha ◽  
Fumiaki Takeuchi ◽  
Tsuyoshi Sugio
Keyword(s):  
Cytochrome C ◽  
Cytochrome Oxidase ◽  
Acidithiobacillus Ferrooxidans ◽  
Oxidase Activity ◽  
Elemental Sulfur ◽  
Enzyme System ◽  
Size Exclusion ◽  
Ammonium Sulfate Precipitation ◽  
Interesting Phenomenon ◽  
Oxidase Enzyme

It is mysterious that, when A. ferrooxidans ATCC 23270 cells grow on elemental sulfur, they have high iron oxidase activity comparable to that of iron-grown cells as well as high activities of sulfide:ferric ion oxidoreductase (SFORase) and tetrathionate hydrolase. To clarify this interesting phenomenon, cytochrome c and tetrathionate hydrolase were purified from sulfur-grown A. ferrooxidans cells using ammonium sulfate precipitation, Phenyl column chromatography, and SuperdexTM 75 and Sephadex G-100 size exclusion column chromatographies. The purified cytochrome c was reduced by tetrathionate in the presence of purified tetrathionate hydrolase, but not in the absence of the enzyme. When the partially purified cytochrome c fraction containing aa3-type cytochrome oxidase was used, both cytochrome c and aa3-type cytochrome oxidase were reduced by tetrathionate in the presence of purified tetrathionate hydrolase. These results indicate that tetrathionate in the presence of tetrathionate hydrolase can reduce iron oxidase enzyme system containing cytochrome c and aa3-type cytochrome oxidase as tetrathionate hydrolase decomposes tetrathionate to produce thiosulfate, elemental sulfur, and sulfate; and the formed thiosulfate can chemically reduce cytochrome c and Fe3+.

scholarly journals Reconstitution of cytochrome c oxidase in phospholipid vesicles containing polyvinylic polymers

1989 ◽  
Vol 257 (3) ◽  
pp. 783-787 ◽  
Author(s):  
P Sarti ◽  
G Antonini ◽  
F Malatesta ◽  
B Vallone ◽  
S Villaschi ◽  
...  
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Functional Characterization ◽  
Respiratory Control ◽  
Phospholipid Vesicles ◽  
Lipid Phase ◽  
Protein Orientation ◽  
Highly Hydrophobic ◽  
Polymer Interaction

Cytochrome c oxidase was reconstituted in phospholipid vesicles in the presence of highly hydrophobic poly(vinyl alkanoate) polymers. Electron-microscopy observations demonstrated that polymer interaction with the lipid phase induces vesicles to adopt smaller diameters than those typical of standard proteoliposomes. Functional characterization of these polymer-proteoliposome structures indicates that the reconstitution of the enzyme proceeds efficiently without causing either scrambling of the protein orientation in the membrane or loss of respiratory control. A clear dependence of respiratory control ratio on vesicle size was also demonstrated, which is in agreement with a previous model proposed for control of activity of cytochrome c oxidase vesicles [Brunori, Sarti, Colosimo, Antonini, Malatesta, Jones & Wilson (1985) EMBO J. 4, 2365-2368].

Kinetics of oxidation of reduced cytochrome c by aquacopper(II) and chlorocopper(II) complexes in the presence of oxygen

1981 ◽  
Vol 34 (1) ◽  
pp. 99 ◽  
Author(s):  
JK Yandell
Keyword(s):  
Reaction Mechanism ◽  
Ionic Strength ◽  
Cytochrome C ◽  
Rate Constants ◽  
Kinetics Of Oxidation ◽  
Ferrocytochrome C ◽  
Kinetics Of

The rate constants for the oxidation of reduced cytochrome c by aquacopper(II) ion, aquachloro- copper(II) ion and aquadichlorocopper(II) were found to be 5.7�0.3 1. mol-1 s-1, 2.3×102 1. mol-1 s-1 and 5.6xl031. mol-1 s-1 respectively at 25�C, ionic strength 0.1 and pH 4.0. At low ratios of aquacopper(II) ion to ferrocytochrome c, when oxygen is required to completely oxidize the cytochrome, the reaction mechanism was found to be complex. No evidence for the involvement of copper bound to the cytochrome was found.

CYTOCHROME OXIDASE ACTIVITY OF CELL NUCLEI

1954 ◽  
Vol 32 (1) ◽  
pp. 548-552 ◽  
Author(s):  
David Rubinstein ◽  
Orville F. Denstedt
Keyword(s):  
Cytochrome C ◽  
Cytochrome Oxidase ◽  
Oxidase Activity ◽  
Nuclear Material ◽  
Liver Cells ◽  
Nuclear Fraction ◽  
Cell Nuclei ◽  
Nuclear Membranes ◽  
Rat Liver Cells ◽  
Chicken Erythrocytes

The presence of cytochrome oxidase in the nuclear material from chicken erythrocytes and rat-liver cells has been demonstrated with the aid of p-phenylenediamine as the agent for reducing cytochrome c. The three reagents p-phenylenediamine, ascorbate, and hydroquinone are effective in the estimation of cytochrome oxidase in mitochondrial preparations, but only the first mentioned agent can effect the reduction of endogenous cytochrome c. The addition of cytochrome c will increase the oxidase activity of the liver-cell mitochondria but not of the nuclear fraction from the erythrocytes or the liver cells, presumably because of the impermeability of the nuclear membranes to added cytochrome c.

scholarly journals Studies on partially reduced mammalian cytochrome oxidase reactions with ferrocytochrome c

1976 ◽  
Vol 157 (3) ◽  
pp. 591-598 ◽  
Author(s):  
C Greenwood ◽  
T Brittain
Keyword(s):  
Electron Transfer ◽  
Cytochrome C ◽  
Cytochrome Oxidase ◽  
Transfer Reaction ◽  
Temperature Jump ◽  
Electron Transfer Reaction ◽  
Relaxation Processes ◽  
Stopped Flow ◽  
Rapid Reduction ◽  
Ferrocytochrome C

The kinetics of the electron-transfer process which occurs between ferrocytochrome c and partially reduced mammalian cytochrome oxidase were studied by the rapid spectrophotometric techniques of stopped flow and temperature jump. Stopped-flow experiments showed initial very fast extinction changes at 605 nm and at 563 nm, indicating the simultaneous reduction of cytochrome a and oxidation of ferrocytochrome c. During this ‘burst’ phase, say the first 50 ms after mixing, it was invariably found that more cytochrome c had been oxidized than cytochrome a had been reduced. This discrepancy in electron equivalents may be accounted for by the rapid reduction of another redox site in the enzyme, possibly that associated with the extinction changes observed at 830 nm. During the incubation period in which the partially reduced oxidase was prepared, the rate of reduction of cytochrome a by ferrocytochrome c, at constant reactant concentrations, decreased with time. Temperature-jump experiments showed the presence of two relaxation processes. The faster of the two phases was assigned to the electron-transfer reaction between cytochrome c and cytochrome a. A study of the concentration-dependence of the reciprocal relaxation time for this phase yielded a rate constant of 9 X 10(6)M-1-s-1 for the electron transfer from cytochrome c to cytochrome a, and a value of 8.5 X 10(6)M-1-s-1 for the reverse reaction. The equilibrium constant for the electron-transfer reaction is therefore close to unity. The slower phase has been interpreted as signalling the transfer of electrons between cytochrome a and another redox site within the oxidase molecule.

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