scholarly journals Role of pyruvate carboxylation in the energy-linked regulation of pool sizes of tricarboxylic acid-cycle intermediates in the myocardium

1982 ◽  
Vol 208 (3) ◽  
pp. 577-581 ◽  
Author(s):  
K J Peuhkurinen ◽  
E M Nuutinen ◽  
E P Pietiläinen ◽  
J K Hiltunen ◽  
I E Hassinen
Keyword(s):  
Tricarboxylic Acid Cycle ◽  
Specific Radioactivity ◽  
Tricarboxylic Acid ◽  
Acid Cycle ◽  
Metabolite Pool ◽  
Label Incorporation ◽  
Tricarboxylic Acid Cycle Intermediates ◽  
Pool Sizes

The increase in the metabolite pool size of the tricarboxylic acid cycle in the isolated perfused rat heart after a decrease in the ATP consumption by KCl-induced arrest was used to study the anaplerotic mechanisms. During net anaplerosis the label incorporation into the tricarboxylic acid-cycle intermediates from [1-14C]pyruvate increased and occurred mainly by pathways not involving prior release of the label to CO2. A method for determination of the specific radioactivity of mitochondrial pyruvate was devised, and the results corroborated the notion that tissue alanine can be used as an indicator of the specific radioactivity of intracellular pyruvate.

scholarly journals Elimination and replenishment of tricarboxylic acid-cycle intermediates in myocardium

1981 ◽  
Vol 194 (3) ◽  
pp. 867-875 ◽  
Author(s):  
E M Nuutinen ◽  
K J Peuhkurinen ◽  
E P Pietiläinen ◽  
J K Hiltunen ◽  
I E Hassinen
Keyword(s):  
Co2 Fixation ◽  
Tricarboxylic Acid Cycle ◽  
Linear Optimization ◽  
Tricarboxylic Acid ◽  
Acid Cycle ◽  
Rat Hearts ◽  
Label Incorporation ◽  
Perfused Rat Hearts ◽  
Tricarboxylic Acid Cycle Intermediates ◽  
Isolated Perfused Rat Hearts

1. The contribution of Co2 fixation to the anaplerotic mechanisms in the myocardium was investigated in isolated perfused rat hearts. 2. K+-induced arrest of the heart was used to elicit a transition in the concentrations of the intermediates of the tricarboxylic acid cycle. 3. Incorporation of 14C from [14]bicarbonate into tricarboxylic acid-cycle intermediates was measured and the rates of the reactions of the cycle were estimated by means of a linear optimization program which solves the differential equations describing a simulation model of the tricarboxylic acid cycle and related reactions. 4. The results showed that the rate of CO2 fixation is dependent on the metabolic state of the myocardium. Upon a sudden diminution of cellular ATP consumption, the pool size of the tricarboxylic acid-cycle metabolites increased and the rate of label incorporation from [14C]bicarbonate into the cycle metabolites increased simultaneously. The computer model was necessary to separate the rapid equilibration between bicarbonate and some metabolites from the potentially anaplerotic reactions. The main route of anaplerosis during metabolite accumulation was through malate + oxaloacetate. Under steady-state conditions there was a constant net outward flow from the tricarboxylic acid cycle via the malate + oxaloacetate pool, with a concomitant anaplerotic flow from metabolites forming succinyl-CoA (3-carboxypropionyl-CoA).

scholarly journals Pyruvate carboxylation as an anaplerotic mechanism in the isolated perfused rat heart

1982 ◽  
Vol 202 (1) ◽  
pp. 67-76 ◽  
Author(s):  
K J Peuhkurinen ◽  
I E Hassinen
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Isocitrate Dehydrogenase ◽  
Tricarboxylic Acid Cycle ◽  
Specific Radioactivity ◽  
Tricarboxylic Acid ◽  
Acetate Metabolism ◽  
Acid Cycle ◽  
Pyruvate Carboxylation ◽  
Dehydrogenase Reaction ◽  
Tricarboxylic Acid Cycle Intermediates

1. The role of pyruvate carboxylation in the net synthesis of tricarboxylic acid-cycle intermediates during acetate metabolism was studied in isolated rat hearts perfused with [1-14C]pyruvate. 2. The incorporation of the 14C label from [1-14C]pyruvate into the tricarboxylic acid-cycle intermediates points to a carbon input from pyruvate via enzymes in addition to pyruvate dehydrogenase and citrate synthase. 3. On addition of acetate, the specific radioactivity of citrate showed an initial maximum at 2 min, with a subsequent decline in labelling. The C-6 of citrate (which is removed in the isocitrate dehydrogenase reaction) and the remainder of the molecule showed differential labelling kinetics, the specific radioactivity of C-6 declining more rapidly. Since this carbon is lost in the isocitrate dehydrogenase reaction, the results are consistent with a rapid inactivation of pyruvate dehydrogenase after the addition of acetate, which was confirmed by measuring the 14CO2 production from [1-14C]pyruvate. 4. The results can be interpreted to show that carboxylation of pyruvate to the C4 compounds of the tricarboxylic acid cycle occurs under conditions necessitating anaplerosis in rat myocardium, although the results do not identify the enzyme involved. 5. The specific radioactivity of tissue lactate was too low to allow it to be used as an indicator of the specific radioactivity of the intracellular pyruvate pool. The specific radioactivity of alanine was three times that of lactate. When the hearts were perfused with [1-14C]lactate, the specific radioactivity of alanine was 70% of that of pyruvate. The results suggest that a subcompartmentation of lactate and pyruvate occurs in the cytosol.

scholarly journals The conversion of alanine into glutamine in guinea-pig renal cortex. Essential role of pyruvate carboxylase

1981 ◽  
Vol 200 (1) ◽  
pp. 27-33 ◽  
Author(s):  
M Forissier ◽  
G Baverel
Keyword(s):  
Glutamine Synthetase ◽  
Guinea Pig ◽  
Pyruvate Carboxylase ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Kidney Cortex ◽  
Acid Cycle ◽  
Ammonia Release ◽  
Tricarboxylic Acid Cycle Intermediates

1. The metabolism of L-alanine was studied in isolated guinea-pig kidney-cortex tubules. 2. In contrast with previous conclusions of Krebs [(1935) Biochem. J. 29, 1951-1969], glutamine was found to be the main carbon and nitrogenous product of the metabolism of alanine (at 1 and 5 mM). Glutamate and ammonia were only minor products. 3. At neither concentration of alanine was there accumulation of glucose, glycogen, pyruvate, lactate, aspartate or tricarboxylic acid-cycle intermediates. 4. Carbon-balance calculations and the release of 14CO2 from [U-14C]alanine indicate that oxidation of the alanine carbon skeleton occurred at both substrate concentrations. 5. A pathway involving alanine aminotransferase, glutamate dehydrogenase, glutamine synthetase, pyruvate dehydrogenase, pyruvate carboxylase and enzymes of the tricarboxylic acid cycle is proposed for the conversion of alanine into glutamine. 6. Strong evidence for this pathway was obtained by: (i) suppressing alanine removal by amino-oxyacetate, and inhibitor of transaminases, (ii) measuring the release of 14CO2 from [1-14C]alanine, (iii) the use of L-methionine DL-sulphoximine, an inhibitor of glutamine synthetase, which induced a large increase in ammonia release from alanine, and (iv) the use of fluoroacetate, an inhibitor of aconitase, which inhibited glutamine synthesis with concomitant accumulation of citrate from alanine. 7. In this pathway, the central role of pyruvate carboxylase, which explains the discrepancy between our results and those of Krebs (1935), was also demonstrated.

scholarly journals Triheptanoin partially restores levels of tricarboxylic acid cycle intermediates in the mouse pilocarpine model of epilepsy

2013 ◽  
Vol 129 (1) ◽  
pp. 107-119 ◽  
Author(s):  
Mussie G. Hadera ◽  
Olav B. Smeland ◽  
Tanya S. McDonald ◽  
Kah Ni Tan ◽  
Ursula Sonnewald ◽  
...  
Keyword(s):  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Acid Cycle ◽  
Pilocarpine Model ◽  
Tricarboxylic Acid Cycle Intermediates

scholarly journals Metabolic phases during the development of granulation tissue

1967 ◽  
Vol 105 (1) ◽  
pp. 333-341 ◽  
Author(s):  
Kirsti Lampiaho ◽  
E. Kulonen
Keyword(s):  
Granulation Tissue ◽  
Collagen Synthesis ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Pentose Phosphate ◽  
Acid Cycle ◽  
Short Period ◽  
Tricarboxylic Acid Cycle Intermediates ◽  
Observation Period

1. The metabolism of incubated slices of sponge-induced granulation tissue, harvested 4–90 days after the implantation, was studied with special reference to the capacity of collagen synthesis and to the energy metabolism. Data are also given on the nucleic acid contents during the observation period. Three metabolic phases were evident. 2. The viability of the slices for the synthesis of collagen was studied in various conditions. Freezing and homogenization destroyed the capacity of the tissue to incorporate proline into collagen. 3. Consumption of oxygen reached the maximum at 30–40 days. There was evidence that the pentose phosphate cycle was important, especially during the phases of the proliferation and the involution. The formation of lactic acid was maximal at about 20 days. 4. The capacity to incorporate proline into collagen hydroxyproline in vitro was limited to a relatively short period at 10–30 days. 5. The synthesis of collagen was dependent on the supply of oxygen and glucose, which latter could be replaced in the incubation medium by other monosaccharides but not by the metabolites of glucose or tricarboxylic acid-cycle intermediates.

The Ethylmalonyl-CoA Pathway for Methane-based Biorefineries: A Case Study of Using Methylosinus trichosporium OB3b, an Alpha-proteobacterial Methanotroph, for Producing 2-Hydroxyisobutyric Acid and 1,3-Butanediol from Methane

2021 ◽  
Author(s):  
Dung Hoang Anh Mai ◽  
Thu Thi Nguyen ◽  
Eun Yeol Lee
Keyword(s):  
Carbon Metabolism ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Methylosinus Trichosporium Ob3b ◽  
Methylosinus Trichosporium ◽  
Acid Cycle ◽  
Hydroxyisobutyric Acid ◽  
Tricarboxylic Acid Cycle Intermediates ◽  
Alpha Proteobacteria

The ethylmalonyl-CoA pathway is one of three known anaplerotic pathways that replenish tricarboxylic acid cycle intermediates and plays a major role in the carbon metabolism of many alpha-proteobacteria including Methylosinus...

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