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)

Neonatal hypoglycemia is of frequent occurrence in fasted newborn babies or animals but the origin of this hypoglycemia is not fully understood. Studies performed in newborn rats have shown that liver glycogenolysis and gluconeogenesis occur immediately after birth and that the increase in the activities of key regulatory enzymes (phosphorylase, glycogen synthetase and phosphoenolpyruvate carboxykinase) results probably from the rise of plasma glucagon and the fall of plasma insulin induced by the "stress" of birth. When the liver glycogen stores have been exhausted, i.e. between 6 and 16 hours after birth, a profound hypoglycemia develops in fasting newborn rats. The inability of hepatic gluconeogenesis to produce sufficient glucose to meet the energy requirement of the newborn tissues results from a lack of fat-derived (free fatty acids and ketone bodies) and gluconeogenic (lactate, amino acids) substrates. The stage of appearance and the mechanisms regulating gluconeogenesis in other species including human are discussed.
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PMID:[Energy metabolism in the perinatal period (author's transl)]. 18 42

The effects of chronic oral ingestion of lead in doses ranging from 20-80 ppm were compared with those seen after the subacute exposure of rats to a 10 mg/kg daily dose of the heavy metal for 7 days. Irrespective of the treatment regimen used, lead treatment significantly increased the activities of renal pyruvate carboxylase, phosphoenolpyruvate carboxykinase, fructose 1,6-diphosphatase and glucose 6-phosphatase. The observed enhancement of kidney gluconeogenic enzymes in chronically treated animals was associated with a stimulation of the adenylate cyclase-cyclic AMP system, a rise in blood blucose and urea as well as a depression in hepatic glycogen and serum immunoreactive insulin (IRI) levels. In contrast, subacute exposure to lead failed to significantly alter cyclic AMP metabolism and the concentrations of liver glycogen, blood glucose, serum urea or IRI. Whwereas the insulinogenic index (the ratio of serum IRI to blood glucose concentration) was markedly suppressed in chronically treated rats, this ratio remained within normal limits following subacute exposure to the heavy metal. However, a marked decrease in the insulinogenic index was observed in subacutely treated rats 15 min after the administration of a glucose load. The data provide evidence to show that increased glucose synthesis as well as suppressed pancreatic function may be responsible for lead-induced disturbances in glucose homeostasis.
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PMID:Effects of subsacute and chronic lead treatment on glucose homeostasis and renal cyclic AMP metabolism in rats. 18 14

1. The development of glycerolkinase before and after birth was investigated in liver and kidney of rat and hamster. In rat liver, enzyme activity increased very slowly before birth and rapidly thereafter, reaching adult values at the 6th day of postnatal life. In hamster liver, glycerolkinase was considerably elevated already in utero, increased dramatically within the 1st day of postnatal life and reached adult values at the end of the 1st week. The development of hepatic glycerolkinase was compared with that of hepatic phosphoenolpyruvate carboxykinase of rat and hamster up to the 20th day of postnatal life. The different time-courses of the levels of these two enzymes before and after birth as well as the known kinetics of serum insulin, glucagon and corticosterone during that time suggested that none of these hormones is involved in the perinatal development of hepatic glycerolkinase activity. In contrast to liver, kidney glycerolkinase activity in both, rat and hamster, showed a delayed increase during the first week of postnatal life followed by a more pronounced elevation to adult values within the following 2 weeks. 2. When liver and kidney glycerolkinase activity was investigated during starvation (+/- refeeding), in alloxan diabetes(+/- insulin) and after adrenalectomy (+/- cortisol) no significant change in enzyme activity per g tissue could be detected either in liver or in kidney. However, total hepatic glycerolkinase activity was diminished during starvation as a consequence of decreasing liver weight. 3. Incorporation of U-[14C]-glycerol into CO2, lipids and glucose + glycogen by rat liver and kidney cortex slices was studied under the above gluconeogenetic conditions. Despite unchanged glycerolkinase activity in both organs, gluconeogenesis from glycerol was enhanced during starvation and in chronic alloxan diabetes, and could be reversed by refeeding and insulin replacement, respectively. 4. Feeding 20% of linolic acid to normal, alloxan-diabetic or adrenalectomized rats resulted in a significant increase in glycerolkinase activity in liver but not in kidney. 5. From the present findings it is suggested that the first step of gluconeogenesis from glycerol in liver and kidney is not influenced by glucagon, insulin and glucocorticoids, which are generally believed to regulate the rate of gluconeogenesis from non-glycerol precursors, but probably by the change in blood glycerol concentration.
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PMID:Glycerolkinase--a regulatory enzyme of gluconeogenesis? 18 91

In different metabolic states renal phosphoenolpyruvate carboxykinase (PEP-CK) activities are closely correlated with in vitro glucogenic rates, suggesting a limitation of the glucogenic capacity of kidney by this enzyme. Stimulation of renal gluconeogenesis from pyruvate, lactate, and succinate by lysine and glutamine was therefore associated with a regulatory attack of these amino acids at the level of PEP-carboxykinase. This postulate was confirmed by the failure of lysine to stimulate glucose synthesis from fructose. Experimental support for an interference of glutamine and PEP-carboxykinase was obtained by a study on the inactivation of this enzyme in kidney cortex homogenates: A rapid inactivation of enzyme activity within 40-50 min could be slowed down by glutamine. In addition the inactivation was counteracted by ATP. At suboptimal concentrations of the trinucleotide its effect was potentiated by c-AMP and c-GMP. Studies on the effect of ATP on PEP-carboxykinase in kidney cortex homogenates from rats in different metabolic states revealed: In homogenates from carbohydrate fed animals extreme low activities of PEP-CK were not altered by ATP, whereas elevated enzyme activities after a protein rich diet could be further raised by a factor of 2 or 3 by ATP. GTP and ITP could substitute for ATP. An extension of these studies on hepatic enzymes showed a similar inactivation of tyrosine aminotransferase (TAT) and a protective effect of ATP. The data obtained from these experiments favour an interconversion of PEP-carboxykinase and tyrosine aminotransferase into different forms as possible mechanism for their regulation.
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PMID:Regulation of phosphoenolpyruvate carboxykinase by glutamine and ATP as possible control mechanisms of renal gluconeogenesis. 18 82

The mechanism of the interaction between glucocorticoids and cyclic AMP in the regulation of phosphoenolpyruvate carboxykinase (GTP: oxalocetate carboxylase, transphosphorylating, EC 4.1.1.32) was investigated in the isolated perfused rat liver using inhibitors of transcription or translation. Dibutyryl cyclic AMP produced a rapid increase in P-enolpyruvate carboxykinase activity. The response of the enzyme to the cyclic nucleotide ceased however, at 4 h, but was restored by dexamethasone. The dibutyryl cyclic AMP-induced increase in P-enolpyruvate carboxykinase activity was completely blocked by cycloheximide, but not not by cordycepin. However, cordycepin totalaly suppressed the "permissive" effect of dexamethasone on the response of the enzyme to dibutyryl cyclic AMP. Preperfusion of the livers with dexamethasone and cycloheximide, following by perfusion without the steroid hormone and the inhibitor, resulted in a rapid rise in P-enolpyruvate carbosykinase activity, which was not affect by cordycepin. If livers were preperfused with cordycepin for different time-periods, followed by dibutyryl cyclic AMP stimulation of P-enolpyruvate carboxykinase synthesis, the response of the enzyme to the cyclic nucleotide was progressively reduced, achieving 50% inhibition after 1.5 h of preperfusion. These results suggest that the induction of hepatic P-enolpyruvate carboxykinase to maximum values, brought about by cyclic AMP at the level of translation, depends on the supply of newly synthetized mRNA provided by the transcriptional action of glucocorticoids.
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PMID:Interaction between glucocorticoids and cyclic AMP in the regulation of phosphoenolpyruvate carboxykinase (GTP) in the isolated perfused rat liver. Effects of cordycepin and cycloheximide. 18 61

The administration of N6, O2'-dibutyryl cyclic AMP and theophylline to fasted-refed rats produces an 8-fold stimulation of the relative rate of hepatic phosphoenolpyruvate carboxykinase synthesis in 90 min, as measured by isotopic immunochemical techniques in vivo. The mechanism of this induction was studied first by using a homologous, noninitiating cell-free protein-synthesizing system derived from the liver of fasted-refed, cyclic AMP-treated rats. In such a system, a 5-fold increase in phosphoenolpyruvate carboxykinase synthseis is observed at 20 min post-treatment and a 9-fold stimulation at 75 min, indicating a rapid increase in the number of ribosomes engaged in the translation of the enzyme mRNA after exposure to cyclic AMP. The level of functional mRNA coding for phosphoenolpyruvate carboxykinase was then assayed in a wheat germ protein-synthesizing system capable of using rat liver mRNA as template. The template activity for phosphoenolpyruvate carboxykinase synthesis is greatly increased in the poly(A)-containing RNA isolated from cyclic AMP-induced animals. Both the increase in the capacity of the liver extract for in vitro phosphoenolpyruvate carboxykinase synthesis and the emergence of enzyme mRNA detected in the wheat germ assay are completely prevented by a pretreatment with cordycepin at doses which inhibit the appearance in the cytoplasm of newly synthesized poly(A)-containing RNA. These data demonstrate that the induction of hepatic phosphoenolpyruvate carboxykinase by cyclic AMP is characterized by the rapid build-up of newly synthesized, actively translated mRNA coding for the enzyme. The messenger accumulation could be due to an increase in the rate of its production or a decrease in the rate of its degradation.
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PMID:Increase in level of functional messenger RNA coding for phosphoenolpyruvate carboxykinase (GTP) during induction by cyclic adenosine 3':5'-monophosphate. 18 22

The effect of re-feeding glucose, protein or fat and the effect of insulin injection on the activity of hepatic phosphoenolpyruvate carboxykinase (GTP: oxaloacetate carboxy-lyase (transphosphorylating) EC 4.1.1.32), the concentration of hepatic cyclic AMP and the level of serum insulin was investigated in starved rats. Under all conditions examined the concentration of serum insulin was elevated to a high degree. However, only rats re-fed with glucose responded to the increase in serum insulin with a decrease in PEP carboxykinase activity, while the activity of the enzyme remained unchanged or was elevated after re-feeding protein or fat or after insulin injection, respectively. Since under all conditions there was a close correlation between cyclic AMP concentration and PEP carboxykinase activity, but not between the insulin level and enzyme activity, it is concluded that the hormone physiologically regulates PEP carboxykinase activity by decreasing the intrahepatic cyclic AMP concentration rather than by the postulated cyclic AMP-independent inhibition of specific mRNA translation.
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PMID:Physiological regulation of rat liver phosphoenolpyruvate carboxykinase (GTP) by insulin. Insignificance of a cyclic AMP-independent mechanism. 19 43

1. Measurements of pyruvate carboxylase, mitochondrial phosphoenolpyruvate carboxykinase (GTP), hexose bisphosphatase and glucose 6-phosphatase in developing sheep liver showed substantial activities of all enzymes in the foetus, especially towards the end of gestation. Cytosol phosphoenolpyruvate carboxykinase (GTP) in livers of mid-term foetuses was only 10% of the activity at birth. 2. All enzymes except pyruvate carboxylase showed 1.5-2-fold increases after birth. 3. Gluconeogenesis form [14C]actate could not be detected in chronically cannulated sheep foetuses at any developmental stage and was not initiated by the infusion of adrenaline or glucagon. 4. An active pathway of gluconeogenesis was evident in vivo within 2 min after natural birth or within 4 min after Caesarian delivery of term lambs, and was delayed in prematurely delivered lambs until breathing was established and the blood fully oxygenated. 5. It is proposed that oxygen availability initiates gluconeogenesis in the newborn lamb.
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PMID:The appearance of gluconeogenesis at birth in sheep. Activation of the pathway associated with blood oxygenation. 19 81

Circadian rhythms of alterations in content of 11-hydroxycorticosteroids and glucose in blood as well as in the activity of phosphoenolpyruvate carboxykinase, fructose-1,6-diphosphatase and glucose-6-phosphatase in liver and kidney tissues were studied under normal and inverted luminous regimens in summer and winter seasons. These patterns were distinctly altered depending on circadian rhythms in the above-mentioned conditions. The maximal content of 11-hydroxycorticosteroids in blood did not correlate with the highest activity of the gluconeogenesis key enzymes in the periods studied. Daily alterations in the activity of phosphoemolpyruvate carboxykinase were shown to be similar to that of the fructose-1,6-diphosphatase in various tissues at different seasons. But glucose-6-phosphatase differed distinctly from these enzymes by the daily rhythm of activity. This suggests that glucose-6-phosphatase has the other mechanism for regulation of its daily rhythm.
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PMID:[Use of circadian rhythms for analysis of the interrelationships between the concentration of glucocorticoids in the blood and the activity of key enzymes for gluconeogenesis in the liver and kidney of rats]. 19 7

The subcellular location of hexose diphosphatase, phosphoenolpyruvate carboxykinase and pyruvate carboxylase in baker's yeast (Saccharomyces cerevisiae) was investigated by density gradient centrifugation of spheroplast lysates obtained by osmotic shock treatment of spheroplasts and centrifugation for 10000 g x min. On the evidence obtained from zonal separations these three enzymes of gluconeogenesis are most probably located in the soluble cytosol.
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PMID:Location of three key enzymes of gluconeogenesis in baker's yeast. 19 63


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