Regulation by Phosphoenolpyruvate of Fructose-1,6-diphosphatase in Skeletal Muscle: Evidence for an Allosteric Activator of the Enzyme

1972 ◽  
Vol 50 (6) ◽  
pp. 710-713 ◽  
Author(s):  
Hans W. Behrisch
Keyword(s):  
Skeletal Muscle ◽  
Low Temperature ◽  
High Temperatures ◽  
Pyruvate Carboxylase ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Cold Water ◽  
Gluconeogenic Enzymes ◽  
Allosteric Inhibitor ◽  
Crustacean Muscle ◽  
Allosteric Activator

Fructose-1,6-diphosphatase (FDPase) from muscle of three cold-water crustaceans was found to be activated by phosphoenolpyruvate (PEP). PEP appears to reduce Km for FDP at low and high temperatures; however, at low temperature the effect on Km of FDP is amplified. In addition PEP reduces affinity of FDPase for AMP, the allosteric inhibitor of the enzyme. These results suggest a coupling of several of the regulatory steps in the glycolytic and gluconeogenic sequences. In addition, skeletal muscle of the crustaceans used in the present study contains substantial (higher than 500 μmol/h/g tissue) activities of the gluconeogenic enzymes phosphoenolpyruvate carboxykinase, pyruvate carboxylase, and glucose-6-phosphatase. On the basis of these results it is proposed that gluconeogenesis is a functioning pathway in crustacean muscle.

The enigmatic presence of all gluconeogenic enzymes in Schistosoma mansoni adults

Parasitology ◽  
1991 ◽  
Vol 102 (2) ◽  
pp. 267-276 ◽  
Author(s):  
A. G. M. Tielens ◽  
P. Van Der Meer ◽  
J. M. Van Den Heuvel ◽  
S. G. Van Den Bergh
Keyword(s):  
Skeletal Muscle ◽  
Schistosoma Mansoni ◽  
Rat Liver ◽  
Pyruvate Carboxylase ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Rat Skeletal Muscle ◽  
Gluconeogenic Enzymes ◽  
Muscle Tissues ◽  
Order Of Magnitude ◽  
C Nmr

SUMMARYThe activities of glucose-6-phosphatase (G6Pase), frucrose-1,6-bisphosphatase (FBPase), phosphoenolpyruvate carboxykinase (PEPCK) and pyruvate carboxylase (PC) were determined in homogenates of adult Schistosoma mansoni worms and compared with the activities in homogenates of rat liver and rat skeletal muscle, tissues with a high and a low gluconeogenic capacity, respectively. All four gluconeogenic enzymes were present in S. mansoni. The enzymes were less active than in rat liver, but the activities of G6Pase, PEPCK and PC were at least an order of magnitude higher than in rat skeletal muscle whereas FBPase was approximately equally active in S. mansoni and in rat muscle. Experiments with 14C-labelled substrates or [14C]NaHCO3 failed to demonstrate the actual occurrence of gluconeogenesis in S. mansoni. Some possible other functions of the gluconeogenic enzymes were investigated. Experiments with inhibitors of PEPCK gave no indications that this enzyme was involved in the degradation of glucose. This was confirmed by 13C-NMR experiments which indicated that lactate was formed from phosphoenolpyruvate via the actions of pyruvate kinase and lactate dehydrogenase, and that PEPCK did not participate in the formation of lactate. Substrate cycling between fructose-6-phosphate and fructose-1,6-bisphosphate was demonstrated to occur in adult S. mansoni. This shows that FBPase participates in the glucose metabolism of this parasite.

Activities of the enzymes of hepatic gluconeogenesis in periparturient dairy cows with induced fatty liver

2004 ◽  
Vol 71 (2) ◽  
pp. 129-134 ◽  
Author(s):  
Absolom Murondoti ◽  
Ruurd Jorritsma ◽  
Anton C Beynen ◽  
Theo Wensing ◽  
Math JH Geelen
Keyword(s):  
Fatty Liver ◽  
Dairy Cows ◽  
Pyruvate Carboxylase ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Post Partum ◽  
Sampling Period ◽  
Negative Energy ◽  
Hepatic Gluconeogenesis ◽  
Gluconeogenic Enzymes ◽  
Blood Glucose Concentrations

The objective was to measure the activities of all the enzymes essential for hepatic gluconeogenesis in dairy cows with induced fatty liver. We aimed to induce severe fatty liver in ten experimental cows by overfeeding them during the dry period while seven control cows were maintained on a restricted diet. To induce a marked negative energy balance, the experimental cows were deprived of feed for 8 h immediately after parturition. In addition, the experimental cows were given a restricted amount of diet during the first 5 d of lactation. Liver samples were collected 1 week before and 1, 2 and 4 weeks after parturition. Before parturition, liver triacylglycerol concentrations did not differ between the two groups. After parturition, the experimental cows developed marked fatty liver as indicated by a higher level of triacylglycerols in the liver compared with the control cows.Before parturition, all gluconeogenic enzymes in the liver were lower in experimental cows than in control cows. Phosphoenolpyruvate carboxykinase, pyruvate carboxylase and propionyl-CoA carboxylase were significantly lower and fructose 1,6-bisphosphatase and glucose 6-phosphatase tended to be lower in the experimental cows. The activities of two crucial enzymes for gluconeogenesis in ruminants, i.e., phosphoenolpyruvate carboxykinase and propionyl-CoA carboxylase, remained low throughout the sampling period post partum. Activities of pyruvate carboxylase and glucose 6-phosphatase in the experimental cows post partum were upgraded to values similar to those of the control cows. The results showed that the capacity for hepatic gluconeogenesis before parturition was lower in cows with induced fatty liver than in control cows. After parturition, the low activities of crucial gluconeogenic enzymes indicated insufficient production of glucose. It is suggested that the low gluconeogenic capacity leads successively to low blood glucose concentrations, low insulin levels and high rates of mobilization of fatty acid, causing severe hepatic lipidosis.

DDT-Induced Stimulation of Key Gluconeogenic Enzymes In Rat Kidney Cortex

1972 ◽  
Vol 50 (2) ◽  
pp. 225-229 ◽  
Author(s):  
S. Kacew ◽  
R. L. Singhal ◽  
G. M. Ling
Keyword(s):  
Pyruvate Carboxylase ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Rat Kidney ◽  
Kidney Cortex ◽  
Glucocorticoid Hormones ◽  
Rat Kidney Cortex ◽  
Gluconeogenic Enzymes ◽  
Maximal Stimulation ◽  
Adrenalectomized Rats ◽  
Stimulation Of

Administration of technical DDT or o,p′-DDT produced marked increases in pyruvate carboxylase, phosphoenolpyruvate carboxykinase, fructose-1,6-diphosphatase, and glueose-6-phospfaatase activities in rat kidney cortex. Significant increases in these key gluconeogenic enzymes occurred at 2–3 days and maximal stimulation was seen 5–7 days after the beginning of o,p′-DDT treatment. This DDT isomer, when given to adrenalectomized rats, produced increases in renal enzymes similar to those observed in intact animals. Furthermore, since administration of triamcinolone to o,p′-DDT-treated rats failed to potentiate the action of this insecticide on various enzymes, evidence indicates that the stimulation of kidney cortex gluconeogenesis by DDT is not mediated through a release of glucocorticoid hormones from the adrenal cortex.

A putative pathway of glyconeogenesis in skeletal muscle

1981 ◽  
Vol 1 (2) ◽  
pp. 157-165 ◽  
Author(s):  
Bhanu R. Odedra ◽  
T. Norman Palmer
Keyword(s):  
Skeletal Muscle ◽  
Malic Enzyme ◽  
Pyruvate Carboxylase ◽  
Phosphoenolpyruvate Carboxykinase ◽  
De Novo ◽  
Glycogen Biosynthesis ◽  
Glycogen Sparing ◽  
Specific Inhibitors

Evidence is presented in support of a pathway in skeletal muscle of glyconeogenesis (glycogen biosynthesis de novo) from L-glutamate and related amino acids involving the enzyme phosphoenolpyruvate carboxykinase (PEP CK). In the rat hemidiaphragm in vitro, not only did L-[U-14C]glutamate exert a glycogen-sparing action, but14C-label was incorporated into glycogen. The incorporation is thought not to be simply via label randomization and was decreased by factors that increased glycolysis or pyruvate oxidation. 3-Mercaptopicolinate and amino-oxyacetate, specific inhibitors of PEP CK and aminotransferase-type enzymes, respectively, decreased14C-incorporation from L-[U-14C]glutamate into glycogen. No quantitative determination of apparent glyconeogenic flux was made, and it remains to be established whether glyconeogenesis via PEP CK and/or via PEP CK coupled with 'malic' enzyme (or pyruvate carboxylase) is functionally important in skeletal muscle.

scholarly journals Lack of skeletal muscle IL-6 influences hepatic glucose metabolism in mice during prolonged exercise

2017 ◽  
Vol 312 (4) ◽  
pp. R626-R636 ◽  
Author(s):  
Lærke Bertholdt ◽  
Anders Gudiksen ◽  
Camilla L. Schwartz ◽  
Jakob G. Knudsen ◽  
Henriette Pilegaard
Keyword(s):  
Skeletal Muscle ◽  
Glucose Metabolism ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Prolonged Exercise ◽  
Hepatic Glycogen ◽  
Glucose Content ◽  
Hepatic Glucose Metabolism ◽  
Hepatic Glucose ◽  
Single Bout ◽  
Substrate Choice

The liver is essential in maintaining and regulating glucose homeostasis during prolonged exercise. IL-6 has been shown to be secreted from skeletal muscle during exercise and has been suggested to signal to the liver. Therefore, the aim of this study was to investigate the role of skeletal muscle IL-6 on hepatic glucose regulation and substrate choice during prolonged exercise. Skeletal muscle-specific IL-6 knockout (IL-6 MKO) mice (age, 12–14 wk) and littermate lox/lox (Control) mice were either rested (Rest) or completed a single bout of exercise for 10, 60, or 120 min, and the liver was quickly obtained. Hepatic IL-6 mRNA was higher at 60 min of exercise, and hepatic signal transducer and activator of transcription 3 was higher at 120 min of exercise than at rest in both genotypes. Hepatic glycogen was higher in IL-6 MKO mice than control mice at rest, but decreased similarly during exercise in the two genotypes, and hepatic glucose content was lower in IL-6 MKO than control mice at 120 min of exercise. Hepatic phosphoenolpyruvate carboxykinase mRNA and protein increased in both genotypes at 120 min of exercise, whereas hepatic glucose 6 phosphatase protein remained unchanged. Furthermore, IL-6 MKO mice had higher hepatic pyruvate dehydrogenase (PDH)Ser232 and PDHSer300 phosphorylation than control mice at rest. In conclusion, hepatic gluconeogenic capacity in mice is increased during prolonged exercise independent of muscle IL-6. Furthermore, Skeletal muscle IL-6 influences hepatic substrate regulation at rest and hepatic glucose metabolism during prolonged exercise, seemingly independent of IL-6 signaling in the liver.

scholarly journals Preventing thermoinhibition in a thermosensitive lettuce genotype by seed imbibition at low temperature

2003 ◽  
Vol 60 (3) ◽  
pp. 477-480 ◽  
Author(s):  
Warley Marcos Nascimento
Keyword(s):  
Seed Germination ◽  
Low Temperature ◽  
High Temperatures ◽  
Lactuca Sativa ◽  
Lettuce Seed ◽  
Temperature Dependent ◽  
Lettuce Seeds ◽  
Lactuca Sativa L ◽  
Lettuce Seed Germination ◽  
Dark Green

Lettuce (Lactuca sativa L.) seed germination is strongly temperature dependent and under high temperatures, germination of most of genotypes can be erratic or completely inhibited. Lettuce seeds of 'Dark Green Boston' (DGB) were incubated at temperatures ranging from 15° to 35°C at light and dark conditions. Other seeds were imbibed in dark at 20°; 25°; 30°; and 35°C for 8 and 16 hours and then transferred to 20 or 35°C, in dark. Seeds were also incubated at constant temperature of 20° and 35 °C, in the dark, as control. In another treatment, seeds were primed for 3 days at 15°C with constant light. DGB lettuce seeds required light to germinate adequately at temperatures above 25°C. Seeds incubated at 20°C had 97% germination, whereas seeds incubated at 35°C did not germinate. Seeds imbibed at 20°C for 8 and 16 hours had germination. At 35°C, seeds imbibed initially at 20°C for 8 and 16 hours, had 89 and 97% germination, respectively. Seeds imbibed at 25°C for 16 hours, germinated satisfactory at 35°C. High temperatures of imbibition led to no germination. Primed and non-primed seeds had 100% germination at 20°C. Primed seeds had 100% germination at 35°C, whereas non-primed seeds germinate only 4%. The first hours of imbibition are very critical for lettuce seed germination at high temperatures.

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