The development of pyruvate kinase, glycerol kinase and phosphoenolpyruvate carboxykinase activities in liver and adipose tissue of the rat

1968 ◽  
Vol 24 (5) ◽  
pp. 428-429 ◽  
Author(s):  
Ph. Hahn ◽  
R. Greenberg
Keyword(s):  
Adipose Tissue ◽  
Pyruvate Kinase ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Glycerol Kinase

scholarly journals Properties of pyruvate kinase and phosphoenolpyruvate carboxykinase in relation to the direction and regulation of phosphoenolpyruvate metabolism in muscles of the frog and marine invertebrates

1978 ◽  
Vol 174 (3) ◽  
pp. 979-987 ◽  
Author(s):  
Victor A. Zammit ◽  
Eric A. Newsholme
Keyword(s):  
Pyruvate Kinase ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Marine Invertebrates ◽  
Adductor Muscle ◽  
Sea Anemone ◽  
Anaerobic Conditions ◽  
Fructose Bisphosphate ◽  
Low Concentrations ◽  
Optimum Ph ◽  
Hill Coefficients

1. The properties of pyruvate kinase and, if present, phosphoenolpyruvate carboxykinase from the muscles of the sea anemone, scallop, oyster, crab, lobster and frog were investigated. 2. In general, the properties of pyruvate kinase from all muscles were similar, except for those of the enzyme from the oyster (adductor muscle); the pH optima were between 7.1 and 7.4, whereas that for oyster was 8.2; fructose bisphosphate lowered the optimum pH of the oyster enzyme from 8.2 to 7.1, but it had no effect on the enzymes from other muscles. Hill coefficients for the effect of the concentration of phosphoenolpyruvate were close to unity in the absence of added alanine for the enzymes from all muscles except oyster adductor muscle; it was 1.5 for this enzyme. Alanine inhibited the enzyme from all muscles except the frog; this inhibition was relieved by fructose bisphosphate. Low concentrations of alanine were very effective with the enzyme from the oyster (50% inhibition was observed at 0.4mm). Fructose bisphosphate activated the enzyme from all muscles, but extremely low concentrations were effective with the oyster enzyme (0.13μm produced 50% activation). 3. In general, the properties of phosphoenolpyruvate carboxykinase from the sea anemone and oyster muscles are similar: the Km values for phosphoenolpyruvate are low (0.10 and 0.13mm); the enzymes require Mn2+ in addition to Mg2+ for activity; and ITP inhibits the enzymes and the inhibition is relieved by alanine. These latter compounds had no effect on enzymes from other muscles. 4. It is suggested that changes in concentrations of fructose bisphosphate, alanine and ITP produce a coordinated mechanism of control of the activities of pyruvate kinase and phosphoenolpyruvate carboxykinase in the sea anemone and oyster muscles, which ensures that phosphoenolpyruvate is converted into oxaloacetate and then into succinate in these muscles under anaerobic conditions. 5. It is suggested that in the muscles of the crab, lobster and frog, phosphoenolpyruvate carboxykinase catalyses the conversion of oxaloacetate into phosphoenolpyruvate. This may be part of a pathway for the oxidation of some amino acids in these muscles.

Carbohydrate metabolism by primary cultures of rabbit proximal tubules

1989 ◽  
Vol 256 (3) ◽  
pp. C532-C539 ◽  
Author(s):  
M. J. Tang ◽  
K. R. Suresh ◽  
R. L. Tannen
Keyword(s):  
Pyruvate Kinase ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Cultured Cells ◽  
Primary Cultures ◽  
Lactate Production ◽  
Proximal Tubules ◽  
Glycolytic Metabolism ◽  
Proximal Tubular Cells ◽  
Tubular Cells ◽  
Proximal Tubular

Renal proximal tubular epithelia were used to assess the factors responsible for the induction of glycolysis in cultured cells. Primary cultures of rabbit proximal tubules, which achieved confluency at 6 days, exhibited hormonal responsiveness and brush-border characteristics typical of proximal tubular cells. Beginning at day 4, these cultured cells exhibited increased glycolytic metabolism reflected by enhanced glucose uptake and lactate production, along with parallel increases in activity of the glycolytic enzymes, pyruvate kinase and lactate dehydrogenase. The gluconeogenic enzymes, phosphoenolpyruvate carboxykinase (PEPCK) and fructose-1,6-bisphosphatase (FDP), were downregulated, and the cultured cells exhibited lower oxygen consumption rates than fresh tubules. Cells grown on a rocker, to mitigate hypoxia, exhibited a metabolic and enzymatic profile similar to cells grown under still conditions. ATP levels in cultured cells were higher than in fresh tubules. Furthermore, pyruvate kinase activity was higher in cells grown in media containing 0.5 as contrasted with 25 mM glucose. The enhanced glycolytic metabolism exhibited by cultured proximal tubular cells appears to be a characteristic of proliferation and is not a response to hypoxia, the Pasteur effect, or environmental glucose.

scholarly journals Metabolic Effects of Oral Phenelzine Treatment on High-Sucrose-Drinking Mice

2018 ◽  
Vol 19 (10) ◽  
pp. 2904 ◽  
Author(s):  
Christian Carpéné ◽  
Saioa Gómez-Zorita ◽  
Alice Chaplin ◽  
Josep Mercader
Keyword(s):  
Adipose Tissue ◽  
Phosphoenolpyruvate Carboxykinase ◽  
De Novo ◽  
Uncoupling Protein ◽  
De Novo Lipogenesis ◽  
Metabolic Effects ◽  
Mrna Levels ◽  
Brown Adipose ◽  
High Sucrose ◽  
Sucrose Drinking

Phenelzine has been suggested to have an antiobesity effect by inhibiting de novo lipogenesis, which led us to investigate the metabolic effects of oral chronic phenelzine treatment in high-sucrose-drinking mice. Sucrose-drinking mice presented higher body weight gain and adiposity versus controls. Phenelzine addition did not decrease such parameters, even though fat pad lipid content and weights were not different from controls. In visceral adipocytes, phenelzine did not impair insulin-stimulated de novo lipogenesis and had no effect on lipolysis. However, phenelzine reduced the mRNA levels of glucose transporters 1 and 4 and phosphoenolpyruvate carboxykinase in inguinal white adipose tissue (iWAT), and altered circulating levels of free fatty acids (FFA) and glycerol. Interestingly, glycemia was restored in phenelzine-treated mice, which also had higher insulinaemia. Phenelzine-treated mice presented higher rectal temperature, which was associated to reduced mRNA levels of uncoupling protein 1 in brown adipose tissue. Furthermore, unlike sucrose-drinking mice, hepatic malondialdehyde levels were not altered. In conclusion, although de novo lipogenesis was not inhibited by phenelzine, the data suggest that the ability to re-esterify FFA is impaired in iWAT. Moreover, the effects on glucose homeostasis and oxidative stress suggest that phenelzine could alleviate obesity-related alterations and deserves further investigation in obesity models.

Glucocorticoids and regulation of phosphoenolpyruvate carboxykinase activity in rat brown adipose tissue.

1978 ◽  
Vol 235 (2) ◽  
pp. E197
Author(s):  
D Feldman ◽  
M Hirst
Keyword(s):  
Adipose Tissue ◽  
Brown Adipose Tissue ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Base Line ◽  
Glucocorticoid Treatment ◽  
Low Carbohydrate Diet ◽  
Low Fat Diet ◽  
Brown Adipose ◽  
Low Carbohydrate ◽  
Reduced Activity

Studied were performed to examine the factors that might regulate phosphoenolpyruvate carboxykinase (PEPCK) activity in rat brown adipose tissue (BAT) and to determine the role played by glucocorticoids in regulating this enzyme. Comparison was made to white adipose tissue (WAT) where PEPCK activity is known to be glucocorticoid regulated. PEPCK activity in BAT did not respond to adrenalectomy or dexamethasone, whereas WAT activity was increased and decreased, respectively, by these maneuvers. Three conditions were found in which BAT PEPCK activity was stimulated: 1) fasting, 2) feeding a high-fat/low-carbohydrate diet, and 3) during the neonatal period. In each case glucocorticoid treatment prevented the stimulation in PEPCK activity and restored the enzyme to base-line levels. In conditions 1 and 2, enzyme activity was also stimulated in WAT, but in contradistinction to BAT, glucocorticoid administration reduced activity to low levels significantly below base-line activity. Two conditions were found which suppressed PEPCK activity in BAT: exposure to a cold environment and feeding a high-protein/low-fat diet. WAT PEPCK was unaltered by exposure to cold. Thus, differences in PEPCK regulation between BAT and WAT were demonstrated, and the response to glucocorticoids was unique in BAT.

Fatty acid recycling in adipocytes: a role for glyceroneogenesis and phosphoenolpyruvate carboxykinase

2003 ◽  
Vol 31 (6) ◽  
pp. 1125-1129 ◽  
Author(s):  
C. Forest ◽  
J. Tordjman ◽  
M. Glorian ◽  
E. Duplus ◽  
G. Chauvet ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Amino Acids ◽  
Adipose Tissue ◽  
Fatty Acid ◽  
White Adipose Tissue ◽  
Metabolic Pathway ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Important Pathway ◽  
Low Activity

FA (fatty acid) recycling in adipose tissue appears to be an important pathway for regulating FA release into the blood during fasting. Re-esterification requires G3P (glycerol 3-phosphate), which cannot be synthesized from glucose because glycolysis is much reduced under such circumstances. In addition, G3P can scarcely originate from glycerol since glycerol kinase has a very low activity in white adipose tissue. It was shown about 35 years ago that a metabolic pathway named glyceroneogenesis, which allows G3P synthesis from non-carbohydrate precursors like pyruvate, lactate or amino acids, is activated during fasting. The major enzyme in this pathway was shown to be PEPCK-C [cytosolic phosphoenolpyruvate carboxykinase (GTP); EC 4.1.1.32]. The present review analyses the mechanisms by which a series of hormones and nutrients affect PEPCK-C gene transcription and glyceroneogenesis and describes evidence for dysregulation of this pathway in type 2 diabetes.

Effect of 6-hydroxydopamine and α-methyltyrosine on brown adipose tissue of infant rats

1977 ◽  
Vol 55 (2) ◽  
pp. 272-278 ◽  
Author(s):  
Josef P. Skala ◽  
Peter Hahn
Keyword(s):  
Adipose Tissue ◽  
Brown Adipose Tissue ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Fatty Acid Synthetase ◽  
Total Protein Content ◽  
Infant Rats ◽  
Brown Adipose ◽  
6 Hydroxydopamine ◽  
Increased Activity

A single-dose administration of 6-hydroxydopamine (50 mg/kg body weight, sc) to infant rats resulted in an enlargement, higher fresh weight, markedly elevated lipid content, and higher total protein content of their interscapular and cervical brown adipose tissue. The protein kinase (EC 2.7.1.37) activation ratio in the tissue was decreased as was the phosphoenolpyruvate carboxykinase (EC 4.1.1.32) activity. Fatty acid synthetase, on the other hand, showed an increased activity. These changes commenced as soon as 24 h after the administration of the drug, were fully developed 2–4 days later, and persisted for at least 14 days. The results are in line with the assumption that 6-hydroxydopamine administration causes chemical sympathectomy of brown adipose tissue. This is further supported by the fact that treatment with α-methyltyrosine, which is known to competitively inhibit norepinephrine synthesis, results in similar changes in brown fat of infant rats. Hence it seems that 6-hydroxydopamine administration offers a simple and inexpensive experimental model for studies of the role of the norepinephrine-mediated sympathetic nervous system in brown adipose tissue function and development.

Regulation of phosphoenolpyruvate carboxykinase and pyruvate kinase in Saccharomyces cerevisiae grown in the presence of glycolytic and gluconeogenic carbon sources and the role of mitochondrial function on gluconeogenesis

1986 ◽  
Vol 32 (12) ◽  
pp. 969-972 ◽  
Author(s):  
Albert J. Wilson ◽  
J. K. Bhattacharjee
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Pyruvate Kinase ◽  
Growth Medium ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Carbon Sources ◽  
Absolute Requirement ◽  
Fructose 1,6 Bisphosphatase ◽  
Futile Cycling ◽  
Respiratory Deficient

Phosphoenolpyruvate carboxykinase (PEPCKase) and pyruvate kinase (PKase) were measured in Saccharomyces cerevisiae grown in the presence of glycolytic and gluconeogenic carbon sources. The PEPCKase activity was highest in ethanol-grown cells. However, high PEPCKase activity was also observed in cells grown in 1% glucose, especially as compared with the activity of sucrose-, maltose-, or galactose-grown cells. Activity was first detected after 12 h when glucose was exhausted from the growth medium. The PKase activity was very high in glucose-grown cells; considerable activity was also present in ethanol- and pyruvate-grown cells. The absolute requirement of respiration for gluconeogenesis was demonstrated by the absence or significantly low levels of PEPCKase and fructose-1,6-bisphosphatase activities observed in respiratory deficient mutants, as well as in wild-type S. cerevisiae cells grown in the presence of glucose and antimycin A or chloramphenicol. Obligate glycolytic and gluconeogenic enzymes were present sumultaneously only in stationary phase cells, but not in exponential phase cells; hence futile cycling could not occur in log phase cells regardless of the presence of carbon source in the growth medium.

In vivo effect of Trigonella foenum graecum on the expression of pyruvate kinase, phosphoenolpyruvate carboxykinase, and distribution of glucose transporter (GLUT4) in alloxan-diabetic rats

2006 ◽  
Vol 84 (6) ◽  
pp. 647-654 ◽  
Author(s):  
Sameer Mohammad ◽  
Asia Taha ◽  
Kamal Akhtar ◽  
R.N.K. Bamezai ◽  
Najma Zaheer Baquer
Keyword(s):  
Skeletal Muscle ◽  
Pyruvate Kinase ◽  
Plasma Glucose ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Glucose Transporter ◽  
Diabetic Rats ◽  
Altered Expression ◽  
Glucose Levels ◽  
Glucose Transporter Glut4

Plasma glucose levels are maintained by a precise balance between glucose production and its use. Liver pyruvate kinase (PK) and phosphoenolpyruvate carboxykinase (PEPCK), 2 key enzymes of glycolysis and gluconeogenesis, respectively, play a crucial role in this glucose homeostasis along with skeletal muscle glucose transporter (GLUT4). In the diabetic state, this balance is disturbed owing to the absence of insulin, the principal factor controlling this regulation. In the present study, alloxan-diabetic animals having high glucose levels of more than 300 mmol/L have been taken and the administration of Trigonella seed powder (TSP) to the diabetic animals was assessed for its effect on the expression of PK and PEPCK in liver and GLUT4 distribution in skeletal muscle of alloxan-diabetic rats. TSP treatment to the diabetic animals resulted in a marked decrease in the plasma glucose levels. Trigonella treatment partially restored the altered expression of PK and PEPCK. TSP treatment also corrected the alterations in the distribution of GLUT4 in the skeletal muscle.

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