scholarly journals Fatty acids as modulators of cytochrome c oxidase in proteoliposomes

1996 ◽  
Vol 320 (2) ◽  
pp. 557-561 ◽  
Author(s):  
Martyn SHARPE ◽  
Ivano PERIN ◽  
John WRIGGLESWORTH ◽  
Peter NICHOLLS
Keyword(s):  
Fatty Acids ◽  
Enzyme Activity ◽  
Oleic Acid ◽  
Membrane Potential ◽  
Cytochrome C ◽  
Palmitic Acid ◽  
Cytochrome C Oxidase ◽  
Respiratory Control ◽  
Similar Concentration

The control of cytochrome c oxidase turnover in proteoliposomes by membrane potential (ΔΨ) and by pH gradient (ΔpH) is probably kinetic in nature, and inhibition by valinomycin and stimulation by nigericin indicate that ΔpH exerts a greater influence than does an equivalent ΔΨ. Oleic acid at 100 µM removes all ΔΨ and ΔpH control, whereas a similar concentration of palmitic acid increases turnover but does not completely abolish control. Valinomycin acts synergistically with both fatty acids, indicating that the latter can act as H+/K+ exchangers, but neither fatty acid alone markedly affects ΔpH, showing that they cannot fully mimic nigericin. Oleate, but not palmitate, diminishes ΔΨ, and can move electrophoretically as oleate anion. Submicromolar palmitic acid concentrations partly stimulate turnover in ΔΨ- and ΔpH-controlled proteoliposomes, as reported by Labonia, Muller and Azzi [(1988) Biochem. J. 254, 130–145], which might represent a direct effect on cytochrome c oxidase. The ubiquity of fatty acids in biological membranes suggests that these substances might be responsible for limiting respiratory control and enzyme activity in vivo.

scholarly journals The effect of non-esterified fatty acids on the proton-pumping cytochrome c oxidase reconstituted into liposomes

1988 ◽  
Vol 254 (1) ◽  
pp. 139-145 ◽  
Author(s):  
N Labonia ◽  
M Müller ◽  
A Azzi
Keyword(s):  
Fatty Acids ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Respiratory Control ◽  
Proton Pumping ◽  
Phospholipid Vesicles ◽  
Proton Permeability ◽  
Enzyme Preparations ◽  
Esterified Fatty Acids ◽  
Subunit Iii

Bovine heart cytochrome c oxidase was reconstituted in phospholipid vesicles, and the effect of different non-esterified fatty acids (NEFA) was studied on its proton pump and on the proton permeability of the vesicles. Neither parameter appeared to be affected by concentrations of NEFA known to uncouple oxidative phosphorylation (10 microM). Also the permeability for K+ was not affected by them. The fatty acids caused an increase in the rate of electron transfer in the absence, but not in the presence, of uncoupler and/or valinomycin [diminution of the respiratory-control index (RCI)]. The RCI of 8.7-7.5 was decreased to about 4.5 in the presence of 0.27-10 microM-NEFA. Oleic acid was not effective at the above concentrations. Subunit III-depleted enzyme preparations gave vesicles with an RCI of about 5.5, which was decreased to 4.5 in the presence of NEFA. With both native and subunit III-depleted oxidase the RCI was never decreased to the value of 1 by NEFA, as happens with classical protonophores.

Control of proteoliposomal cytochrome c oxidase: the overall reaction

1990 ◽  
Vol 68 (9) ◽  
pp. 1128-1134 ◽  
Author(s):  
Peter Nicholls ◽  
Chris E. Cooper ◽  
John M. Wrigglesworth
Keyword(s):  
Steady State ◽  
Membrane Potential ◽  
Cytochrome C ◽  
Cytochrome Oxidase ◽  
Cytochrome C Oxidase ◽  
Respiration Rate ◽  
Respiratory Control ◽  
Ph Gradient ◽  
Activity Levels ◽  
Simulation Programme

The control of cytochrome c oxidase incorporated into proteoliposomes has been investigated as a function of membrane potential (ΔΨ) and pH gradient (ΔpH). The oxidase generates a pH gradient (alkaline inside) and a membrane potential (negative inside) when respiring on external cytochrome c. Low levels of valinomycin collapse ΔΨ and increase ΔpH; the respiration rate decreases. High levels of valinomycin, however, decrease ΔpH as valinomycin can also act as a protonophore. Nigericin (in the absence of valinomycin) increases ΔΨ and collapses ΔpH; the respiration rate increases. On a millivolt equivalent basis ΔpH is a more effective inhibitor of activity than is ΔΨ. In the absence of any ionophores the cytochrome oxidase proteoliposomes enter a steady state, in which there are both ΔpH and ΔΨ components of control. Present and previous data suggest that the respiration rate responds in a linear way ("ohmically") to increasing ΔpH but in a nonlinear way to ΔΨ ("non-ohmically"). High levels of both ΔΨ and ΔpH do not completely inhibit turnover (maximal respiratory control values lie between 6 and 10). The controlled steady state involves the electrophoretic entry and electroneutral exit of K+ from the vesicles. A model is presented in which the enzyme responds to both ΔpH and ΔΨ components of the proton-motive force, but is more sensitive to ΔpH than to ΔΨ at an equivalent ΔμH+. The steady state of the proteoliposome system can be represented for any set of permeabilities and enzyme activity levels using the computer simulation programme Stella™.Key words: cytochrome c, cytochrome oxidase, proteoliposomes, respiratory control, modelling, valinomycin, nigericin.

Über eine in-vivo-Methode zur Herstellung radioaktiv markierter Phosphatide mit Sojabohnen / A Method for Preparing Radioactive Labeled Phosphatides Using Soybeans in-Vivo

1971 ◽  
Vol 26 (5) ◽  
pp. 425-434 ◽  
Author(s):  
J. Hölzl ◽  
H. Wagner
Keyword(s):  
Fatty Acids ◽  
Oleic Acid ◽  
Phosphatidic Acid ◽  
Stearic Acid ◽  
Palmitic Acid ◽  
De Novo ◽  
Specific Radioactivity ◽  
De Novo Synthesis ◽  
Experimental Conditions

Germinating soybeans, when incubated for 20-30 hours under an illumination at 25°-30° temp, with labeled 32P-phosphate, 14C-acetate, 14C-glycerol and 14C-choline, radioactivity ranging from 2 to 14% is incorporated into the main phosphatides lecithin (PC), phosphatidylethanolamine (PE) and monophosphoinositide (MPI). The incorporation of 32P-phosphate in these phosphatides depending on light and temperature, increases to its maximum (3.7 mCi/1 g soybeans) almost running linear and continues further even in the absence of any further germination due to intensive exposure to radiation.14C-acetate is incorporated almost exclusively into fatty acids of the phospholipids during germination as a result of which highest specific radioactivity was seen in the stearic acid followed by oleic acid and palmitic acid. Linol- and linolenic acid under these experimental conditions are weakly or not labeled, 14C-choline is incorporated only in PC. As the PC after 14C-(methyl) -methionine-incubation does not exhibit any significant labeling, one can exclude the pathway of PC-biosynthesis through PE-methylation. The utilization of 14C-glycerol proves that the incorporation of all the compounds under consideration here is effected not by a mere exchange but by a de novo synthesis. This procedure of labeling is suitable for preparing 3H-, 14C- and 32P-PC, -PE, -MPI and phosphatidic acid (PA).

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