scholarly journals A study on the tricarboxylic acid cycle and the synthesis of acetylcholine in the lobster nerve

1970 ◽  
Vol 118 (3) ◽  
pp. 451-455 ◽  
Author(s):  
S.-C. Cheng ◽  
R. Nakamura
Keyword(s):  
Tricarboxylic Acid Cycle ◽  
Relative Magnitude ◽  
Tricarboxylic Acid ◽  
Acetyl Coa ◽  
Acid Cycle ◽  
Cleavage Enzyme ◽  
Choline Acetylase ◽  
Probable Presence ◽  
Metabolic Compartments ◽  
Slow Turnover

1. The pattern of metabolism of 14C-labelled substrates in the lobster nerve suggested a normal tricarboxylic acid cycle with a slow turnover. 2. Acetylcholine was synthesized from [2-14C]acetate, [2-14C]pyruvate and [1,5-14C]citrate, implying the presence of acetate thiokinase, choline acetylase and citrate-cleavage enzyme. 3. [2-14C]Acetate was the best precursor. 4. The formation of acetyl-CoA from citrate was limited, probably by the citrate-cleavage enzyme, although the magnitude of the reversed reactions of the tricarboxylic acid cycle was large when compared with that of the forward reactions. 5. The relative magnitude of the two pathways (acetyl-CoA and carbon dioxide fixation) in pyruvate utilization was nearly equal. 6. The probable presence of metabolic compartments in the lobster nerve is discussed.

13C isotopomer model for estimation of anaplerotic substrate oxidation via acetyl-CoA

1996 ◽  
Vol 271 (4) ◽  
pp. E788-E799 ◽  
Author(s):  
F. M. Jeffrey ◽  
C. J. Storey ◽  
A. D. Sherry ◽  
C. R. Malloy
Keyword(s):  
Biochemical Analysis ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Acetyl Coa ◽  
Acid Cycle ◽  
Propionate Metabolism ◽  
13C Nuclear Magnetic Resonance ◽  
Isotopomer Analysis ◽  
Tricarboxylic Acid Cycle Intermediates ◽  
Anaplerotic Pathway

A previous model using 13C nuclear magnetic resonance isotopomer analysis provided for direct measurement of the oxidation of 13C-enriched substrates in the tricarboxylic acid cycle and/or their entry via anaplerotic pathways. This model did not allow for recycling of labeled metabolites from tricarboxylic acid cycle intermediates into the acetyl-CoA pool. An extension of this model is now presented that incorporates carbon flow from oxaloacetate or malate to acetyl-CoA. This model was examined using propionate metabolism in the heart, in which previous observations indicated that all of the propionate consumed was oxidized to CO2 and water. Application of the new isotopomer model shows that 2 mM [3-13C]propionate entered the tricarboxylic acid cycle as succinyl-CoA (an anaplerotic pathway) at a rate equal to 52% of tricarboxylic acid cycle turnover and that all of this carbon entered the acetyl-CoA pool and was oxidized. This was verified using standard biochemical analysis; from the rate (mumol.min-1.g dry wt-1) of propionate uptake (4.0 +/- 0.7), the estimated oxygen consumption (24.8 +/- 5) matched that experimentally determined (24.4 +/- 3).

Effect ofEchinococcus multilocularison the origin of acetyl-CoA entering the tricarboxylic acid cycle in host liver

2002 ◽  
Vol 76 (1) ◽  
pp. 31-36 ◽  
Author(s):  
C. Kepron ◽  
M. Novak ◽  
B.J. Blackburn
Keyword(s):  
Carbohydrate Metabolism ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Meriones Unguiculatus ◽  
Host Liver ◽  
Acetyl Coa ◽  
Acid Cycle ◽  
A Value ◽  
Alveolar Hydatid Disease ◽  
And Control

AbstractCarbon-13 nuclear magnetic resonance (NMR) spectroscopy was employed to investigate alterations in hepatic carbohydrate metabolism inMeriones unguiculatusinfected withEchinococcus multilocularis. Following portal vein injections of an equimolar mixture of ]#x005B;1,2-13C2]acetate and [3-13C]lactate, perchloric acid extracts of the livers were prepared and NMR spectra obtained. Isotopomer analysis using glutamate resonances in these spectra showed that the relative contributions of endogenous and exogenous substrates to the acetyl-CoA entering the tricarboxylic acid cycle differed significantly between infected and control groups. The mole fraction of acetyl-CoA that was derived from endogenous, unlabelled sources (FU) was 0.50±0.10 in controls compared to 0.34±0.04 in infected animals. However, the fraction of acetyl-CoA derived from [3-13C]lactate (FLL) was larger in livers of infected animals than those from controls with values of 0.27±0.04 and 0.18±0.04, respectively. Similarly, the fraction of acetyl-CoA derived from [1,2-13C2]acetate (FLA) was larger in livers of infected animals compared to those in controls; the fractions were 0.38±0.01 and 0.32±0.07, respectively. The ratio of FLA:FLLwas significantly smaller in the infected group with a value of 1.42±0.18 compared to 1.74±0.09 for the controls. These results indicate that alveolar hydatid disease has a pronounced effect on the partitioning of substrates within the pathways of carbohydrate metabolism in the host liver.

A general model for analysis of the tricarboxylic acid cycle with use of [13C]glutamate isotopomer measurements

1994 ◽  
Vol 266 (6) ◽  
pp. E1012-E1022 ◽  
Author(s):  
J. A. Vogt ◽  
A. J. Fischman ◽  
M. Kempf ◽  
Y. M. Yu ◽  
R. G. Tompkins ◽  
...  
Keyword(s):  
13C Nmr ◽  
Tricarboxylic Acid Cycle ◽  
Nonlinear Least Squares ◽  
Tricarboxylic Acid ◽  
Acetyl Coa ◽  
Metabolic System ◽  
Acid Cycle ◽  
Nmr Data ◽  
13C Nuclear Magnetic Resonance ◽  
Model Equations

A generalized steady-state model was developed for determining tricarboxylic acid cycle fractional fluxes from 13C nuclear magnetic resonance (NMR) data. The model relates the measured mole fractions of [13C]glutamate isotopomers to the fractional fluxes and predicted mole fractions of isotopomers of oxaloacetate (OAA) and acetyl-CoA. This model includes cycling between OAA and fumarate. Fractional fluxes are determined by fitting the model equations to NMR parameters by use of nonlinear least squares. Although only fractional fluxes can be determined from 13C-NMR data, when they are combined with mass spectroscopic measurements, absolute values can be derived. A specific metabolic system represented by published 13C-NMR data from extracts of hearts perfused with [13C]acetate, [13C]pyruvate (PYR), and [13C]acetate plus [13C]PYR was used to test the model. The intensities of predicted 13C-NMR splitting patterns were compared with observed values, and there was excellent agreement between observed and predicted signal intensities. With this model, important physiological parameters, including the OAA-derived fraction of inflow to PYR, PYR-derived fraction of inflow to acetyl-CoA, citrate-derived fraction of inflow to OAA, and PYR-derived fraction of inflow to OAA, can be determined.

Sources of acetyl-CoA entering the tricarboxylic acid cycle as determined by analysis of succinate carbon-13 isotopomers

Biochemistry ◽  
1993 ◽  
Vol 32 (45) ◽  
pp. 12240-12244 ◽  
Author(s):  
John G. Jones ◽  
A. Dean Sherry ◽  
F. Mark H. Jeffrey ◽  
Charles J. Storey ◽  
Craig R. Malloy
Keyword(s):  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Acetyl Coa ◽  
Acid Cycle

scholarly journals The activities of 2-oxoglutarate dehydrogenase and pyruvate dehydrogenase in hearts and mammary glands from ruminants and non-ruminants

1977 ◽  
Vol 164 (2) ◽  
pp. 349-355 ◽  
Author(s):  
G Read ◽  
B Crabtree ◽  
G H Smith
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Tricarboxylic Acid Cycle ◽  
Mammary Glands ◽  
Tricarboxylic Acid ◽  
Acetyl Coa ◽  
Simple Method ◽  
Acid Cycle ◽  
Maximum Flux ◽  
Oxoglutarate Dehydrogenase

1. The activities of 2-oxoglutarate dehydrogenase (EC 1.2.4.2) were measured in hearts and mammary glands of rats, mice, rabbits, guinea pigs, cows, sheep, goats and in the flight muscles of several Hymenoptera. 2. The activity of 2-oxoglutarate dehydrogenase was similar to the maximum flux through the tricarboxylic acid cycle in vivo. Therefore measuring the activity of this enzyme may provide a simple method for estimating the maximum flux through the cycle for comparative investigations. 3. The activities of pyruvate dehydrogenase (EC 1.2.4.1) in mammalian hearts were similar to those of 2-oxoglutarate dehydrogenase, suggesting that in these tissues the tricarboxylic acid cycle can be supplied (under some conditions) by acetyl-CoA derived from pyruvate alone. 4. In the lactating mammary glands of the rat and mouse, the activities of pyruvate dehydrogenase exceeded those of 2-oxoglutarate dehydrogenase, reflecting a flux of pyruvate to acetyl-CoA for fatty acid synthesis in addition to that of oxidation via the tricarboxylic acid cycle. In ruminant mammary glands the activities of pyruvate dehydrogenase were similar to those of 2-oxoglutarate dehydrogenase, reflecting the absence of a significant flux of pyruvate to fatty acids in these tissues.

scholarly journals Pyruvate Dehydrogenase and Tricarboxylic Acid Cycle Enzymes Are Sensitive Targets of Traumatic Brain Injury Induced Metabolic Derangement

2019 ◽  
Vol 20 (22) ◽  
pp. 5774 ◽  
Author(s):  
Giacomo Lazzarino ◽  
Angela Maria Amorini ◽  
Stefano Signoretti ◽  
Giuseppe Musumeci ◽  
Giuseppe Lazzarino ◽  
...  
Keyword(s):  
Traumatic Brain Injury ◽  
Brain Injury ◽  
Pyruvate Dehydrogenase ◽  
Coenzyme A ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Gene Expressions ◽  
Acetyl Coa ◽  
Metabolic Derangement ◽  
Acid Cycle

Using a closed-head impact acceleration model of mild or severe traumatic brain injury (mTBI or sTBI, respectively) in rats, we evaluated the effects of graded head impacts on the gene and protein expressions of pyruvate dehydrogenase (PDH), as well as major enzymes of mitochondrial tricarboxylic acid cycle (TCA). TBI was induced in anaesthetized rats by dropping 450 g from 1 (mTBI) or 2 m height (sTBI). After 6 h, 12 h, 24 h, 48 h, and 120 h gene expressions of enzymes and subunits of PDH. PDH kinases and phosphatases (PDK1-4 and PDP1-2, respectively), citrate synthase (CS), isocitrate dehydrogenase (IDH), oxoglutarate dehydrogenase (OGDH), succinate dehydrogenase (SDH), succinyl-CoA synthase (SUCLG), and malate dehydrogenase (MDH) were determined in whole brain extracts (n = 6 rats at each time for both TBI levels). In the same samples, the high performance liquid chromatographic (HPLC) determination of acetyl-coenzyme A (acetyl-CoA) and free coenzyme A (CoA-SH) was performed. Sham-operated animals (n = 6) were used as controls. After mTBI, the results indicated a general transient decrease, followed by significant increases, in PDH and TCA gene expressions. Conversely, permanent PDH and TCA downregulation occurred following sTBI. The inhibitory conditions of PDH (caused by PDP1-2 downregulations and PDK1-4 overexpression) and SDH appeared to operate only after sTBI. This produced almost no change in acetyl-CoA and free CoA-SH following mTBI and a remarkable depletion of both compounds after sTBI. These results again demonstrated temporary or steady mitochondrial malfunctioning, causing minimal or profound modifications to energy-related metabolites, following mTBI or sTBI, respectively. Additionally, PDH and SDH appeared to be highly sensitive to traumatic insults and are deeply involved in mitochondrial-related energy metabolism imbalance.

scholarly journals Indole-3-acetic acid regulates the central metabolic pathways in Escherichia coli

Microbiology ◽  
2006 ◽  
Vol 152 (8) ◽  
pp. 2421-2431 ◽  
Author(s):  
C. Bianco ◽  
E. Imperlini ◽  
R. Calogero ◽  
B. Senatore ◽  
P. Pucci ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Metabolic Pathways ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Mrna Levels ◽  
Glyoxylate Shunt ◽  
Acetyl Coa ◽  
Acid Cycle ◽  
E Coli ◽  
K 12

The physiological changes induced by indoleacetic acid (IAA) treatment were investigated in the totally sequenced Escherichia coli K-12 MG1655. DNA macroarrays were used to measure the mRNA levels for all the 4290 E. coli protein-coding genes; 50 genes (1.1 %) exhibited significantly different expression profiles. In particular, genes involved in the tricarboxylic acid cycle, the glyoxylate shunt and amino acid biosynthesis (leucine, isoleucine, valine and proline) were up-regulated, whereas the fermentative adhE gene was down-regulated. To confirm the indications obtained from the macroarray analysis the activity of 34 enzymes involved in central metabolism was measured; this showed an activation of the tricarboxylic acid cycle and the glyoxylate shunt. The malic enzyme, involved in the production of pyruvate, and pyruvate dehydrogenase, required for the channelling of pyruvate into acetyl-CoA, were also induced in IAA-treated cells. Moreover, it was shown that the enhanced production of acetyl-CoA and the decrease of NADH/NAD+ ratio are connected with the molecular process of the IAA response. The results demonstrate that IAA treatment is a stimulus capable of inducing changes in gene expression, enzyme activity and metabolite level involved in central metabolic pathways in E. coli.

Studies on the carbohydrate metabolism of sheep. VIII. Hypoglycaemia and hyperketonaemia in undernourished and fasted pregnant ewes

1959 ◽  
Vol 10 (1) ◽  
pp. 81 ◽  
Author(s):  
RL Reid ◽  
JP Hogan
Keyword(s):  
Fatty Acids ◽  
Blood Glucose ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Blood Levels ◽  
Acetyl Coa ◽  
Mean Values ◽  
Acid Cycle ◽  
Wide Range ◽  
Highly Correlated

Relationships between blood levels of glucose, ketone bodies, volatile fatty acids (V.F.X.), and citrate have been studied in ewes fed on a submaintenance diet of wheaten chaff during the last 5 weeks of pregnancy. Pre-feeding levels, changes during S hr after feeding, and changes during fasting were studied. Pre-feeding hypoglycaemia was consistently more severe and the post'-prandial increase in blood glucose was less in ewes carrying twins than in ewes carrying single lambs. Blood citrate consistently increased after feeding, the magnitude of the increase depending on the extent of the increase in blood glucose. Mean citrate levels after feeding were highly correlated with mean glucose levels, which suggested that blood citrate reflected the activity of the tricarboxylic acid cycle in tissues. Pre-feeding ketone levels tended to vary inversely as blood glucose when hyperlietonaemia was moderate (less than 20 mg per cent. ketones) hut the correlation disappeared v-hen hyperketonaemia was severe (20-53 mg per cent.). When glucose increased appreciably after feeding, ketones usually declined and V.F.A. levels were normal, but when the increase in glucose was small and levels remained below 30 mg per cent. after feeding, ketone levels often did not change and V.F.A. levels were high. Mean values for ketones over a period of 8 hr after feeding were highly correlated with mean values for V.F.A. over a wide range. This can be explained on the basis of present knowledge of the metabolism of the acetyl-coenzyme A (acetyl- Co4) derived from absorbed acetate and from oxidation of higher fatty acids; it is suggested that the oxidation of acetyl-CoA is impaired as a result of depression of tricarboxylic acid cycle activity. During fasting, blood ketones varied inversely with glucose, but very high ketone levels (above 30 mg per cent.) were probably not due simply to the hypoglycaemia. The hypothesis is advanced that an excess of circulating hydrocortisone further depressed acetyl-CoA metabolism. The apparent correlations between blood glucose and ketones would then be due largely to the fact that the magnitude of the adrenal response, at any particular time in these experiments, was a function of the severity of hypoglycaemia and of the period during which it was previously maintained.

Inhibition of CO2 fixation in group D streptococci

1969 ◽  
Vol 15 (1) ◽  
pp. 57-60 ◽  
Author(s):  
Victor F. Lachica ◽  
Paul A. Hartman
Keyword(s):  
Phosphoenolpyruvate Carboxylase ◽  
Pyruvate Carboxylase ◽  
Co2 Fixation ◽  
Tricarboxylic Acid Cycle ◽  
Inhibitory Effect ◽  
Tricarboxylic Acid ◽  
Acetyl Coa ◽  
Acid Cycle ◽  
Tricarboxylic Acid Cycle Intermediates ◽  
Group D

The stimulatory effect of acetyl-CoA and the inhibitory effect by L-aspartate and some intermediates of the tricarboxylic acid cycle in the assimilation of CO2 by crude extracts of group D streptococci suggest that the pyruvate carboxylase of Streptococcus faecium and the phosphoenolpyruvate carboxylase of S. bovis are allosteric enzymes. This implies that these enzymes are sites for the control of the amount of aspartate and of the tricarboxylic acid cycle intermediates synthesized.

scholarly journals The tricarboxylic acid cycle in Dictyostelium discoideum. Metabolite concentrations, oxygen uptake and 14c-labelled amino acid labelling patterns

1979 ◽  
Vol 184 (3) ◽  
pp. 581-588 ◽  
Author(s):  
P J Kelly ◽  
J K Kelleher ◽  
B E Wright
Keyword(s):  
Amino Acid ◽  
Oxygen Uptake ◽  
Dictyostelium Discoideum ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Acetyl Coa ◽  
Acid Cycle ◽  
Stage Of Development ◽  
Metabolite Concentrations

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.

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