Citric-Acid Cycle Key Enzyme Activities during In vitro Growth and Metacyclogenesis of Leishmania infantum Promastigotes

1999 ◽  
Vol 85 (4) ◽  
pp. 595 ◽  
Author(s):  
M. Louassini ◽  
M. Foulquie ◽  
R. Benitez ◽  
J. Adroher
Keyword(s):  
Citric Acid ◽  
Enzyme Activities ◽  
Leishmania Infantum ◽  
Citric Acid Cycle ◽  
In Vitro Growth ◽  
Acid Cycle ◽  
Key Enzyme

Enzymes of Glucose Metabolism in the Caecum of the Marine Borer Bankia setacea

1970 ◽  
Vol 27 (6) ◽  
pp. 1141-1146 ◽  
Author(s):  
D. L. Liu ◽  
C. C. Walden
Keyword(s):  
Citric Acid ◽  
Glucose Metabolism ◽  
Enzyme Activities ◽  
Citric Acid Cycle ◽  
Acid Cycle ◽  
Modified Embden Meyerhof Pathway

The caecum of the marine borer Bankia setacea was found to contain the enzymes for a modified Embden–Meyerhof pathway, a pentose cycle, and a complete citric acid cycle. The pathways are linked to the digestion of cellulose by the enzyme cellobiase. Significant numbers of bacteria were not detected in the caecum of the borer. Enzyme activities in the citric acid cycle indicate a biosynthesis role for the caecum.

Studies on the Citric Acid Cycle and its Portion of Glucose Breakdown by Calf and Bovine Lenses in vitro

1971 ◽  
Vol 2 (3-4) ◽  
pp. 143-148 ◽  
Author(s):  
O. Hockwin ◽  
G. Blum ◽  
I. Korte ◽  
T. Murata ◽  
W. Radetzki ◽  
...  
Keyword(s):  
Citric Acid ◽  
Citric Acid Cycle ◽  
Acid Cycle

scholarly journals Production of tricarballylic acid by rumen microorganisms and its potential toxicity in ruminant tissue metabolism

1986 ◽  
Vol 56 (1) ◽  
pp. 153-162 ◽  
Author(s):  
James B. Russell ◽  
Neil Forsberg
Keyword(s):  
Citric Acid ◽  
Citric Acid Cycle ◽  
Competitive Inhibitor ◽  
Rumen Microorganisms ◽  
Aconitate Hydratase ◽  
Factors Affecting ◽  
Acid Cycle ◽  
Rat Liver Cells ◽  
High Concentrations

1. Rumen microorganisms convert trans-aconitate to tricarballylate. The following experiments describe factors affecting the yield of tricarballylate, its absorption from the rumen into blood and its effect on mammalian citric acid cycle activity in vitro.2. When mixed rumen microorganisms were incubated in vitro with Timothy hay (Phleum praiense L.) and 6.7 mM-trans-aconitate, 64 % of the trans-aconitate was converted to tricarballylate. Chloroform and nirate treatments inhibited methane production and increased the yield of tricarballylate to 82 and 75% respectively.3. Sheep given gelatin capsules filled with 20 g trans-aconitate absorbed tricarballylate and the plasma concentration ranged from 0.3 to 0.5 mM 9 h after administration. Feeding an additional 40 g potassium chloride had little effect on plasma tricarballylate concentrations. Between 9 and 36 h there was a nearly linear decline in plasma tricarballylate.4. Tricarballylate was a competitive inhibitor of the enzyme, aconitate hydratase (aconitase; EC 4.2.1.3), and the inhibitor constant, KI, was 0.52 mM. This KIvalue was similar to the Michaelis-Menten constant (Km) of the enzyme for citrate.5. When liver slices from sheep were incubated with increasing concentrations of tricarballylate, [I4C]acetate oxidation decreased. However, even at relatively high concentrations (8 mM), oxidation was still greater than 80% of the maximum. Oxidation of [I4C]acetate by isolated rat liver cells was inhibited to a greater extent by tricarballylate. Concentrations as low as 0.5 mM caused a 30% inhibition of citric acid cycle activity.

scholarly journals Inhibition of Hypoxia-inducible Factor (HIF) Hydroxylases by Citric Acid Cycle Intermediates

2006 ◽  
Vol 282 (7) ◽  
pp. 4524-4532 ◽  
Author(s):  
Peppi Koivunen ◽  
Maija Hirsilä ◽  
Anne M. Remes ◽  
Ilmo E. Hassinen ◽  
Kari I. Kivirikko ◽  
...  
Keyword(s):  
Citric Acid ◽  
Transcriptional Activity ◽  
Citric Acid Cycle ◽  
Dimethyl Ester ◽  
Hypoxia Inducible Factor ◽  
Fumarate Hydratase ◽  
High Concentration ◽  
Cultured Fibroblasts ◽  
Acid Cycle

The stability and transcriptional activity of the hypoxia-inducible factors (HIFs) are regulated by two oxygen-dependent events that are catalyzed by three HIF prolyl 4-hydroxylases (HIF-P4Hs) and one HIF asparaginyl hydroxylase (FIH). We have studied possible links between metabolic pathways and HIF hydroxylases by analyzing the abilities of citric acid cycle intermediates to inhibit purified human HIF-P4Hs and FIH. Fumarate and succinate were identified as in vitro inhibitors of all three HIF-P4Hs, fumarate having Ki values of 50–80 μm and succinate 350–460 μm, whereas neither inhibited FIH. Oxaloacetate was an additional inhibitor of all three HIF-P4Hs with Ki values of 400–1000 μm and citrate of HIF-P4H-3, citrate being the most effective inhibitor of FIH with a Ki of 110 μm. Culturing of cells with fumarate diethyl or dimethyl ester, or a high concentration of monoethyl ester, stabilized HIF-1α and increased production of vascular endothelial growth factor and erythropoietin. Similar, although much smaller, changes were found in cultured fibroblasts from a patient with fumarate hydratase (FH) deficiency and upon silencing FH using small interfering RNA. No such effects were seen upon culturing of cells with succinate diethyl or dimethyl ester. As FIH was not inhibited by fumarate, our data indicate that the transcriptional activity of HIF is quite high even when binding of the coactivator p300 is prevented. Our data also support recent suggestions that the increased fumarate and succinate levels present in the FH and succinate dehydrogenase-deficient tumors, respectively, can inhibit the HIF-P4Hs with consequent stabilization of HIF-αs and effects on tumor pathology.

ZUR LOKALISATION DER INNERSEKRETORISCHEN FUNKTION DES MENSCHLICHEN OVARS

1964 ◽  
Vol 46 (4) ◽  
pp. 580-596 ◽  
Author(s):  
Hartmut Brandau ◽  
Wilfried Luh
Keyword(s):  
Citric Acid ◽  
Enzyme Activities ◽  
Citric Acid Cycle ◽  
Glycolytic Enzymes ◽  
Homogeneous Distribution ◽  
Hormone Production ◽  
Acid Cycle ◽  
Normal Human ◽  
Human Ovaries ◽  
Theca Interna

ABSTRACT The histochemical localization of some oxydative enzymes which catalize steps in the Embden-Meyerhof chain, hexosemonophosphate shunt and the citric acid cycle, was studied in normal human ovaries. In contrast to the very low concentration and homogeneous distribution of enzyme activities of the citric acid cycle in the ovarian components, the theca interna of the developing follicle and the theca and granulosa lutein cells show extremely high levels of activities of TPN-specific and glycolytic enzymes. Attempts were made to establish some relation between the findings mentioned above and the localization of hormone production. It was concluded that the synthesis of progesterone is located in the granulosa lutein cells while the formation of oestrogens takes place in the remaining ovarian components, which show a high activity of TPN-specific and glycolytic enzymes.

Differential effects of heptanoate and hexanoate on myocardial citric acid cycle intermediates following ischemia-reperfusion

2006 ◽  
Vol 100 (1) ◽  
pp. 76-82 ◽  
Author(s):  
Isidore C. Okere ◽  
Tracy A. McElfresh ◽  
Daniel Z. Brunengraber ◽  
Wenjun Martini ◽  
Joseph P. Sterk ◽  
...  
Keyword(s):  
Citric Acid ◽  
Citric Acid Cycle ◽  
Contractile Function ◽  
Ischemia Reperfusion ◽  
Negative Control ◽  
Saline Control ◽  
Acid Cycle ◽  
Treatment Groups ◽  
Reversible Ischemia

In the normal heart, there is loss of citric acid cycle (CAC) intermediates that is matched by the entry of intermediates from outside the cycle, a process termed anaplerosis. Previous in vitro studies suggest that supplementation with anaplerotic substrates improves cardiac function during myocardial ischemia and/or reperfusion. The present investigation assessed whether treatment with the anaplerotic medium-chain fatty acid heptanoate improves contractile function during ischemia and reperfusion. The left anterior descending coronary artery of anesthetized pigs was subjected to 60 min of 60% flow reduction and 30 min of reperfusion. Three treatment groups were studied: saline control, heptanoate (0.4 mM), or hexanoate as a negative control (0.4 mM). Treatment was initiated after 30 min of ischemia and continued through reperfusion. Myocardial CAC intermediate content was not affected by ischemia-reperfusion; however, treatment with heptanoate resulted in a more than twofold increase in fumarate and malate, with no change in citrate and succinate, while treatment with hexanoate did not increase fumarate or malate but increased succinate by 1.8-fold. There were no differences among groups in lactate exchange, glucose oxidation, oxygen consumption, and contractile power. In conclusion, despite a significant increase in the content of carbon-4 CAC intermediates, treatment with heptanoate did not result in improved mechanical function of the heart in this model of reversible ischemia-reperfusion. This suggests that reduced anaplerosis and CAC dysfunction do not play a major role in contractile and metabolic derangements observed with a 60% decrease in coronary flow followed by reperfusion.

ENZYMOLOGISCHE STUDIEN AM ARRHENOBLASTOM

1971 ◽  
Vol 67 (3) ◽  
pp. 577-589 ◽  
Author(s):  
H. Brandau ◽  
L. Brandau
Keyword(s):  
Enzyme Activity ◽  
Citric Acid ◽  
Enzyme Activities ◽  
Citric Acid Cycle ◽  
Hydroxysteroid Dehydrogenase ◽  
Pentose Phosphate ◽  
Testosterone Metabolism ◽  
Acid Cycle ◽  
Enzyme Activity Pattern ◽  
Pentose Phosphate Shunt

ABSTRACT In an arrhenoblastoma of a 24 years old female patient the enzyme activities of the intermediary carbonhydrate metabolism, the citric acid cycle, the glycerophosphate cycle, the pentose-phosphate shunt as well as the steroid-dehydrogenases were measured quantitatively and localized histochemically. The striking high activities of the glycolytic enzymes, the presence of steroid-dehydrogenases and the only moderately increased enzyme activities of the citric acid cycle in comparison with the stroma ovarii identify the arrhenoblastoma as a tissue with steroid hormonal metabolism. High activities of the mentioned enzymes and especially the activities of the steroid-dehydrogenases were localized histochemically only in Leydig-cell-like cells. Therefore these cells may be considered as structures of steroid-biogenesis. The enzyme activity pattern of the steroiddehydrogenases illuminates the biogenetic pathways of androgens. The low activities of the 17β-hydroxysteroid-dehydrogenase in this tissue in comparison with other steroid producing tissues indicate a special testosterone metabolism.

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