A micromethod for the purification and quantification of organic acids of the tricarboxylic acid cycle in plant tissues.
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Chromatography, Gas↗
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Aliphatic medium chain tricarboxylic acids in rat urine.
Three aliphatic tricarboxylic acids have been found in rat urine. They have been identified as 6-carboxy-5-undecenedioic acid, 6-carboxy-5-dodecenedoic acid, and 6-carboxy-5-tridecenedioic acid. The carbon skeleton structure was determined by mass spectra of the hydrogenated methyl esters. The double bond position was determined after osmium tetroxide oxidation followed by trifluoroacetylation and mass spectrometry and by infrared spectrometry. The compounds were present in the urine when the rats were fed on pellets but disappeared when they received sucrose and water. The acids were not present in the pellets, and a metabolic relation to compounds of longer chain length, possibly mycolic acids, is likely.
Animals↗
Physiology and metabolism of pathogenic neisseria: tricarboxylic acid cycle activity in Neisseria gonorrhoeae.
Tricarboyxlic acid cycle activity was examined in Neisseria gonorrhoeae CS-7. The catabolism of glucose in N. gonorrheae by a combination of the Entner-Doudoroff and pentose phosphate pathways resulted in the accumulation of acetate, which was not further catabolized until the glucose was depleted or growth became limiting. Radiorespirometric studies revealed that the label in the 1 position of acetate was converted to CO2 at twice the rate of the label in the 2 position, indicating the presence of a tricarboxylic acid cycle. Growth on glucose markedly reduced the levels of all tricarboxylic acid cycle enzymes except citrate synthase (EC 4.1.3.7). Extracts of glucose-grown cells contained detectable levels of all tricarboxylic acid cycle enzymes except aconitase (EC 4.2.1.3), isocitrate dehydrogenase (EC 1.1.1.42), and a pyridine nucleotide-dependent malate dehydrogenase (EC 1.1.1.37). Extracts of cells capable of oxidizing acetate lacked only the pyridine nucleotide-dependent malate dehydrogenase. In lieu of this enzyem, a particulate pyridine nucleotide-independent malate oxidase (EC 1.1.3.3) was present. This enzyme required flavin adenine dinucleotide for activity and appeared to be associated with the electron transport chain. Radiorespirometric studies utilizing labeled glutamate demonstrated that a portion of the tricarboxylic acid cycle functioned during glucose catabolism. In spite of the presence of all tricarboxylic acid cycle enzymes, N. gonorrhoeae CS-7 was unable to grow in medium supplemented with cycle intermediates.
Acetates↗
Tricarboxylic acid cycle enzyme activities in adult Schistosoma mansoni and Schistosoma japonicum.
Reduced tricarboxylic acid cycle enzyme activities were found in paired adult Schistosoma mansoni and S. japonicum in comparison to those reported for S. mansoni cercariae (Coles, 1973). Succinate dehydrogenase activity, which has not been previously reported for either adult blood fluke, is more than twice as great in paired adult S. japonicum as in paired adult S. mansoni, but the activity is low in both species of adult worms. The similar low levels of tricarboxylic acid cycle enzyme activities which occur in adult S. mansoni and S. japonicum further substantiate the fact that anaerobic glycolysis is the major energy source in adults of both species.
Animals↗
[Characteristics of the tricarboxylic acid cycle in Nocardia erythropolis].
The activity of enzymes involved in the tricarboxylic acid cycle was studied in Nocardia erythropolis IBFM B-293. It was found to be low and hardly change, with some exceptions, in the course of growth in the presence of various carbon sources. Acetate induced enzymes of the glyoxylate cycle which was here an important mechanism of oxalacetate synthesis. The absence of alpha-ketoglutarate dehydrogenase in the case of all studied substrates and the absence of 4-aminobutyrate aminotransferase, the key enzyme of the compensating 4-aminobutyrate shunt, suggest that the tricarboxylic acid cycle is decoupled. Therefore, this cycle does not operate as a mechanism generating energy in N. erythropolis, but fulfills mainly biosynthetic functions.
Citric Acid Cycle↗
Glycolytic and tricarboxylic acid cycle enzyme activities during intraperiplasmic growth of Bdellovibrio bacteriovorus on Escherichia coli.
Selected enzyme activities were measured in extracts of the total cell pellets obtained at various times during aerobic intraperiplasmic growth of Bdellovibrio bacteriovorus 109J on anaerobically grown Escherichia coli substrate cells. Initially, the glycolytic enzyme activities were associated with the input of E. coli and the tricarboxylic acid cycle enzyme activities with the input of bdellovibrios. During the first 90 min of Bdellovibrio development, the glycolytic activities declined about 25 to 60%, whereas the tricarboxylic acid cycle activities increased about 10%. Between 110 and 180 min, the glycolytic activities decreased to trace levels and tricarboxylic acid cycle activities increased about 50 to 90%. Both bdellovibrio cell extracts and the cell-free growth menstruum (obtained after bdellovibrio growth on E. coli) caused the inactivation of glycolytic enzymes in E. coli extracts.
Bdellovibrio↗
Activity and androgenic control of enzymes associated with the tricarboxylic acid cycle, lipid oxidation and mitochondrial shuttles in the epididymis and epididymal spermatozoa of the rat.
1. Enzyme activities (units/g wet wt.) were determined in the caput and cauda epididymidis and in epididymal spermatozoa of the rat. 2. The activity of most enzymes in the cauda was between 50 and 100% of that in the caput, except that ATP citrate lyase was barely detectable in the cauda. 3. Spermatozoa, unlike epididymal tissue, contained sorbitol dehydrogenase but lacked ATP citrate lyase. NADP+-malate dehydrogenase, mitochondrial glycerol 3-phosphate dehydrogenase, succinate dehydrogenase, carnitine acetyltransferase and citrate synthase were 5 to 400 times as active in spermatozoa as in epididymal tissue. 4. 2-Oxoglutarate dehydrogenase was the least active member of the tricarboxylic acid cycle in all tissues and most closely matched the measured flux through the cycle. 5. The concentrations of hydroxyacyl-CoA dehydrogenase and carnitine palmitoyltransferase were equivalent to the more active enzymes of the tricarboxylic acid cycle, indicating the capacity for extensive lipid oxidation, and the presence of 3-hydroxybutyrate dehydrogenase suggests that these tissues can also oxidize ketone bodies. 6. Transfer of reducing equivalents from cytoplasm to mitochondrion is unlikely to occur by means of the glycerol phosphate cycle because mitochondrial glycerol 3-phosphate dehydrogenase is relatively inactive in epididymal tissue, whereas the cytoplasmic enzyme has little activity in spermatozoa, but transfer may be accomplished by the malate-aspartate shuttle. 7. Transfer of acetyl units from mitochondrion to cytoplasm could be effected by the pyruvate-malate cycle in the caput of androgen-maintained rats, but not in the other tissues because of the low activity of ATP citrate lyase. Acetyl unit transfer could take place via acetylcarnitine, mediated by carnitine acetyltransferase. 8. Castration resulted in a decrease in the concentration of nearly all enzymes, although subsequent administration of testosterone restored concentrations to values similar to those in animals maintained by endogenous androgen. The extent to which enzyme concentration was changed by an alteration in androgen status was highly variable, but was most marked in the case of pyruvate carboxylase.
Androgens↗
The tricarboxylic acid cycle in Dictyostelium discoideum. Metabolite concentrations, oxygen uptake and 14c-labelled amino acid labelling patterns.
Some aspects of tricarboxylic acid-cycle activity during differentiation and aging in Dictyostelium discoideum were examined. The concentrations of glutamate, aspartate, alanine, citrate, 2-oxoglutarate, succinate, fumarate, malate, oxaloacetate, pyruvate and acetyl-CoA were determined at four stages over the course of differentiation. The rate of O2 utilization was also determined over differentiation. In addition, experiments are described in which the specific radioactivities of citrate, 2-oxoglutarate, succinate, fumarate and malate were determined during a 30 min labelling of cells from the preculmination stage of development with [14C]glutamate, [14C]aspartate or [14C]alanine. A similar experiment was also performed with cells from the aggregation stage of development using [14C]glutamate.
Alanine↗
Tricarboxylic acid and glyoxylate cycles in the Leishmaniae.
Cell-free extacts of four species of Leishmania (L. brasiliensis, L. donovani, L. mexicana and L. tropica) have been shown to contain all enzymes of the tricarboxylic acid cycle. However, the activity of citrate synthase is so low that it is doubtful whether this pathway is of significance in the metabolism of carbohydrate substrates. All four species show the presence of the two enzymes (isocitrate lyase and malate synthase) characteristic of the glyoxylate bypass and glyoxylate is present in cell-free preparations. The isocitrate lyase is relatively insensitive to phosphoenolpyruvate (PEP). The glyoxylate cycle in the Leishmaniae, thus, seems to be independent of control by C3 compounds.
Citrate (si)-Synthase↗
Studies on the energetic metabolism of Shigella flexneri x Escherichia coli hybrids devoid of penetration ability. IV. Growth characteristics in the presence of some tricarboxylic acid cycle intermediates.
The dynamics of avirulant lac+KCP- hybrids Sh. flexneri multiplication was investigated in minimal medium in the presence of some tricarboxylic acid cycle intermediates (fumarate, succinate, malate) and pyruvate. It was established that in spite of the loss of virulence in the rate of the multiplication of the hybrid strains, in comparison with that of the virulent recipient strains of Sh. flexneri, considerable differences were not observed.
Cell Division↗
On the metabolic characteristics of hybrids Shigella flexneri x Escherichia coli, devoid of their ability for intracellular multiplication in the epithelial cells. IV. Growth characteristics in the presence of some tricarboxylic acid cycle intermediates.
The dynamics of avirulent xyl-str and xyl + hybrids Sh. flexneri was investigated in minimal medium in the presence of some tricarboxylic acid cycle intermediates (succinate, malate, fumarate) and pyruvate. It was established that the hybrids with a replaced xyl-str or xyl-region show a considerably lower rate of multiplication in artificial media than the virulent recipient strains.
Cell Division↗
Effect of Zinc on tricarboxylic acid cycle intermediates and enzymes in relation to aflatoxin biosynthesis.
The stimulatory action of zinc on aflatoxin production by Aspergillus parasiticus NRRL3240 has been investigated by studying the levels of tricarboxylic acid (TCA) cycle intermediates and related enzymes in the fungal mycelium. During the stationary phase of growth, the levels of alpha-keto acids declined in zinc-sufficient cultures compared with those in zinc-dificient cultures. TCA cycle enzymes did not show any significant changes due to zinc availability. In zinc-deficient cultures, enzymes of the TCA cycle had maximum activity on the fourth day, after which their activity declined. In zinc-sufficient cultures, some enzymes showed maximum activity on the fourth day, others on the second day.
Aflatoxins↗
Regulation of the tricarboxylic acid cycle and poly-beta-hydroxybutyrate metabolism in Azotobacter beijerinckii grown under nitrogen or oxygen limitation.
Azotobacter beijerinckii was grown in ammonia-free glucose/mineral salts media in chemostat culture under oxygen or nitrogen limitation. Selected enzymes of the tricarboxylic acid cycle and poly-beta-hydroxybutyrate metabolism were monitored in relation to oxygen supply for both steady and transition states. Two dissolved oxygen concentrations were used for the nitrogen-limited steady state to investigate the possible effects of respiratory protection of nitrogenase on these enzymes. The levels of NADH oxidase, isocitrate dehydrogenase and 2-oxoglutarate dehydrogenase increased markedly on relaxation of oxygen limitation while pyruvate dehydrogenase and citrate synthase were relatively unaffected. beta-Ketothiolase and acetoacetyl-CoA reductase levels decreased as oxygen limitation was relaxed. Respiratory activity, as measured by the QO2 value, increased with oxygen supply rate. Imposition of oxygen limitation on a nitrogen-limited culture caused an immediate increase in the NADH/NAD ratio but this rapidly readjusted to its previous steady-state value. These changes are discussed in relation to respiratory protection of nitrogenase and poly-beta-hydroxybutyrate metabolism in A. beijerinckii.
Acetyl-CoA C-Acetyltransferase↗
[Effect of carbonic acid of different concentrations of the glycolysis processes and tricarboxylic acid cycle in rat liver tissues].
A rise in the carbonic acid and pH level in rat blood determines an increase in oxidative properties of the liver cell cytoplasm. Simultaneously the content of alpha-ketoglutarate, isocitrate, glutamate, alpha-glycerophosphate, dihydroxyacetone phosphate, pyruvate, lactate, malate increases and the level of glucose, glutamine and ammonia decreases. The in vitro experiments showed that the rise in the level of carbonic acid in the incubation medium from 10 up to 40 mM under all the studied values of pH (7.2, 7.4, 7.6) stimulates formation of dihydroxyacetone phosphate, malate, pyruvate, alpha-ketoglutarate (by 1.5-2.0 times). The same regularity is observed for lactate and glutamate at pH 7.4 and 7.6. The increase in the level of carbonic acid under the all studied values of pH produces a 1.5-fold decrease in the ammonia concentration.
Animals↗
Transport of tricarboxylic acid cycle intermediates by membrane vesicles from renal brush border.
The uptake of citrate and alpha-ketoglutarate by membrane vesicles from rabbit renal brush border was studied by a rapid filtration technique. Both compounds exhibited transport characteristics similar to those seen for the sodium-dependent cotransport systems previously described for sugars and amino acids in brush border membranes. The estimated sodium-dependent Vmax and Km were 17 nmol per mg of protein per min and 0.18 mM for citrate and 17 nmol per mg of protein per min and 1.0 mM for alpha-ketoglutarate. The initial rate of citrate transport was 5 times that of sugars and amino acids under comparable conditions. Uptake rates of 0.1 mM citrate and alpha-ketoglutarate were inhibited by greater than 90% by 10 mM succinate, malate, fumarate, or oxaloacetate, indicating the presence in the brush border membrane of a transport system highly specialized for the renal conservation of intermediates of the tricarboxylic acid cycle.
Animals↗
[Occurrence of alpha-alkyl-substituted malic acids, and beta-hydroxy-beta-alkyl-substituted dicarboxylic and tricarboxylic acid derivatives in normal urine (author's transl)].
Urine contains a number of alpha-hydroxy acids so far unknown to occur in biological liquids. Besides the already as urine constituent known methylmalic acid, also the ethyl, isopropyl and butyl derivatives of malic acid were found. Further metabolites in urine are a beta-propyl-substituted beta-hydrosyglutaric acid, a beta-hydroxy-beta-[methyl-carbomethoxy]-adipinic acid and two isomeric alpha-methylcitric acids.
Esters↗
The tricarboxylic acid cycle in Dictyostelium discoideum. A model of the cycle at preculmination and aggregation.
A preliminary model of tricarboxylic acid-cycle activity in Dictyostelium discoideum is presented. Specific-radioactivity labelling patterns of intra- and extra-mitochondrial pools are simulated by this model and compared with the experimental data. The model arrived at by this method shows the following features. (1) The cycle flux rate is approx. 0.4 mM/min. (2) Both fumarate and malate are compartmentalized at approx. 1:5 between cycle pools and non-cycle pools. These may represent mitochondrial and cytoplasmic pools. Citrate is compartmentalized at 1:10. Succinate appears to exist in three compartments, two of which become labelled by [14C]glutamate and only one by [14C]aspartate (3) Two pools of aspartate with two associated pools of oxaloacetate are necessary for simulation. (4) Exchange between the cycle and non-cycle pools of both citrate and fumarate occurs at very low rates of about 0.003 mM/min, whereas exchange between the malate pools is about 0.004 mM/min. The exchange reaction glutamate in equilibrium 2-oxoglutarate runs at approx. 15 times the cycle flux. (5) A reaction catalysed by "malic" enzyme is included in the model, as this reaction is necessary for complete oxidation of amino acid substrates. (6) Calculation of the ATP yield from the model is consistent with earlier estimates of ATP turnover if the activity of adenylate kinase is considered.
Adenosine Triphosphate↗
Lytic effect of di- or tricarboxylic acids plus sodium dodecyl sulfate against Pseudomonas aeruginosa.
Pseudomonas aeruginosa was rapidly lysed and killed when treated with several multiple-carboxylic acids at 100 micrograms/ml, followed by exposure to sodium dodecyl sulfate at 5 mg/ml.
Azides↗