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:4.1.1.32 (phosphoenolpyruvate carboxykinase)
4,204 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Tryptophan was administered to rats under various nutritional conditions: fasted for 24 hr, fasted and refed with glucose or corn-oil, fasted and administered glycerol intramuscularly, and nonfasted. 2. The changes in the contents of glycolytic intermediates in the livers indicated that the phosphoenolpyruvate carboxykinase [EC 4.1.1.32] reaction is inhibited by tryptophan administration in all groups of rats. The inversely related changes in the contents of malate and phosphoenolpyruvate were associated with the accumulation of quinolinate in the livers. The content of quinolinate which exhibited the half-maximal effect on the contents of both metabolites was 0.1-0.2 mumole per g liver. 3. The rate of incorporation of 3H from 3H2O into the total hepatic fatty acids was increased about 2-fold by the administration of this amino acid to the fasted rats. The enhancement of the rate was closely related to the increase in the citrate content. The hyperlipogenesis was also related to the decrease of acetyl-CoA and the increase of malonyl-CoA. The content of long-chain acyl-CoA was not affected. These effects of tryptophan administration on the hepatic fatty acid metabolism were found in all groups of rats. The liver content of glycerol 3-phosphate was decreased by tryptophan administration was markedly increased by glycerol injection. The injection of glycerol into the control and the tryptophan-treated rats produced a marked increase of glycerol 3-phosphate but did not affect the rate of fatty acid synthesis in the livers of either group. 4. It may be concluded that, in the livers of rats under various nutritional conditions, the short-term control of fatty acid synthesis by tryptophan administration is most likely due to the activation of acetyl-coenzyme A carboxylase [EC 6.4.1.2] by citrate.
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PMID:The effect of tryptophan administration on fatty acid synthesis in the livers of rats under various nutritional conditions. 0 Mar 75

In alloxan diabetic rats a stimulatory effect of stress on the activity of liver phosphoenolpyruvate carboxykinase seems to be very likely. In intact animals the inhibitory effect of glucose feeding (15% glucose instead of laboratory diet and water) on the activity of liver tyrosine aminotransferase (TAT) and tryptophan pyrrolase was reconfirmed. Moreover, a reversal of this effect by immobilization for 2.5 h was observed. After a mean intake of 5.3 g glucose/100 g body weight during 16 h this reversal was only partial and after 3.4 glucose/100 g during the same time the glucose effect was abolished. Stimulation of both enzymes by corticosterone and of TAT by stress-induced release of glucagon may play a role in this reversal.
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PMID:Inhibitory effect of immobilization stress on depression of liver tyrosine aminotransferase and tryptophan pyrrolase by glucose feeding in rats. 1 21

In adult male rats kept under controlled illumination (lights on from 6 a.m.--6 p.m.) the existence of higher afternoon values of plasma corticosterone ("B") is reconfirmed. Moreover, plasma "B" increases induced by 400 revolutions in Noble-Collip drums or immobilization for 2.5 h were found substantially less pronounced if stressor application took place at 4 p.m. rather than 8 a.m. so that essentially no difference between morning and afternoon poststress peaks was observed. Also the response to 0.05 mg ACTH i.p. was smaller in the afternoon experiments. Additionally three liver enzymes the activity of which is increased by corticosterone released under conditions of stress were also studied. Higher afternoon activity of liver tyrosine aminotransferase (TAT) and tryptophan pyrrolase (TP) was observed in spite of fasting from 8 a.m. imposed to the animals taking part in the afternoon experiments. The activity of phosphoenolpyruvate carboxykinase (PEPCK) was also increased in the afternoon probably because of the food deprivation. Immobilization-induced increase in the activity of all three enzymes showed a similar blunting as plasma "B" response, so that no differences between morning and afternoon were found in peak poststress values. In conclusion, the low plasma "B" response of rats at a time when the animals begin the active part of their day seems to have important metabolic implications.
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PMID:A three hours study of the response of plasma corticosterone and of three liver enzymes in rats subjected to stress in the late afternoon or during the morning hours. 3 35

Carbohydrate metabolism and vitamin-B6 status were assessed before and after pyridoxine administration in 46 women taking combined oestrogen-progestagen oral contraceptives (O.C.). 18 women had evidence of tissue depletion of vitamin B6, although all the women had abnormal tryptophan metabolism, including increased urinary xanthurenic acid (X.A.) excretion. In the women with vitamin B6 deficiency, administration of this vitamin caused elevation of fasting blood-pyruvate levels, and reduction in plasma glucose, insulin, and blood-pyruvate responses after an oral glucose load. These changes in carbohydrate metabolism were not found in the 28 non-vitamin-B6-deficient women. These results indicate that carbohydrate intolerance in women on O.C. is unlikely to be mediated by the formation of a complex of X.A. with insulin, as has formerly been proposed. Since the synthesis of the tryptophan metabolite quinolinic acid, an inhibitor of the heptaic enzyme phosphoenolpyruvate carboxykinase, may be enhanced by the administration of pyridoxine, it is suggested that this metabolite might be the important factor in the improvement of glucose tolerance in the vitamin-B6-deficient women. This conclusion is supported by the improvement in glucose tolerance observed in 6 women on O.C. and in 4 patients with glucocorticoid excess who were not vitamin-B6 deficient, when they were given tryptophan to augment the synthesis of quinolinic acid.
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PMID:Influence of oral contraceptives, pyridoxine (vitamin B6), and tryptophan on carbohydrate metabolism. 5 85

Phosphoenolpyruvate carboxykinase (GTP) was induced by a combination of dibutyryl cyclic AMP, theophyline and dexamethasone in Reuber H35 hepatoma cells under conditions where an amino acid in the medium was replaced by an appropriate analogue. 2. With canavanine replacing arginine or with 5-fluorotryptophan or 6-fluorotryptophan replacing tryptophan the induced enzyme had a lower catalytic activity-relative to antibody reactivity. 3. These aberrant enzyme molecules were heat-labile in vitro. 4. Measurements of enzyme degradation in vivo indicated that the canavanine-containing enzyme and the 6-fluorotryptophan-containing enzyme were degraded more rapidly than the enzyme containing all natural amino acids.
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PMID:Properties of phosphoenolpyruvate carboxykinase (guanosine triphosphate) synthesized in hepatoma cells in the presence of amino acid analogues. 16 22

1. Naturally-occurring and synthetic analogues of phenylalanine, tyrosine, histidine, arginine, proline, tryptophan and the sulphur amino acids have beeen tested in rat reticulocytes and in the Reuber H35 hepatoma for effects on protein synthesis and protein degradation and on the heat lability of phosphoenolpyruvate carboxykinase (EC 4.1.1.32) in the hepatoma cells. The experiments were designed to test whether the analogues could be incorporated into mammalian proteins and whether the resultant proteins would be degraded at an accelerated rate. 2. Several analogues, including thiazolylanine, triazolalanine and selenocystine both stimulated protein synthesis and produced labile protein in reticulocytes. Other analogues, such as dihydroxyphenylalanine, thioproline and pipecolic acid accelerated protein breakdown but probably indirectly via an inhibition of protein synthesis. Azetidine-2-carboxylic acid had the largest effect on protein breakdown in reticulocytes. 3. Labile protein was produced in hepatoma cells incubated in the presence of azetidine-2-carboxylic acid, canavanine, indospicine, triazolalanine, 2-, 3- and 4-fluorophenylalanine. These same analogues, together with 3,4-dehydroproline, beta-2-thienylalanine, dihydroxyphenylalanine, histidinol, 5- and 6-fluorotryptophan, selenocystine and selenomethionine produced heat-labile phosphoenolpyruvate carboxykinase. Enzyme induced in the presence of selenomethionine or indospicine showed the largest increases in heat lability, and for these analogues equimolar concentrations of methionine and arginine respectively were needed to nullify the enzyme abnormality. 4. The toxicity of the same naturally-occurring analogues has been discussed in terms of their ability to be incorporated into cell proteins.
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PMID:Effects of amino acid analogues on protein synthesis and degradation in isolated cells. 21 95

1. Tryptophan inhibition of gluconeogenesis in isolated rat liver cells is characterized by a 20 min lag period before linear rates of glucose output are attained. 2. Half-maximal inhibition of gluconeogenesis in isolated rat hepatocytes is produced by approx. 0.1 mM-tryptophan. 3. Tryptophan inhibits gluconeogenesis from all substrates giving rise to oxaloacetate, but stimulates glycerol-fuelled glucose production. 4. Gluconeogenesis in guinea-pig hepatocytes is insensitive to tryptophan. 5. Changes in metabolite concentrations in rat liver cells are consistent with a locus of inhibition at the step catalysed by phosphoenolpyruvate carboxykinase. 6. Inhibition of gluconeogenesis persists in cells from rats pretreated with tryptophan in vivo. 7. Tryptophan has no effect on urea production from alanine, but decreases [1-14C]palmitate oxidation to 14CO2 and is associated with an increased [hydroxybutyrate]/[acetoacetate] ratio. 8. These results are discussed with reference to the control of gluconeogenesis in various species.
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PMID:Differential effects of tryptophan on glucose synthesis in rats and guinea pigs. 74 54

The inhibitory effects of metabolites of L-tryptophan on gluconeo-genesis in rat renal cortex has been established. 1. Glucose production was inhibitied by quinolinate in vitro. The inhibition is due to the decreased phosphoenolpyruvate carboxykinase activity. As suggested for purified enzyme systems, quinolinate seems to exert its action in tissue slices by chelating divalent metal ions. The minimum effective extracellular concentration of the inhibitor was 5 X 10(-5) M with pyruvate as a precursor for gluconeo-genesis. 2. The effect of 3-hydroxyanthranilate is stronger (minimal effective concentration 10(-5) M) than that of quinolinate. 3-Hydroxyanthranilate may be effective in its original form and/or as a dimer degrandation product. The compound(s) exert a second effect in addition to blocking the phosphoenolpyruvate carboxykinase. This block is attained by conversion of 3-hydroxyanthranilate to quinolinate. The non-quinolinate mediated effect may be due to a reduced ATP regeneration. 3. It is suggested that kidney cortex responds sensitively to disturbances in ATP metabolism by reduction of glucose synthesis, when it is not the result of blocked formation of phosphoenolpyruvate.
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PMID:Inhibition of gluconeogenesis in rat renal cortex slices by metabolites of L-tryptophan in vitro. 115 21

In parenchymal cells from starved mice L-tryptophan is a potent inhibitor of gluconeogenesis from substrates giving rise to oxaloacetate. Quinolinate yields a different pattern of inhibition and is generally much less effective. Tryptamine, indole 3-acetaldehyde and indole 3-acetate are equally as effective as tryptophan. Tryptamine inhibition alone may be overcome by pargyline; serotonin does not prevent the inhibition due to tryptophan. In kidney slices from starved rats, however, tryptophan has no effect on gluconeogenesis. Indole 3-acetate is also relatively ineffective, but quinolinate is signficiantly more potent than in liver; at 0.1mM, glucose production from lactate is 50% inhibited. Quinolinate is less effective with citric acid cycle substrates; the pattern of inhibition is consistent with a direct action on phosphoenolpyruvate carboxykinase. There is no evidence that glutamate dehydrogenase is simultaneously inhibited.
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PMID:Effect of tryptophan and its metabolites on gluconeogenesis in mammalian tissues. 124 97

We report two brothers with a previously undescribed type of mitochondrial encephalomyopathy and associated aminoacidopathy. Both have growth failure, progressive intellectual decline, deafness, neurologic dysfunction, exercise intolerance, lactic acidosis, and abnormal plasma and cerebrospinal fluid amino acid levels (elevated levels of alanine and low levels of threonine, methionine, citrulline, tryptophan, ornithine, arginine, and lysine). A muscle biopsy specimen taken from the younger, more severely affected brother showed abnormal mitochondrial morphology. Activities of the following enzymes in cultured fibroblasts from both boys were normal: pyruvate dehydrogenase, pyruvate carboxylase, phosphoenolpyruvate carboxykinase, cytochrome oxidase, reduced nicotinamide-adenine dinucleotide-cytochrome c reductase, and succinate cytochrome c reductase. Fibroblast mitochondria from the younger boy showed undetectable (less than 1% of control values) adenosine triphosphate synthesis with pyruvate and malate, whereas adenosine triphosphate synthesis with succinate was 70% of control values. These data indicate probably deficient activity of complex I of the electron transport chain. The boys' mother has progressive neurosensory hearing loss; their sister is clinically normal. Both mother and sister have many of the biochemical abnormalities found in the boys. It is possible, but not proved, that this disorder is inherited through maternal mitochondria.
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PMID:Mitochondrial encephalomyopathy with associated aminoacidopathy in a male sibship. 273 99


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