scholarly journals Fructose 2,6-bisphosphate and its phosphorothioate analogue. Comparison of their hydrolysis and action on glycolytic and gluconeogenic enzymes

1988 ◽  
Vol 253 (2) ◽  
pp. 597-601 ◽  
Author(s):  
M H Rider ◽  
D A Kuntz ◽  
L Hue
Keyword(s):  
Pyruvate Kinase ◽  
Chicken Liver ◽  
Gluconeogenic Enzymes ◽  
Fructose 2 ◽  
Fructose 1,6 Bisphosphatase ◽  
Enzyme Intermediate

Purified chicken liver 6-phosphofructo-2-kinase/fructose 2,6-bisphosphatase was phosphorylated either from fructose 2,6-bis[2-32P]phosphate or fructose 2-phosphoro[35S]thioate 6-phosphate. The turnover of the thiophosphorylated enzyme intermediate as well as the overall phosphatase reaction was four times faster than with authentic fructose 2,6-bisphosphate. Fructose 2-phosphorothioate 6-phosphate was 10-100-fold less potent than authentic fructose 2,6-bisphosphate in stimulating 6-phosphofructo-1-kinase and pyrophosphate:fructose 6-phosphate phosphotransferase, but about 10 times more potent in inhibiting fructose 1,6-bisphosphatase. The analogue was twice as effective as authentic fructose 2,6-bisphosphate in stimulating pyruvate kinase from trypanosomes.

Light-Dependent Sucrose Synthesis in Cell-Free (Reconstituted) Lysates of Evacuolated Mesophyll Protoplasts

1990 ◽  
Vol 45 (3-4) ◽  
pp. 217-222 ◽  
Author(s):  
Manfred Steingraber ◽  
Hanns Frohnmeyer ◽  
Rüdiger Hampp
Keyword(s):  
Percoll Gradient ◽  
Functional Interaction ◽  
Free System ◽  
Mesophyll Protoplasts ◽  
Cell Free System ◽  
Fructose 2 ◽  
Fructose 1,6 Bisphosphatase ◽  
Reconstituted System ◽  
Oil Filtration

Abstract Oat mesophyll protoplasts were evacuolated by centrifugation on a Percoll gradient and used as starting material for establishing a functional cell-free system. For this purpose evacuolated protoplasts were osmotically lysed. From the resulting homogenate a cytosolic fraction was obtained by silicon oil filtration. This fraction was used to dilute preparations of lysed evacu­olated protoplasts in order to reduce the number of organelles per volume cytosol. The latter was necessary to increase light-dependent oxygen evolution of the cell-free system. The result­ing kind of “reconstituted” system showed light-dependent sucrose formation (about 100 nmol (mg Chi)-1 · hr-1) with bicarbonate as the only substrate. As this property depends on a functional interaction of chloroplast and cytosolic reactions, this cell-free system appeared to perform essential steps of partitioning of CO2 between starch and sucrose. Addition of about 12 μm fructose 2 ,6 -bisphosphate, an inhibitor of fructose 1,6 -bisphosphatase and an activator of the PPi-dependent fructose 6 -phosphate phosphotransferase, caused sucrose degradation in the light. Thus, this cell-free system allows both the study of cytosolic enzyme activities under quasi in vivo conditions and the manipulation of cellular reaction sequences by plasma mem­brane-impermeable compounds.

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.

scholarly journals Activation of chicken liver fructose-1,6-bisphosphatase by oxidized glutathione

FEBS Letters ◽  
1986 ◽  
Vol 200 (2) ◽  
pp. 347-351 ◽  
Author(s):  
Peter Han ◽  
David Hang ◽  
Nerimiah Emmett ◽  
Grace Han ◽  
Joe Johnson
Keyword(s):  
Chicken Liver ◽  
Oxidized Glutathione ◽  
Fructose 1,6 Bisphosphatase

scholarly journals Metabolic control of hepatic gluconeogenesis during exercise

1983 ◽  
Vol 212 (3) ◽  
pp. 633-639 ◽  
Author(s):  
G L Dohm ◽  
E A Newsholme
Keyword(s):  
Metabolic Control ◽  
Pyruvate Kinase ◽  
Pyruvate Carboxylase ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Prolonged Exercise ◽  
Allosteric Effectors ◽  
Fructose 1,6 Bisphosphatase ◽  
Metabolite Concentrations ◽  
Fructose 1,6 Bisphosphate ◽  
Hexose Phosphates

Prolonged exercise increased the concentrations of the hexose phosphates and phosphoenolpyruvate and depressed those of fructose 1,6-bisphosphate, triose phosphates and pyruvate in the liver of the rat. Since exercise increases gluconeogenic flux, these changes in metabolite concentrations suggest that metabolic control is exerted, at least, at the fructose 6-phosphate/fructose 1,6-bisphosphate and phosphoenolpyruvate/pyruvate substrate cycles. Exercise increased the maximal activities of glucose 6-phosphatase, fructose 1,6-bisphosphatase, pyruvate kinase and pyruvate carboxylase in the liver, but there were no changes in those of glucokinase, 6-phosphofructokinase and phosphoenolpyruvate carboxykinase. Exercise changed the concentrations of several allosteric effectors of the glycolytic or gluconeogenic enzymes in liver; the concentrations of acetyl-CoA, ADP and AMP were increased, whereas those of ATP, fructose 1,6-bisphosphate and fructose 2,6-bisphosphate were decreased. The effect of exercise on the phosphorylation-dephosphorylation state of pyruvate kinase was investigated by measuring the activities under conditions of saturating and subsaturating concentrations of substrate. The submaximal activity of pyruvate kinase (0.5 mM-phosphoenolpyruvate), expressed as percentage of Vmax., decreased in the exercised animals to less than half that found in the controls. These changes suggest that hepatic pyruvate kinase is less active during exercise, possibly owing to phosphorylation of the enzyme, and this may play a role in increasing the rate of gluconeogenesis.

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