scholarly journals A Mitochondrial Pyruvate Carrier Required for Pyruvate Uptake in Yeast,Drosophila, and Humans

Science ◽  
2012 ◽  
Vol 337 (6090) ◽  
pp. 96-100 ◽  
Author(s):  
Daniel K. Bricker ◽  
Eric B. Taylor ◽  
John C. Schell ◽  
Thomas Orsak ◽  
Audrey Boutron ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Mitochondrial Membrane ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Inner Mitochondrial Membrane ◽  
Pyruvate Metabolism ◽  
Genetic Studies ◽  
Mitochondrial Pyruvate Carrier ◽  
Families With Children ◽  
Tricarboxylic Acid Cycle Intermediates

Pyruvate constitutes a critical branch point in cellular carbon metabolism. We have identified two proteins, Mpc1 and Mpc2, as essential for mitochondrial pyruvate transport in yeast,Drosophila, and humans. Mpc1 and Mpc2 associate to form an ~150-kilodalton complex in the inner mitochondrial membrane. Yeast andDrosophilamutants lackingMPC1display impaired pyruvate metabolism, with an accumulation of upstream metabolites and a depletion of tricarboxylic acid cycle intermediates. Loss of yeast Mpc1 results in defective mitochondrial pyruvate uptake, and silencing ofMPC1orMPC2in mammalian cells impairs pyruvate oxidation. A point mutation inMPC1provides resistance to a known inhibitor of the mitochondrial pyruvate carrier. Human genetic studies of three families with children suffering from lactic acidosis and hyperpyruvatemia revealed a causal locus that mapped toMPC1, changing single amino acids that are conserved throughout eukaryotes. These data demonstrate that Mpc1 and Mpc2 form an essential part of the mitochondrial pyruvate carrier.

scholarly journals Functional features and genomic organization of mouse NaCT, a sodium-coupled transporter for tricarboxylic acid cycle intermediates

2004 ◽  
Vol 378 (3) ◽  
pp. 949-957 ◽  
Author(s):  
Katsuhisa INOUE ◽  
You-Jun FEI ◽  
Lina ZHUANG ◽  
Elangovan GOPAL ◽  
Seiji MIYAUCHI ◽  
...  
Keyword(s):  
Transport Process ◽  
Mammalian Cells ◽  
Tricarboxylic Acid Cycle ◽  
Expression System ◽  
Tricarboxylic Acid ◽  
Activation Process ◽  
Xenopus Laevis Oocyte ◽  
Acid Cycle ◽  
Functional Features ◽  
Tricarboxylic Acid Cycle Intermediates

In the present study, we report on the molecular cloning and functional characterization of mouse NaCT (Na+-coupled citrate transporter), the mouse orthologue of Drosophila Indy. Mouse NaCT consists of 572 amino acids and is highly similar to rat and human NaCTs in primary sequence. The mouse nact gene coding for the transporter is approx. 23 kb long and consists of 12 exons. When expressed in mammalian cells, the cloned transporter mediates the Na+-coupled transport of citrate and succinate. Competition experiments reveal that mouse NaCT also recognizes other tricarboxylic acid cycle intermediates such as malate, fumarate and 2-oxo-glutarate as excellent substrates. The Michaelis–Menten constant for the transport process is 38±5 µM for citrate and 37±6 µM for succinate at pH 7.5. The transport process is electrogenic and exhibits an obligatory requirement for Na+. Na+-activation kinetics indicates that multiple Na+ ions are involved in the activation process. Extracellular pH has a differential effect on the transport function of mouse NaCT depending on whether the transported substrate is citrate or succinate. The Michaelis–Menten constants for these substrates are also influenced markedly by pH. When examined in the Xenopus laevis oocyte expression system with the two-microelectrode voltage-clamp technique, the transport process mediated by mouse NaCT is electrogenic. The charge-to-substrate ratio is 1 for citrate and 2 for succinate. The most probable transport mechanism predicted by these studies involves the transport of citrate as a tervalent anion and succinate as a bivalent anion with a fixed Na+/substrate stoichiometry of 4:1. The present study provides the first unequivocal evidence for the electrogenic nature of mammalian NaCT.

scholarly journals Regulation of pyruvate metabolism via pyruvate carboxylase in rat brain mitochondria

1973 ◽  
Vol 132 (2) ◽  
pp. 185-192 ◽  
Author(s):  
Mulchand S. Patel ◽  
Shirley M. Tilghman
Keyword(s):  
Rat Brain ◽  
Pyruvate Carboxylase ◽  
Inorganic Phosphate ◽  
Citrate Synthase ◽  
Tricarboxylic Acid Cycle ◽  
Brain Mitochondria ◽  
Tricarboxylic Acid ◽  
Pyruvate Metabolism ◽  
Rat Brain Mitochondria ◽  
Tricarboxylic Acid Cycle Intermediates

1. The fixation of CO2 by pyruvate carboxylase in isolated rat brain mitochondria was investigated. 2. In the presence of pyruvate, ATP, inorganic phosphate and magnesium, rat brain mitochondria fixed H14CO3- into tricarboxylic acid-cycle intermediates at a rate of about 250nmol/30min per mg of protein. 3. Citrate and malate were the main radioactive products with citrate containing most of the radioactivity fixed. The observed rates of H14CO3- fixation and citrate formation correlated with the measured activities of pyruvate carboxylase and citrate synthase in the mitochondria. 4. The carboxylation of pyruvate by the mitochondria had an apparent Km for pyruvate of about 0.5mm. 5. Pyruvate carboxylation was inhibited by ADP and dinitrophenol. 6. Malate, succinate, fumarate and oxaloacetate inhibited the carboxylation of pyruvate whereas glutamate stimulated it. 7. The results suggest that the metabolism of pyruvate via pyruvate carboxylase in brain mitochondria is regulated, in part, by the intramitochondrial concentrations of pyruvate, oxaloacetate and the ATP:ADP ratio.

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...

Determination of gluconeogenesis in vivo with 14C-labeled substrates

1985 ◽  
Vol 248 (4) ◽  
pp. R391-R399 ◽  
Author(s):  
J. Katz
Keyword(s):  
Pyruvate Carboxylase ◽  
Tricarboxylic Acid Cycle ◽  
Specific Radioactivity ◽  
Tricarboxylic Acid ◽  
Pyruvate Metabolism ◽  
Acetyl Coenzyme A ◽  
Glucose Carbon ◽  
Labeling Pattern

A mitochondrial model of gluconeogenesis and the tricarboxylic acid cycle, where pyruvate is metabolized via pyruvate carboxylase and pyruvate dehydrogenase, and pyruvate kinase is examined. The effect of the rate of tricarboxylic acid flux and the rates of the three reactions of pyruvate metabolism on the labeling patterns from [14C]pyruvate and [24C]acetate are analyzed. Expressions describing the specific radioactivities and 14C distribution in glucose as a function of these rates are derived. Specific radioactivities and isotopic patterns depend markedly on the ratio of the rates of pyruvate carboxylation and decarboxylation to the rate of citrate synthesis, but the effect of phosphoenolpyruvate hydrolysis is minor. The effects of these rates on 1) specific radioactivity of phosphoenolpyruvate, 2) labeling pattern in glucose, and 3) contribution of pyruvate, acetyl-coenzyme A, and CO2 to glucose carbon are illustrated. To determine the contribution of lactate or alanine to gluconeogenesis, experiments with two compounds labeled in different carbons are required. Methods in current use to correct for the dilution of 14C in gluconeogenesis from [14C]pyruvate are shown to be erroneous. The experimental design and techniques to determine gluconeogenesis from 14C-labeled precursors are presented and illustrated with numerical examples.

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).

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