The soluble citric acid cycle enzymes ofDrosophila melanogaster. II. Tissue and intracellular distribution of aconitase and NADP-dependent isocitrate dehydrogenase

1972 ◽  
Vol 7 (2) ◽  
pp. 163-175 ◽  
Author(s):  
David J. Fox ◽  
Marianne Conscience-Egli ◽  
Erika Abächerli
Keyword(s):  
Citric Acid ◽  
Isocitrate Dehydrogenase ◽  
Citric Acid Cycle ◽  
Intracellular Distribution ◽  
Acid Cycle ◽  
Citric Acid Cycle Enzymes

Citric acid cycle enzymes and nitrogenase in nodules of Pisum sativum

1977 ◽  
Vol 23 (9) ◽  
pp. 1197-1200 ◽  
Author(s):  
W. G. W. Kurz ◽  
T. A. LaRue
Keyword(s):  
Nitrogen Fixation ◽  
Citric Acid ◽  
Pisum Sativum ◽  
Isocitrate Dehydrogenase ◽  
Citric Acid Cycle ◽  
Acid Cycle ◽  
Isocitric Dehydrogenase ◽  
Citric Acid Cycle Enzymes

Activity of isocitric dehydrogenase (isocitrate dehydrogenase (NADP+); EC 1.1.1.42) in bacterids is highest at the time of maximum nitrogen fixation. It is likely that isocitric dehydrogenase is the source of reductant fordinitrogen fixation.

scholarly journals The activities of the citric acid-cycle enzymes in rat bone-marrow cells

1968 ◽  
Vol 108 (3) ◽  
pp. 413-415
Author(s):  
Eugene Goldwasser
Keyword(s):  
Bone Marrow ◽  
Citric Acid ◽  
Citric Acid Cycle ◽  
Citrate Synthase ◽  
Bone Marrow Cells ◽  
Mitochondrial Enzymes ◽  
Acid Cycle ◽  
Citric Acid Cycle Enzymes ◽  
Rat Bone ◽  
Marrow Cells

The activities of the eight citric acid-cycle enzymes of rat bone-marrow cells were determined along with several other mitochondrial and non-mitochondrial enzymes. Four of the citric acid-cycle enzymes (aconitase, succinyl-CoA thiokinase, α-oxoglutarate dehydrogenase and succinate dehydrogenase) have closely similar low activities; two [isocitrate dehydrogenase (NAD) and citrate synthase] have intermediate activities; the remaining two (malate dehydrogenase and fumarase) have high activities. The other enzymes surveyed also exhibited a spread of three orders of magnitude, the mitochondrial enzymes showing no less variation than the others.

scholarly journals Activities of citrate synthase and NAD+-linked and NADP+-linked isocitrate dehydrogenase in muscle from vertebrates and invertebrates

1976 ◽  
Vol 154 (3) ◽  
pp. 689-700 ◽  
Author(s):  
P R. Alp ◽  
E A. Newsholme ◽  
V A. Zammit
Keyword(s):  
Citric Acid ◽  
Isocitrate Dehydrogenase ◽  
Citric Acid Cycle ◽  
Citrate Synthase ◽  
Insect Flight ◽  
Mechanical Activity ◽  
Activity Data ◽  
Acid Cycle ◽  
Equilibrium Reaction ◽  
Flight Muscles

1. The activities of citrate synthase, NAD+-linked and NADP+-linked isocitrate dehydrogenase were measured in muscles from a large number of animals, in order to provide some indication of the importance of the citric acid cycle in these muscles. According to the differences in enzyme activities, the muscles can be divided into three classes. First, in a number of both vertebrate and invertebrate muscles, the activities of all three enzymes are very low. It is suggested that either the muscles use energy at a very low rate or they rely largely on anaerobic glycolysis for higher rates of energy formation. Second, most insect flight muscles contain high activities of citrate synthase and NAD+-linked isocitrate dehydrogenase, but the activities of the NADP+-linked enzyme are very low. The high activities indicate the dependence of insect flight on energy generated via the citric acid cycle. The flight muscles of the beetles investigated contain high activities of both isocitrate dehydrogenases. Third, other muscles of both vertebrates and invertebrates contain high activities of citrate synthase and NADP+-liniked isocitrate dehydrogenase. Many, if not all, of these muscles are capable of sustained periods of mechanical activity (e.g. heart muscle, pectoral muscles of some birds). Consequently, to support this activity fuel must be supplied continually to the muscle via the circulatory system which, in most animals, also transports oxygen so that energy can be generated by complete oxidation of the fuel. It is suggested that the low activities of NAD+-linked isocitrate dehydrogenase in these muscles may be involved in oxidation of isocitrate in the cycle when the muscles are at rest. 2. A comparison of the maximal activities of the enzymes with the maximal flux through the cycle suggests that, in insect flight muscle, NAD+-linked isocitrate dehydrogenase catalyses a non-equilibrium reaction and citrate synthease catalyses a near-equilibrium reaction. In other muscles, the enzyme-activity data suggest that both citrate synthase and the isocitrate dehydrogenase reactions are near-equilibrium.

The extraordinary mitochondrion and unusual citric acid cycle in Trypanosoma brucei

2005 ◽  
Vol 33 (5) ◽  
pp. 967-971 ◽  
Author(s):  
J.J. van Hellemond ◽  
F.R. Opperdoes ◽  
A.G.M. Tielens
Keyword(s):  
Citric Acid ◽  
Energy Metabolism ◽  
Trypanosoma Brucei ◽  
Citric Acid Cycle ◽  
Clinical Importance ◽  
African Trypanosomes ◽  
Acid Cycle ◽  
Fermentative Metabolism ◽  
Influence Of Substrate ◽  
Citric Acid Cycle Enzymes

African trypanosomes are parasitic protozoa that cause sleeping sickness and nagana. Trypanosomes are not only of scientific interest because of their clinical importance, but also because these protozoa contain several very unusual biological features, such as their specially adapted mitochondrion and the compartmentalization of glycolytic enzymes in glycosomes. The energy metabolism of Trypanosoma brucei differs significantly from that of their hosts and changes drastically during the life cycle. Despite the presence of all citric acid cycle enzymes in procyclic insect-stage T. brucei, citric acid cycle activity is not used for energy generation. Recent investigations on the influence of substrate availability on the type of energy metabolism showed that absence of glycolytic substrates did not induce a shift from a fermentative metabolism to complete oxidation of substrates. Apparently, insect-stage T. brucei use parts of the citric acid cycle for other purposes than for complete degradation of mitochondrial substrates. Parts of the cycle are suggested to be used for (i) transport of acetyl-CoA units from the mitochondrion to the cytosol for the biosynthesis of fatty acids, (ii) degradation of proline and glutamate to succinate, (iii) generation of malate, which can then be used for gluconeogenesis. Therefore the citric acid cycle in trypanosomes does not function as a cycle.

scholarly journals Lipotoxic Palmitate Impairs the Rate of β-Oxidation and Citric Acid Cycle Flux in Rat Neonatal Cardiomyocytes

2016 ◽  
Vol 40 (5) ◽  
pp. 969-981 ◽  
Author(s):  
Taha Haffar ◽  
Ali Akoumi ◽  
Nicolas Bousette
Keyword(s):  
Fatty Acid ◽  
Citric Acid ◽  
Dehydrogenase Activity ◽  
Fatty Acid Oxidation ◽  
Isocitrate Dehydrogenase ◽  
Lipid Accumulation ◽  
Citric Acid Cycle ◽  
Acid Oxidation ◽  
Acid Cycle ◽  
Neonatal Cardiomyocytes

Background/Aims: Diabetic hearts exhibit intracellular lipid accumulation. This suggests that the degree of fatty acid oxidation (FAO) in these hearts is insufficient to handle the elevated lipid uptake. We previously showed that palmitate impaired the rate of FAO in primary rat neonatal cardiomyocytes. Here we were interested in characterizing the site of FAO impairment induced by palmitate since it may shed light on the metabolic dysfunction that leads to lipid accumulation in diabetic hearts. Methods: We measured fatty acid oxidation, acetyl-CoA oxidation, and carnitine palmitoyl transferase (Cpt1b) activity. We measured both forward and reverse aconitase activity, as well as NAD+ dependent isocitrate dehydrogenase activity. We also measured reactive oxygen species using the 2', 7'-Dichlorofluorescin Diacetate (DCFDA) assay. Finally we used thin layer chromatography to assess diacylglycerol (DAG) levels. Results: We found that palmitate significantly impaired mitochondrial β-oxidation as well as citric acid cycle flux, but not Cpt1b activity. Palmitate negatively affected net aconitase activity and isocitrate dehydrogenase activity. The impaired enzyme activities were not due to oxidative stress but may be due to DAG mediated PKC activation. Conclusion: This work demonstrates that palmitate, a highly abundant fatty acid in human diets, causes impaired β-oxidation and citric acid cycle flux in primary neonatal cardiomyocytes. This metabolic defect occurs prior to cell death suggesting that it is a cause, rather than a consequence of palmitate mediated lipotoxicity. This impaired mitochondrial metabolism can have important implications for metabolic diseases such as diabetes and obesity.

Organization of citric acid cycle enzymes into a multienzyme cluster

FEBS Letters ◽  
1986 ◽  
Vol 201 (2) ◽  
pp. 267-270 ◽  
Author(s):  
Sarah J. Barnes ◽  
P.D.J. Weitzman
Keyword(s):  
Citric Acid ◽  
Citric Acid Cycle ◽  
Acid Cycle ◽  
Citric Acid Cycle Enzymes
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