scholarly journals The tricarboxylic acid cycle in Dictyostelium discoideum. III. Analysis of steady state and dynamic behavior

1992 ◽  
Vol 267 (32) ◽  
pp. 22926-22933 ◽  
Author(s):  
F Shiraishi ◽  
M.A. Savageau
Keyword(s):  
Steady State ◽  
Dynamic Behavior ◽  
Dictyostelium Discoideum ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Acid Cycle

scholarly journals The redistribution of carbon label by the reactions involved in glycolysis, gluconeogenesis and the tricarboxylic acid cycle in rat liver

1968 ◽  
Vol 110 (2) ◽  
pp. 313-335 ◽  
Author(s):  
D. F. Heath
Keyword(s):  
Carbon Dioxide ◽  
Steady State ◽  
Rat Liver ◽  
Tricarboxylic Acid Cycle ◽  
Specific Radioactivity ◽  
Tricarboxylic Acid ◽  
State Theory ◽  
Variable Rate ◽  
Acid Cycle ◽  
Constant Rate

A scheme is presented that shows how the reactions involved in gluconeogenesis, glycolysis and the tricarboxylic acid cycle are linked in rat liver. Equations are developed that show how label is redistributed in aspartate, glutamate and phosphopyruvate when it is introduced as specifically labelled pyruvate or glucose either at a constant rate (steady-state theory) or at a variable rate (non-steady-state theory). For steady-state theory the fractions of label introduced as specifically labelled pyruvate that are incorporated into glucose and carbon dioxide are also given, and for both theories the specific radioactivities of aspartate and glutamate relative to the specific radioactivity of the substrate. The theories allow for entry of label into the tricarboxylic acid cycle via both oxaloacetate and acetyl-CoA, for 14CO2 fixation and for loss of label from the tricarboxylic acid cycle in glutamate, but not for losses in citrate. They also allow for incomplete symmetrization of label in oxaloacetate due to incomplete equilibration with fumarate both in the extramitochondrial part of the cell and in the mitochondrion on entry of oxaloacetate into the tricarboxylic acid cycle. In the latter case failure both of oxaloacetate to equilibrate with malate and of malate to equilibrate with fumarate are considered.

Intermediary carbohydrate metabolism in protoscoleces ofEchinococcus granulosus(horse and sheep strains) andE. multilocularis

Parasitology ◽  
1982 ◽  
Vol 84 (2) ◽  
pp. 351-366 ◽  
Author(s):  
D. P. McManus ◽  
J. D. Smyth
Keyword(s):  
Steady State ◽  
Carbohydrate Metabolism ◽  
Pyruvate Kinase ◽  
Energy Production ◽  
Alternative Energy ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Acid Cycle ◽  
State Content

SUMMARYWith few exceptions, the specific activities of the glycolytic enzymes and the steady-state content of glycolytic and associated intermediates in protoscoleces of the horse (E.g.H) and sheep (E.g.S) strains ofEchinococcus granulosusand the closely relatedE. multilocularis(E.m.) are very similar. Phosphorylase, hexokinase, phosphofructokinase and pyruvate kinase catalyse non-equilibrium reactions and the patterns of activity for pyruvate kinase, phosphoenolpyruvate carboxykinase and malic enzyme are similar in the three organisms. The levels of tricarboxylic acid cycle intermediates inE.g.H., E.g.S. andE.m. are of the same order as those reported in tissues with an active cycle. Each has a complete sequence of cycle enzymes but there are substantial differences between the three parasites with regard to the activity of individual enzymes, The activities of NAD and NADP-linked isocitrate dehydrogenases are significantly lower inE.g.H. than inE.g.S. and particularly inE.m. which suggests that the tricarboxylic acid cycle may play a more important role in carbohydrate metabolism and energy production in the latter parasites. Nevertheless, the three organisms utilize fermentative pathways for alternative energy production, fix carbon dioxide via phosphoenolpyruvate carboxykinase and have a partial reversed tricarboxylic acid cycle. It is speculated thatin vivomore carbon will be channelled towards oxaloacetate than pyruvate at the phosphoenolpyruvate branch point. The steady state content of ATP and the ATP/AMP ratios are low in the three organisms, suggesting a low rate of ATP utilization in each.

scholarly journals The tricarboxylic acid cycle in Dictyostelium discoideum. A model of the cycle at preculmination and aggregation

1979 ◽  
Vol 184 (3) ◽  
pp. 589-597 ◽  
Author(s):  
P J Kelly ◽  
J K Kelleher ◽  
B E Wright
Keyword(s):  
Dictyostelium Discoideum ◽  
Adenylate Kinase ◽  
Malic Enzyme ◽  
Tricarboxylic Acid Cycle ◽  
Specific Radioactivity ◽  
Tricarboxylic Acid ◽  
Complete Oxidation ◽  
Flux Rate ◽  
Acid Cycle ◽  
Preliminary Model

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.

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.

scholarly journals Analysis of tricarboxylic acid-cycle metabolism of hepatoma cells by comparison of 14CO2 ratios

1987 ◽  
Vol 246 (3) ◽  
pp. 633-639 ◽  
Author(s):  
J K Kelleher ◽  
B M Bryan ◽  
R T Mallet ◽  
A L Holleran ◽  
A N Murphy ◽  
...  
Keyword(s):  
Steady State ◽  
Tricarboxylic Acid Cycle ◽  
Tca Cycle ◽  
Tricarboxylic Acid ◽  
Hepatoma Cells ◽  
Acid Cycle ◽  
The Tca Cycle ◽  
14Co2 Production ◽  
Metabolic Properties ◽  
Tca Cycle Intermediates

The CO2-ratios method is applied to the analysis of abnormalities of TCA (tricarboxylic acid)-cycle metabolism in AS-30D rat ascites-hepatoma cells. This method utilizes steady-state 14CO2-production rates from pairs of tracers of the same compound to evaluate TCA-cycle flux patterns. Equations are presented that quantitatively convert CO2 ratios into estimates of probability of flux through TCA-cycle-related pathways. Results of this study indicated that the ratio of 14CO2 produced from [1,4-14C]succinate to 14CO2 produced from [2,3-14C]succinate was increased by the addition of glutamine (5 mM) to the medium. An increase in the succinate CO2 ratio is quantitatively related to an increased flux of unlabelled carbon into the TCA-cycle-intermediate pools. Analysis of 14C distribution in [14C]citrate derived from [2,3-14C]succinate indicated that flux from the TCA cycle to the acetyl-CoA-derived carbons of citrate was insignificant. Thus the increased succinate CO2 ratio observed in the presence of glutamine could only result from an increased flux of carbon into the span of the TCA cycle from citrate to oxaloacetate. This result is consistent with increased flux of glutamine to alpha-oxoglutarate in the incubation medium containing exogenous glutamine. Comparison of the pyruvate CO2 ratio, steady-state 14CO2 production from [2-14C]pyruvate versus [3-14C]pyruvate, with the succinate 14CO2 ratio detected flux of pyruvate to C4 TCA-cycle intermediates in the medium containing glutamine. This result was consistent with the observation that [14C]aspartate derived from [2-14C]pyruvate was labelled in C-2 and C-3. 14C analysis also produced evidence for flux of TCA-cycle carbon to alanine. This study demonstrates that the CO2-ratios method is applicable in the analysis of the metabolic properties of AS-30D cells. This methodology has verified that the atypical TCA-cycle metabolism previously described for AS-30D-cell mitochondria occurs in intact AS-30D rat hepatoma cells.

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