The effect of glucose on liver glycogen synthase phosphatase activity in the presence of ATP-Mg

1988 ◽  
Vol 264 (1) ◽  
pp. 302-309 ◽  
Author(s):  
Daniel P. Gilboe ◽  
Frank Q. Nuttall
Keyword(s):  
Phosphatase Activity ◽  
Glycogen Synthase ◽  
Liver Glycogen ◽  
Effect Of Glucose

In vivo phosphorylation of liver glycogen synthase. Effect of glucose and glucagon treatment of liver cells on the distribution of the [32P] phosphate

1993 ◽  
Vol 71 (1-2) ◽  
pp. 90-96 ◽  
Author(s):  
Agnes W. H. Tan ◽  
Frank Q. Nuttall
Keyword(s):  
High Pressure ◽  
Liquid Chromatography ◽  
Rat Liver ◽  
Glycogen Synthase ◽  
Liver Glycogen ◽  
Liver Cells ◽  
Phosphorylation State ◽  
Glucose Treatment ◽  
Effect Of Glucose

Glycogen synthase was phosphorylated in vivo by perfusing rat liver or incubating liver cells with [32P]phosphate. It was then isolated by immunoprecipitation and subjected to exhaustive tryptic proteolysis. The trypsin-derived [32P]phosphopeptides were separated by high pressure liquid chromatography (HPLC). Incubation of in vivo phosphorylated synthase with endogenous synthase phosphatase to convert synthase D to synthase R resulted in removal of phosphate from all of the labeled phosphopeptides. In prelabeled liver cells treated with glucagon or glucose, the activities of synthase and phosphorylase changed in the direction expected. The total labeling in the immunoprecipitated synthase was found to be increased to 126% and decreased to 67% of the control with glucagon and glucose treatment, respectively. When the HPLC [32P]phosphopeptide profile of synthase from glucagon-treated animals was compared with that of controls, there were only minor differences in the two profiles. All the peaks were present and the proportion of labeling in each remained similar. There also was only a modest change in the [32P]phosphopeptide profile with glucose treatment when compared with that of controls. These results indicate that regulation of synthase activity in the hepatocyte involves changes in phosphorylation at multiple sites. Indeed, in 32P-labeled liver cells, all of the labeled sites appeared to be involved.Key words: glycogen synthase, liver, phosphorylation state, glucose treatment, glucagon treatment.

Opposite effects of hyperglycemia and insulin deficiency on liver glycogen synthase phosphatase activity in the diabetic rat

Diabetes ◽  
1993 ◽  
Vol 42 (2) ◽  
pp. 363-366 ◽  
Author(s):  
L. Lavoie ◽  
D. Dimitrakoudis ◽  
A. Marette ◽  
B. Annabi ◽  
A. Klip ◽  
...  
Keyword(s):  
Phosphatase Activity ◽  
Glycogen Synthase ◽  
Liver Glycogen ◽  
Diabetic Rat ◽  
Insulin Deficiency

Opposite Effects of Hyperglycemia and Insulin Deficiency on Liver Glycogen Synthase Phosphatase Activity in the Diabetic Rat

Diabetes ◽  
1993 ◽  
Vol 42 (2) ◽  
pp. 363-366 ◽  
Author(s):  
L. Lavoie ◽  
D. Dimitrakoudis ◽  
A. Marette ◽  
B. Annabi ◽  
A. Klip ◽  
...  
Keyword(s):  
Phosphatase Activity ◽  
Glycogen Synthase ◽  
Liver Glycogen ◽  
Diabetic Rat ◽  
Insulin Deficiency

Alteration of hepatic glycogen synthase phosphatase activity by insulin deficiency

1981 ◽  
Vol 240 (5) ◽  
pp. E539-E543
Author(s):  
T. B. Miller ◽  
J. J. Vicalvi ◽  
A. K. Garnache
Keyword(s):  
Phosphatase Activity ◽  
Rat Liver ◽  
Glycogen Phosphorylase ◽  
Glycogen Synthase ◽  
Liver Glycogen ◽  
Diabetic Rats ◽  
Hepatic Glycogen ◽  
Molecular Alteration ◽  
Activity Inhibition ◽  
Related Defect

Perfused livers from normal and alloxan-diabetic rats were studied to determine whether the diabetes-related decrease in glycogen synthase phosphatase was due to an alteration of the synthase molecule, an increase in synthase phosphatase activity inhibition by phosphorylase a, or generation of inhibitor of the phosphatase. With purified rat liver synthase as substrate for the phosphatase, the diabetic tissue remained 90–95% deficient in the ability to catalyze synthase D to I conversion, showing that the defect cannot be solely due to an altered substrate. When synthase phosphatase assays were carried out in the presence of rat liver glycogen phosphorylase antiserum, phosphatase activity remained 70–75% deficient in diabetic tissue. Therefore, the defect cannot be attributed to increased inhibition of synthase phosphatase by increased amounts of phosphorylase a. When synthase phosphatase assays were run by mixing extracts from normal and diabetic livers, phosphatase activity was additive, indicating that a phosphatase inhibitor was probably not involved in the phosphatase deficiency in the diabetic. These data are consistent with the hypothesis that the diabetes-related defect in glucose regulation of hepatic glycogen synthase is due to a molecular alteration or a deficiency of a specific glycogen synthase phosphatase.

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