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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. The effect of aeration on the key enzymes of gluconeogenesis was studied in baker's yeast (Saccharomyces cerevisiae) and in a nonrespiratory variant of S. cerevisiae grown under glucose limitation. 2. In baker's yeast phosphoenolpyruvate carboxykinase, hexosediphophatase and isocitrate lyase were completely repressed under anaerobic conditions. Their repression could be partially reversed by using intense aeration. 3. In the nonrespiratory variant these enzymes were absent independently of aeration. 4. Pyruvate carboxylase of baker's yeast showed maximal activity under anaerobic conditions. In the nonrespiratory variant pyruvate carboxylase had low activity under both anaerobic and aerobic conditions.
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PMID:Effect of aeration on the activity of gluconeogenetic enzymes in Saccharomyces cerevisiae growing under glucose limitation. 17 48

Two children are described who suffered from hypoglycemia and liver impairment. Assays of gluconeogenic enzymes in liver samples taken immediately after death demonstrated a deficiency of phosphoenolpyruvate carboxykinase, a key enzyme of gluconeogenesis. Post mortem examination demonstrated massive fat deposition in liver and kidney and to a lesser extent in other tissues. The fatty changes in liver and kidney could be explained by the absence of phosphoenolpyruvate carboxykinase, which would cause an alteration in the mitochondrial-cytosolic processes related to gluconeogenesis.
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PMID:Two cases of phosphoenolpyruvate carboxykinase deficiency. 17 67

The effect of injections of hormones in utero on fetal rat kidney and liver extramitochondrial phosphoenolpyruvate carboxykinase activity has been studied. Glucagon and thyroxine induced the liber enzyme but none of the hormones tested affected the renal enzyme. In the postnatal rat, the hepatic phosphoenolpyruvate barboxykinase activity is increased after triamcinolone or thyroxine injection but only triamcinolone injection increases the activity of the kidney enzyme. It is suggested that the rise in renal phosphoenolpyruvate carboxykinase activity at about 10 days of age is due to the increase in blood corticosterone content occurring at the same age.
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PMID:Hormonal control of renal phosphoenolpyruvate carboxykinase activity during development of the rat. 17 77

A deficiency of extramitochondrial form of hepatic phosphoenolpyruvate carboxykinase has been demonstrated in a boy with severe, persistent neonatal hypoglycaemia. Hepatic glucose-6-phosphatase, fructose-1.6-diphosphatase and pyruvate carboxylase were normal. The total activity of phosphoenolpyruvate carboxykinase was also normal, but the enzyme showed an abnormal subcellular distribution, virtually no activity being detected in the extramitochondrial fraction of a liver homogenate. The boy died at the age of 2 years 10 months. Autopsy revealed severe cerebral atrophy, atrophy of the optic nerve, and fatty infiltration of liver and kidney.
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PMID:Gluconeogenesis in infancy and childhood. III. Deficiency of the extramitochondrial form of hepatic phosphoenolpyruvate carboxykinase in a case of persistent neonatal hypoglycaemia. 17 69

The activities of key gluconeogenic enzymes in the liver of newborn guinea pigs delivered vaginally at term were monitored as a function of time following birth. The activities of glucose-6-phosphatase and fructose-1,6-diphosphatase did not show a significant increase over the first 72 h of life, neither did the activity of mitochondrial phosphoenolpyruvate carboxykinase. The mitochondrial enzyme pyruvate carboxylase and the cytosolic phosphoenolpyruvate carboxykinase (PEPCK) both increased significantly in the first 24 h postpartum. Mitochondrial protein and succinate dehydrogenase activities showed only slight increases in the 72-hour period. Rapid depletion of liver glycogen was evident in these animals following birth, but severe hypoglycaemia was not evident. Mitochondrial and cytosolic PEPCK showed similar kinetic behaviour with respect to their affinities for oxalacetate and divalent metal cation Mn++, though the mitochondrial enzyme would accept Mg++ as the divalent metal in place of Mn++. The role of the compartmented PEPCK activities is discussed.
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PMID:Development of gluconeogenic enzymes in the newborn guinea pig. 17 23

Reuber H35 cells were pulse-labeled with radioactive leucine and the influence of hormones, serum, and amino acids on protein degradation was investigated during a subsequent chase period. Radioactive, immunoprecipitable phosphoenolpyruvate carboxykinase (GTP) (EC 4.1.1.32) had a half-life of 5 to 6 hours which was not influenced by either N6, O2-dibutyryl adenosine 3':5'-monophosphate, dexamethasone, or insulin. The rate of phosphoenolpyruvate carboxykinase degradation was the same under steady state conditions as during the approach to a new steady state following hormonal induction or deinduction of the enzyme. Therefore, hormonal regulation of enzyme activity in vivo is the result of changes in the rate of enzyme synthesis. The rate of proteolysis for total cell proteins was increased under nutritional step-down conditions produced by the removal of serum or amino acids, or both, from the medium. This effect was completely prevented by insulin. Cycloheximide and puromycin, but not actinomycin D or cordycepin, inhibited protein degradation under step-down conditions but did not further decrease the basal rate of proteolysis measured in the presence of either insulin or serum plus amino acids. There was a good correlation between changes in proteolysis produced by serum and amino acids and changes in the degradation rate of phosphoenolpyruvate carboxykinase. Also, inhibition of proteolysis with cycloheximide and puromycin was accompanied by a decrease in the degradation rate for enzyme antigen. It is suggested that nutritional step-down leads either to the synthesis or activation of a proteolytic system.
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PMID:Infulence of hormones and medium composition on the degradation of phosphoenolpyruvate carboxykinase (GTP) and total protein in Reuber H35 cells. 18 1

The effect of starvation on the activity of hepatic phosphoenolpyruvate carboxykinase (GTP:oxaloacetate carboxy-lyase (transphosphorylating), EC 4.1.1.32), and on the response of the enzyme to N6-O2'dibutyryl adenosine 3', 5'-monophosphate was investigated in intact and glucocorticoid-deprived rats. In the liver of intact animals, starvation produced a rapid increase in the concentration of cyclic AMP and a corresponding increase in the activity of phosphoenolpyruvate carboxykinase. The kinetics of both changes were not affected by adrenalectomy. Injection of N6-O2'-dibutyryl adenosine 3', 5'-monophosphate into intact starved rats resulted in an immediate, dramatic increase in phosphoenolpyruvate carboxykinase activity above the starvation level. Adrenalectomy completely blocked the response of the enzyme to the cyclic nucleotide. Restoration of hydrocortisone to the adrenalectomized animals restored the full N6-I2'dibutyryl adenosine 3', 5'-monophosphate effect after a lag period of 2 h. The physiological significance of these findings is considered. The data are interpreted with regard to the current hypothesis that glucocorticoids promote an increase in translatable phosphoenolpyruvate carboxykinase mRNA, while cyclic AMP enhances the translation of preexisting specific mRNA templates.
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PMID:Induction of rat liver phosphoenolpyruvate carbonxykinase (GTP) by cyclic AMP during starvation. The permissive action of glucocorticoids. 18 Oct 80

The existence of a glyconeogenic pathway in rat skin has been demonstrated by measurement of three of the key glyconeogenic enzymes, fructose 1,6-bisphosphatase, pyruvate carboxylase and phosphoenolpyruvate carboxykinase, and by studies on the incorporation in vitro of carbon from pyruvate and alanine into skin glycogen.
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PMID:The existence of a glyconeogenic pathway in rat skin. 18 51

The activities of key gluconeogenic enzymes in the livers of newborn guinea pigs were monitored as a function of time following birth either vaginally at term or prematurely by cesarian section at 62 days of gestation. The activity of hepatic glucose-6-phosphatase rose dramatically from 1.40 +/- 0.26 mumol/min/g at birth to a maximum of 6.8 +/- 0.9 mumol/min/g at 24 hr in prematurely delivered animals although there was little significant change in activity in full term animals. The activity of hepatic fructose-1,6-diphosphatase and mitochondrial phosphoenolpyruvate carboxykinase changed little over the first 3 days of life in either full term or premature animals. Cytosolic phosphoenolpyruvate carboxykinase, on the other hand, had low activity at birth being 0.11 +/- 0.03 mumol/min/g in full term and 0.06 +/- 0.04 mumol in premature animals rising to values of 0.71 +/- 0.06 and 1.12 +/- 0.12 mumol/min/g, respectively, at 24 hr of life. Pyruvate carboxylase activities in the premature animals remained significantly lower than those in full term animals in the first 72 hr of life. Transient hypoglycemia was evident in the prematurely delivered animals, but not in the full term animals, the blood glucose values being 82 +/- 7 mg/100 ml for the full term animals and 20 +/- 8 mg/100 ml for the premature infants at 2 hr of life.
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PMID:The effect of premature delivery on the development of gluconeogenic enzymes in the guinea pig. 18 25

The effect of cold exposure (5 degrees C) on the concentration of cyclic AMP and on the activity of phosphoenolpyruvate carboxykinase (GTP: oxaloacetate carboxy-lyase (transphosphorylating), EC 4.1.1.32) was investigated in the liver of intact and adrenalectomized starved rats. Intact starved rats responded to cold exposure with a large increase in both the concentration of hepatic cyclic AMP and the activity of phosphoenolpyruvate carboxykinase above the starvation level. Adrenalectomy did not impair the cold-induced maximum elevation of cyclic AMP but totally prevented the response of the enzyme to cold. Yet, this response was completely restored by hydrocortisone treatment, while the steroid per se had no effect on enzyme activity. In isolated perfused livers of intact starved rats dibutyryl cyclic AMP provoked an immediate dramatic increase in phosphoenolpyruvate carboxykinase activity above the starvation level even if mRNA synthesis was inhibited by cordycepin. However, cyclic AMP was ineffective in increasing enzyme activity in livers of adrenalectomized rats. From these results it is suggested (i) that in starved rats the adaptation to the enhanced glucose demand provoked by cold exposure includes the induction of hepatic phosphoenolpyruvate carboxykinase above the starvation level, (ii) that this induction is due to the cold-induced increase in hepatic cyclic AMP levels, (iii) that cyclic AMP stimulates enzyme synthesis at a post-transcriptional step and (iv) that the cold-induced cyclic AMP-mediated induction of phosphoenolpyruvate carboxykinase above the starvation level requires the "permissive" effect of glucocorticoids.
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PMID:Effect of cold exposure on phosphoenolpyruvate carboxykinase (GTP) activity and cyclic amp concentration in livers of starved rats. Role of glucorticoids. 18 3


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