Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:6.4.1.1 (pyruvate carboxylase)
1,516 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Changes of the extra- and intramitochondrial ATP/ADP ratios as a function of the respiratory state were measured in incubations with rat liver mitochondria. ATPase or creatine/creatine kinase was used to change the extramitochondrial ATP/ADP ratio; the separation of the mitochondrial pellet was performed by a Millipore filtration technique. Under all conditions tested, the intramitochondrial ratio changed in the same direction as the extramitochondrial one, except in the presence of atractylate where this correlation was not observed. Furthermore, it could be shown that the oxygen uptake and pyruvate carboxylase activity correlated with the intramitochondrial ATP/ADP ratio and not with the extramitochondrial one. These results do not support the proposal that the adenine nucleotide translocase is rate limiting for respiration.
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PMID:Relation between extra- and intramitochondrial ATP/ADP ratios in rat liver mitochondria. 644 52

The distribution of pyruvate between cell compartments measured in isolated hepatocytes in the presence of lactate was in agreement with delta pH across plasma and mitochondrial membranes. In isolated liver mitochondria NH4Cl decreased the transmembrane potential (delta psi) by about 14 mV, whereas no change of delta pH was observed. In the presence of lactate or alanine NH4Cl increased the mitochondrial pyruvate concentration presumably due to the inhibition of the flux through pyruvate carboxylase. In the presence of lactate or alanine changes in the amount of the active form of pyruvate dehydrogenase (PDHa) were correlated with the mitochondrial pyruvate concentration, NH4Cl increased the amount of PDHa by lowering the mitochondrial ATP/ADP and NADH/NAD+ ratios.
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PMID:The elucidation of the effect of ammonium chloride on pyruvate distribution and pyruvate dehydrogenase interconversion in isolated rat hepatocytes. 646 32

Formycin triphosphate (FTP), a fluorescent analogue of ATP, is a competitive inhibitor of chicken liver pyruvate carboxylase with respect to ATP. The chicken liver enzyme is unable to utilise FTP as a substrate at a measureable rate, but FTP is a poor substrate for the sheep liver enzyme. When FTP binds to the enzyme, its fluorescence is enhanced and in this way the formation of enzyme-FTP complexes can be monitored. Using this property of FTP, the effect of Mg2+ and acetyl-CoA on the binding of nucleoside triphosphates to the chicken liver enzyme was examined. Mg2+ was found to enhance the binding of FTP whilst acetyl-CoA reduced the fluorescence intensity of a mixture of Mg2+, enzyme and FTP. Most probably, this was caused by a conformational change in the enzyme which changed the environment of the fluorophore.
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PMID:Interaction of formycin A-5'-triphosphate with pyruvate carboxylase. 647 36

In newborn rabbit liver the mitochondrial adenine nucleotide pool (ATP + ADP + AMP) size increased from 6.4 +/- 0.4 to 14.5 +/- 0.7 nmol/mg mitochondrial protein within 2 hr after birth. Gluconeogenesis (from lactate) in isolated hepatocytes rose from 13.1 +/- 1.9 at birth to 42.3 +/- 2.4 nmol glucose/min/10(7) cells at 2 hr. Pyruvate carboxylation in isolated mitochondria increased in parallel from 42.8 +/- 4.9 at birth to 108.6 +/- 8.2 nmol H14CO-3/min/mg mitochondrial protein at 2 hr. The similar developmental time course for these three phenomena suggested that the rapid increase in gluconeogenesis might be a result of increased availability of adenine nucleotides to the ATP-requiring mitochondrial enzyme, pyruvate carboxylase. Manipulation of the mitochondrial adenine nucleotide pool size in vitro resulted in predictable changes in the rate of pyruvate carboxylation. We concluded that the postnatal increase in mitochondrial adenine nucleotide content stimulates pyruvate carboxylation, thereby causing a rapid increase in the rate of gluconeogenesis.
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PMID:Regulation of hepatic gluconeogenesis by rapid compartmentation of mitochondrial adenine nucleotides in the newborn rabbit. 669 85

Treatment of rats for 3 h with dexamethasone was shown to stimulate both pyruvate carboxylation and decarboxylation in the subsequently isolated mitochondria. The effect of hormone treatment on pyruvate carboxylation was also apparent in liver homogenates assayed within minutes of killing the animal and was independent of the temperature at which the assay was performed, suggesting that it was not an artifact of the mitochondrial preparation procedure. The stimulation of both aspects of pyruvate metabolism in the intact organelle was independent of the induction of either pyruvate carboxylase or pyruvate dehydrogenase. Similarly, there was no change in the percentage of pyruvate dehydrogenase in the active form, indicating that the effect of steroid treatment on pyruvate oxidation was not via changes in the degree of phosphorylation of the enzyme. Adrenalectomizing the animals for a period of 14 days before the experiment had no effect on either parameter. Glucocorticoid treatment of the animals increased the rate of pyruvate uptake into the mitochondria, as measured by the titration of pyruvate metabolism with alpha-cyano-4-hydroxycinnamate, a specific inhibitor of the pyruvate translocator. It also increased the intramitochondrial concentrations of acetyl-CoA and ATP and led to an elevated [ATP]/[ADP] ratio within the mitochondria. It is suggested that both enzymes of pyruvate metabolism exist in the mitochondria under considerable restraint and that glucocorticoids act to relieve this restraint by alterations in substrate supply and the intramitochondrial concentrations of effector molecules.
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PMID:The stimulation of mitochondrial pyruvate carboxylation after dexamethasone treatment of rats. 672 47

Hepatocytes prepared from rats treated with dexamethasone for 2 or 3h and maintained in the presence of 10 microM-dexamethasone in the preparation and incubation buffers showed significantly elevated rates of gluconeogenesis compared with those prepared from control animals. Dexamethasone treatment also increased the sensitivity of the cells to glucagon and the catecholamines. Analysis of the concentrations of metabolites in the gluconeogenic pathway indicated that dexamethasone decreased the intracellular concentration of pyruvate and increased those of phosphoenolpyruvate, acetyl-CoA and citrate, suggesting a stimulation of the reaction(s) converting pyruvate into phosphoenolpyruvate. This was substantiated by analysis of the pattern of metabolites found in the mitochondrial compartment after digitonin fractionation of the cells. Inclusion of 3-mercaptopicolinate in the incubation enhanced the effect of the hormone on the distribution of metabolites. Thus, in the absence of an effect of the steroid at the level of phosphoenolpyruvate carboxykinase or pyruvate kinase, dexamethasone treatment still increased the formation of malate, aspartate and citrate from pyruvate, indicating a stimulation in the intact cell of pyruvate carboxylase. It is suggested that the stimulation of pyruvate carboxylase is a result of a general activation of mitochondrial function, with an increase in the intramitochondrial concentrations of acetyl-CoA and ATP, a decrease in glutamate and an enhanced intramitochondrial [ATP]/[ADP] ratio.
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PMID:Effect of treatment of rats with dexamethasone in vivo on gluconeogenesis and metabolite compartmentation in subsequently isolated hepatocytes. 672 48

The effect of long-chain acyl-CoA on subcellular adenine nucleotide systems was studied in the intact liver cell. Long-chain acyl-CoA content was varied by varying the nutritional state (fed and starved states) or by addition of oleate. Starvation led to an increase in the mitochondrial and a decrease in the cytosolic ATP/ADP ratio in liver both in vivo and in the isolated perfused organ as compared with the fed state. The changes were reversed on re-feeding glucose in liver in vivo or on infusion of substrates (glucose, glycerol) in the perfused liver, respectively. Similar changes in mitochondrial and cytosolic ATP/ADP ratios occurred on addition of oleate, but, importantly, not with a short-chain fatty acid such as octanoate. It is concluded that long-chain acyl-CoA exerts an inhibitory effect on mitochondrial adenine nucleotide translocation in the intact cell, as was previously postulated in the literature from data obtained with isolated mitochondria. The physiological relevance with respect to pyruvate metabolism, i.e. regulation of pyruvate carboxylase and pyruvate dehydrogenase by the mitochondrial ATP/ADP ratio, is discussed.
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PMID:Effect of long-chain fatty acyl-CoA on mitochondrial and cytosolic ATP/ADP ratios in the intact liver cell. 674 76

Administration of physiologically low doses of bicarbonate into rats caused an inhibition of oxidative phosphorylation and a transitory decrease in ATP content in liver mitochondria; at the same time, concentrations of malate and glutamate were unaltered and those of pyruvate and phosphoenolpyruvate were decreased. Insulin removed the bicarbonate effect on mitochondrial functions but affected only slightly the distribution of metabolites. Bicarbonate appears to activate pyruvate carboxylase and to inhibit succinate dehydrogenase as well as the operation of tricarboxylic acid cycle due to accumulation of oxaloacetate. The effect of insulin mimics acceleration of decarboxylation reactions in mitochondria.
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PMID:[Effect of bicarbonate and insulin on energy metabolism in the mitochondria of rat liver]. 676 May 41

Oxygen uptake in skeletal muscle mitochondria respiring on pyruvate or on acetylcarnitine plus propionylcarnitine is stimulated 3--4-fold by bicarbonate. The stimulation is highly dependent on ATP. The respiration rate obtained amounts to 1/4-1/3 of the rate obtained with pyruvate-malate in the presence of ADP. With decreasing ATP/ADP ratios in the medium, a decreasing stimulation by bicarbonate is obtained. Similar results were obtained with heart mitochondria. With ATP added, a pyruvate-dependent build up of citric acid cycle intermediates takes place in incubations with skeletal muscle mitochondria amounting to about 0.5 nmol x min-1 x mg protein-1. In 14CO2-fixation experiments, the activity of pyruvate carboxylase (EC 6.4.2.1) amounts to about 3 nmol x min-1 x mg protein-1 under similar conditions. With propionylcarnitine plus acetylcarnitine a similar stimulation of respiration and fixation of bicarbonate is observed. In this case the respiration and the propionyl-CoA carboxylase (EC 6.4.1.3) is less inhibited by ADP. The results are discussed in relation to the regulation of the level of citric acid cycle intermediates in muscle tissues. It is concluded that pyruvate carboxylase is an important anaplerotic enzyme in skeletal muscle mitochondria.
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PMID:Pyruvate carboxylase and propionyl-CoA carboxylase as anaplerotic enzymes in skeletal muscle mitochondria. 677 58

Pyruvate carboxylase from Pseudomonas citronellolis is composed of non-identical subunits which include a larger biotin-containing polypeptide (alpha) of Mr = 65,000, and a smaller biotin-free polypeptide (beta) of Mr = 54,000. We have investigated these two polypeptides by analyzing their amino acid composition, cyanogen bromide peptide maps, and immunochemistry. The results showed that the subunits of the enzyme have quite different properties. Antibodies prepared against the polypeptides were used as probes of the catalytic functions of the subunits. Immunotitration studies indicated that only anti-alpha inhibited enzyme activity. The antibiotin fraction of this antibody population was removed by passage through biotin-Sepharose (anti-alpha'). Titration curves using anti-alpha' showed identical inhibition when total pyruvate carboxylase activity, ATP/Pi exchange activity, and pyruvate/oxalacetate exchange activity were measured, suggesting that both active sites are located on the alpha polypeptide. The arrangement of the subunits in the quaternary structure was investigated by means of the surface probe carbonic anhydrase linked to toluene isocyanate, and by partial digestion experiments with trypsin, chymotrypsin, and pronase. The results indicated that the alpha polypeptides are on the outside of the molecule and the beta polypeptides are the internal subunits.
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PMID:Characterization of the subunit structure of pyruvate carboxylase from Pseudomonas citronellolis. 679 93


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