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)

Oleate (0.35 and 1.5 mM) decreases, in a concentration-dependent manner, lactate and pyruvate concentrations in hepatocytes, isolated from fed rats, incubated without exogenous substrate. The glycolytic flux, estimated at 18 mM-glucose by [6-3H]-glucose detritiation and apparent production of lactate and pyruvate, is decreased by oleate. The measurement of glycolytic intermediates shows a cross-over at the phosphofructokinase level, which might result from an increased citrate concentration. All those effects are dependent on oleate oxidation in mitochondria, since they are suppressed by 1 microM-2-[5-(4-chlorophenyl)pentyl]oxiran-2-carboxylate (POCA), an inhibitor of the mitochondrial entry of oleate, but not of its uptake by hepatocytes. The decrease of lactate and pyruvate also results from an oleate-induced enhancement of pyruvate utilization by hepatocytes, as shown by the increase of 14CO2 formation from [1-14C]- and [3-14C]-pyruvate, especially at low (0.4 mM) pyruvate concentration. Those oleate effects are also suppressed by POCA. They might be due to an enhanced flux through pyruvate carboxylase and pyruvate dehydrogenase, as a result of an oleate-induced increase in the mitochondrial concentrations of pyruvate and acetyl-CoA. Thus oleate oxidation inhibits production of lactate and pyruvate in fed-rat hepatocytes, as it does in other tissues. But, in the liver, it also enhances the mitochondrial utilization of pyruvate. The physiological implications of those findings are discussed.
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PMID:Influence of oleate oxidation on pyruvate production and utilization in hepatocytes isolated from fed rats. Effect of 2-[5-(4-chlorophenyl)pentyl]oxiran-2-carboxylate. 647 18

In hepatocytes isolated from fed rats, physiological concentrations of oxalate lower the flux through the tricarboxylic acid cycle (-48%) and reduce the steady-state levels of oxaloacetate and other Krebs cycle intermediates. All the metabolic modifications observed are explained by pyruvate carboxylase inhibition, since oxalate hardly modifies the flux through pyruvate dehydrogenase.
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PMID:Influence of oxalate on the rate of the tricarboxylic acid cycle in rat hepatocytes. 661 92

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

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

Several mutants aspergillus nidulans defective in carbohydrate metabolism were tested for growth on different carbon sources. D-Galacturonate was found to be a substrate, useful to discriminate between mutants in pyruvate kinase, pyruvate dehydrogenase complex or pyruvate carboxylase. The results of these tests indicate how particular classes of mutants can be obtained and which substrates can be used preferentially for a rapid phenotypical screening of unknown mutants.
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PMID:Growth characteristics of Aspergillus nidulans mutans defective in carbohydrate metabolism. 675 Dec 21

In a patient with the clinical symptoms of Leigh's disease a partial deficiency of hepatic pyruvate carboxylase and pyruvate decarboxylase was found at necropsy. Cerebral pyruvate decarboxylase activity was also diminished. All enzyme activities were measured in total homogenates. The finding of typical necrotic lesions in the brain stem was consistent with the clinical diagnosis. During life moderate lactic acidaemia and no hypoglycaemia were observed, but an abnormal organic acid excretion pattern was present. The contribution of the enzyme defects to the aetiology of the disease is discussed.
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PMID:Leigh's disease with decreased activities of pyruvate carboxylase and pyruvate decarboxylase. 679 55

The mechanism of inhibition of pyruvate carboxylase, pyruvate dehydrogenase, and carbamyl phosphate synthetase induced by alpha-ketoisovalerate metabolism has been investigated in isolated rat hepatocytes incubated with lactate, pyruvate, ammonia, and ornithine as substrates. Half-maximum inhibitions of flux through each of these enzyme steps were obtained with 0.3 mM alpha-ketoisovalerate. The inhibition of pyruvate carboxylase flux by alpha-ketoisovalerate was largely reversed by oleate addition, but pyruvate dehydrogenase flux was inhibited further. Inhibition of flux through pyruvate carboxylase could be attributed mainly to the fall of its allosteric activator, acetyl-CoA, with some additional effect due to inhibition by methylmalonyl-CoA. Tissue acetyl-CoA levels decrease as a result of an inhibition of the active form of pyruvate dehydrogenase. Kinetic studies with the purified pig heart pyruvate dehydrogenase complex showed that methyl-malonyl-CoA, propionyl-CoA, and isobutyryl-CoA were inhibitory, the latter noncompetitive with CoASH with an apparent Ki of 90 microM. The observed inhibition of pyruvate dehydrogenase flux correlated with increases of the acetyl-CoA/CoASH and propionyl-CoA/CoASH ratios and isobutyryl-CoA levels, while increases of the mitochondrial NADH/NAD+ ratio explained differences between the effects of alpha-ketoisovalerate and propionate. Carbamyl phosphate synthetase I purified from rat liver was shown to be inhibited directly by methylmalonyl-CoA (apparent Ki of 5 mM). Inhibition of flux through carbamyl phosphate synthetase during alpha-ketoisovalerate metabolism could be attributed both to a direct inhibitory effect of methyl-malonyl-CoA and to a diminished activation by N-acetylglutamate. Direct effects of various acyl-CoA metabolites on these key enzymes may explain symptoms of hypoglycemia and hyperammonemia observed in patients with inherited disorders of organic acid metabolism.
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PMID:Interactions between alpha-ketoisovalerate metabolism and the pathways of gluconeogenesis and urea synthesis in isolated hepatocytes. 683 25

A case of Leigh's syndrome (subacute necrotizing encephalomyelopathy, SNE), proven by autopsy, was reported. The persistent elevation of pyruvate and lactate in blood and hyperalanemia suggested an impairment of pyruvate oxidation, but the enzyme activities of pyruvate dehydrogenase (PDH) and pyruvate carboxylase (PC) in liver tissues of the patient revealed normal. It is postulated that Leigh's syndrome and both enzyme deficiencies are distinct entities.
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PMID:Normal activities of hepatic pyruvate dehydrogenase and pyruvate carboxylase in Leigh's syndrome. 683 60

The respective effects of 2-chloropropionate and dichloroacetate on the pyruvate metabolic crossroads, lipogenesis and ketogenesis, were compared in hepatocytes isolated from fed rats. 2-Chloropropionate acts as an exclusive pyruvate dehydrogenase activator: it increases ketogenesis, lipogenesis, Krebs cycle intermediates and mitochondrial NADH/NAD+ ratio. The effects of dichloroacetate depend on experimental conditions and the intensity of its catabolization into oxalate: the resultant action of dichloroacetate on tested parameters combines the effects of pyruvate dehydrogenase activation on the one hand, and pyruvate carboxylase inhibition by oxalate on the other. A mixture of 2-chloropropionate plus oxalate mimics the effects of dichloroacetate. In hepatocytes from fed rats, endogenous lipogenesis is correlated with the mitochondrial NADH/NAD+ ratio, irrespective of the effector added.
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PMID:Comparison of the effects of 2-chloropropionate and dichloroacetate on ketogenesis and lipogenesis in isolated rat hepatocytes. 688 65

Two patients, one dying at 25 days and one at 20 months had 'chronic' lactic acidaemia with a high lactate to pyruvate ratio. Both showed EEG abnormalities and seizure activity and both died of respiratory failure. Investigation of cultured skin fibroblasts from these patients revealed normal pyruvate dehydrogenase and pyruvate carboxylase activities but the cells showed a decreased ability to oxidase pyruvate which was returned to normal on the addition of methylene blue. Subsequent investigations revealed that the mitochondria from the patients' cells could oxidase pyruvate normally but that the cells had an abnormal NAD to NADH ratio under standard conditions of incubation. It was concluded that both children had a redox disequilibrium in the cytoplasmic compartment due to a problem in transporting reducing equivalents from the cytoplasmic to the mitochondrial compartments.
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PMID:Lactic acidosis, neurological deterioration and compromised cellular pyruvate oxidation due to a defect in the reoxidation of cytoplasmically generated NADH. 688 92


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