Effect of NAD and Rotenone on the Partitioning of Malate Oxidation Between Malate Dehydrogenase and Malic Enzyme in Isolated Plant Mitochondria

1985 ◽  
Vol 12 (3) ◽  
pp. 229 ◽  
Author(s):  
JH Bryce ◽  
JT Wiskich
Keyword(s):  
Energy Metabolism ◽  
Electron Transport ◽  
Oxygen Uptake ◽  
Malate Dehydrogenase ◽  
Malic Enzyme ◽  
Plant Mitochondria ◽  
Metabolizing Enzyme ◽  
Stimulation Of ◽  
Malate Metabolism ◽  
Malate Oxidation

Our aim was to determine whether there is a specific link between NAD-malic enzyme and the rotenone- insensitive bypass of electron transport. Mitochondria were isolated from fresh beetroot tissue, aged beetroot slices, and turnips. Oxygen uptake and pyruvate production were measured in reactions where these mitochondria were metabolizing malate at pH 6.8 in the presence of glutamate, to facilitate the removal of oxaloacetate, and in its absence. In the absence of glutamate there was substantial activity of malic enzyme. NAD+ (577 �M) prevented a fall in oxygen uptake by stimulating malic enzyme. Rotenone (19 �M) reduced oxygen uptake. This inhibited rate was stimulated by NAD+ due, in particular, to a stimulation of malic enzyme. We conclude that the stimulation of malate metabolism by NAD+ is accounted for by malic enzyme due to the unfavourable equilibrium of malate dehydrogenase for malate oxidation and the resultant accumulation of oxaloacetate, and not to any specific link between malic enzyme and the rotenone-insensitive bypass. In the presence of glutamate, malate dehydrogenase was the predominant malate metabolizing enzyme. Oxygen uptake and malic enzyme were stimulated and inhibited by NAD+ and rotenone, respectively. In the presence of rotenone, NAD+ stimulated oxygen uptake and increased the percentage due to malic enzyme. This stimulation is accounted for by the higher Kin of the rotenone-insensitive dehydrogenase for NADH and the unfavourable equilibrium position of malate dehydrogenase resulting in activation of malic enzyme only. We conclude that malic enzyme is not specifically linked to the rotenone-insensitive pathway of electron transport. This has important implications for the regulation of energy metabolism in plants.

Pyruvate carboxylation prevents the decline in contractile function of rat hearts oxidizing acetoacetate

1991 ◽  
Vol 261 (6) ◽  
pp. H1756-H1762 ◽  
Author(s):  
R. R. Russell ◽  
H. Taegtmeyer
Keyword(s):  
Malate Dehydrogenase ◽  
Malic Enzyme ◽  
Contractile Function ◽  
Tricarboxylic Acid Cycle ◽  
Pyruvate Carboxylation ◽  
Physiological Importance ◽  
Rat Hearts ◽  
Stable Performance ◽  
And Function ◽  
Malate Oxidation

Acetoacetate, when present as the only fuel for respiration in rat hearts, causes an impairment in contractile function that is reversible with the addition of substrates that can contribute to anaplerosis. To determine the importance of pyruvate carboxylation via NADP(+)-dependent malic enzyme on metabolism and function in hearts oxidizing acetoacetate, isolated working rat hearts were perfused with [1-14C]pyruvate and acetoacetate. While the cardiac power output after 60 min of perfusion in hearts utilizing acetoacetate alone had fallen to 44% of the initial value, the addition of pyruvate resulted in a stable performance with no fall in the work output. When hydroxymalonate, an inhibitor of NADP(+)-dependent malic enzyme and malate dehydrogenase, was added to the two substrates, function at 60 min was similar to the value for hearts oxidizing acetoacetate alone. Measurements of the specific activities of malate, aspartate, and citrate confirm inhibition of both pyruvate carboxylation and malate oxidation. The findings are consistent with a mechanism in which the enrichment of malate by pyruvate improves function by increasing the production of reducing equivalents by the malate dehydrogenase and the isocitrate dehydrogenase reactions increase flux through the span of the tricarboxylic acid cycle from malate to 2-oxoglutarate. The present study demonstrates the physiological importance of anaplerotic pathways in maintaining contractile function in the heart.

scholarly journals Interaction of Benzylaminopurine with Electron Transport in Plant Mitochondria during Malate Oxidation

1983 ◽  
Vol 73 (4) ◽  
pp. 945-948 ◽  
Author(s):  
Michèle Chauveau ◽  
Pierre Dizengremel ◽  
Jean Roussaux
Keyword(s):  
Electron Transport ◽  
Plant Mitochondria ◽  
Malate Oxidation

Respiration and carbohydrate energy metabolism of the lung-dwelling parasite Rhabdias bufonis (Nematoda: Rhabdiasoidea)

Parasitology ◽  
1978 ◽  
Vol 76 (1) ◽  
pp. 21-27 ◽  
Author(s):  
A. O. Anya ◽  
G. M. Umezurike
Keyword(s):  
Lactate Dehydrogenase ◽  
Energy Metabolism ◽  
Malate Dehydrogenase ◽  
Malic Enzyme ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Weight Basis ◽  
Fresh Weight ◽  
Fresh Weight Basis ◽  
Alternative Pathways

SummaryAn investigation of the carbohydrate energy metabolism of Rhabdias bufonis, the lung-dwelling nematode parasite of the African toad, Bufo regularis, indicates that the nematode stores very little glycogen (0·137 ± 0·003% on a fresh weight basis) but does utilize oxygen in vitro. The intracellular distribution and high levels of activity observed for the enzymes phosphoenolpyruvate carboxykinase, pyruvate kinase, lactate dehydrogenase, malate dehydrogenase, malic enzyme and fumarate reductase suggest two alternative pathways of carbohydrate energy metabolism.

Arsenate Uncoupling of Oxidative Phosphorylation in Isolated Plant Mitochondria

1976 ◽  
Vol 3 (2) ◽  
pp. 153 ◽  
Author(s):  
W.A Wickes ◽  
J.T Wiskish
Keyword(s):  
Electron Transfer ◽  
Oxidative Phosphorylation ◽  
Plant Mitochondria ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Transfer Processes ◽  
Uncoupling Of Oxidative Phosphorylation ◽  
Electron Transfer Processes ◽  
Stimulation Of ◽  
Malate Oxidation

The uncoupling by arsenate of beetroot and cauliflower bud mitochondria showed the following characteristics: (1) arsenate stimulation of respiration above the rate found with phosphate; (2) inhibition of arsenate-stimulated respiration by phosphate; (3) enhancement of arsenate-stimulated respiration by ADP; (4) only partial prevention of this ADP-enhanced respiration by atractyloside; (5) inhibition by oligomycin of the arsenate-stimulated respiration back to the phosphate rate; and (6) the absence of any stimulatory effect of ADP in the presence of oligomycin. These results are qualitatively analogous to those reported for arsenate uncoupling in rat liver mitochondria. Arsenate stimulated malate oxidation, presumably by stimulating malate entry, in both beetroot and cauliflower bud mitochondria; however, high rates of oxidation, and presumably entry, were only sustained with arsenate in beetroot mitochondria. NADH was oxidized rapidly in cauliflower bud mitochondria in the presence of arsenate, showing that arsenate did not inhibit electron transfer processes.

scholarly journals Succinate-driven reverse electron transport in the respiratory chain of plant mitochondria. The effects of rotenone and adenylates in relation to malate and oxaloacetate metabolism

1991 ◽  
Vol 274 (1) ◽  
pp. 249-255 ◽  
Author(s):  
P Rustin ◽  
C Lance
Keyword(s):  
Electron Transport ◽  
Succinate Dehydrogenase ◽  
Malate Dehydrogenase ◽  
Electron Flow ◽  
Plant Mitochondria ◽  
Inhibitory Effect ◽  
Experimental Conditions ◽  
Dehydrogenase Reaction ◽  
The Matrix ◽  
Reverse Electron Transport

The effects of rotenone on the succinate-driven reduction of matrix nicotinamide nucleotides were investigated in Percoll-purified mitochondria from potato (Solanum tuberosum) tubers. Depending on the presence of ADP or ATP, rotenone caused an increase or a decrease in the level of reduction of the matrix nicotinamide nucleotides. The increase in the reduction induced by rotenone in the presence of ADP was linked to the oxidation of the malate resulting from the oxidation of succinate. Depending on the experimental conditions, malic enzyme (at pH 6.6 or in the presence of added CoA) or malate dehydrogenase (at pH 7.9) were involved in this oxidation. At pH 7.9, the oxaloacetate produced progressively inhibited the succinate dehydrogenase. In the presence of ATP the production of oxaloacetate was stopped, and succinate dehydrogenase was protected from inhibition by oxaloacetate. However, previously accumulated oxaloacetate transitorily decreased the level of the reduction of the NAD+ driven by succinate, by causing the reversal of the malate dehydrogenase reaction. Under these conditions (i.e. presence of ATP), rotenone strongly inhibited the reduction of NAD+ by succinate-driven reverse electron flow. No evidence for an active reverse electron transport through a rotenone-insensitive path could be obtained. The inhibitory effect of rotenone was masked if malate had previously accumulated, owing to the malate-oxidizing enzymes which reduced part or all of the matrix NAD+.

scholarly journals Studies on the Energy Metabolism of Human Leukocytes

Blood ◽  
1967 ◽  
Vol 30 (2) ◽  
pp. 168-175 ◽  
Author(s):  
JOHN M. FOSTER ◽  
MARY L. TERRY ◽  
Harriet Gunther
Keyword(s):  
Energy Metabolism ◽  
Electron Transport ◽  
Oxidative Phosphorylation ◽  
Respiratory Control ◽  
Endogenous Respiration ◽  
Mitochondrial Oxidative Phosphorylation ◽  
Human Leukocytes ◽  
Endogenous Activity ◽  
Stimulation Of

Abstract 1. Oxidative phosphorylation has been studied in mitochondrial preparations from human leukocytes, using recently developed methods for homogenization, measuring respiration, and assaying for ATP. 2. Appreciable stimulation of both respiration and phosphorylation was limited to 3 substrates: succinate, malate, and α-glycerophosphate. The effects of other substrates were minimal. 3. The stimulating effects of these 3 substrates responded to inhibitors in a manner typical of mitochondrial oxidative phosphorylation. There was also considerable endogenous activity which, however, was insensitive to inhibitors. It is concluded the endogenous respiration and phosphorylation are not associated with electron transport. Subtracting their values from the data, P/O ratios consistent with good phosphorylation with the 3 substrates are obtained. 4. Studies with oligomycin and dinitrophenol suggest the presence of respiratory control. This indicates the mitochondria are intact. It is concluded that in the intact leukocyte the mitochondria are a major source of ATP.

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