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Glycogen synthase activation by sugars in isolated hepatocytes
C J Ciudad1, A Carabaza, F Bosch
1Department de Bioquímica y Biologia Molecular, Universidad Autónoma de Barcelona, Spain.
Archives of Biochemistry and Biophysics
|July 1, 1988
Summary
Sugars activate glycogen synthase independently of phosphorylase a, revealing a nonsequential activation mechanism in liver cells. This process is influenced by intracellular glucose 6-phosphate and adenine nucleotide levels.
Area of Science:
- Biochemistry
- Cellular Metabolism
- Enzymology
Background:
- Glycogen synthase is a key enzyme in glycogen synthesis.
- Its regulation is complex and involves various metabolites.
- Understanding sugar-induced activation is crucial for metabolic research.
Purpose of the Study:
- To investigate the activation of glycogen synthase by different sugars.
- To correlate this activation with phosphorylase a activity and intracellular metabolite levels.
- To elucidate the mechanism of sugar-induced glycogen synthase activation in hepatocytes.
Main Methods:
- Assaying glycogen synthase and phosphorylase a activities.
- Measuring intracellular concentrations of glucose 6-phosphate and adenine nucleotides (ATP, AMP).
- Analyzing kinetic parameters (M0.5 and S0.5) of glycogen synthase.
Main Results:
- All tested sugars activated glycogen synthase.
- Sugar effects on phosphorylase a activity varied.
- Specific sugars altered adenine nucleotide and glucose 6-phosphate levels, impacting glycogen synthase activation.
- Activation correlated with decreased kinetic constants for glucose 6-phosphate and UDP-glucose.
Conclusions:
- Hepatocyte glycogen synthase activation by sugars occurs via a nonsequential mechanism.
- This activation is triggered by changes in glucose 6-phosphate and adenine nucleotide concentrations.
- Metabolite control plays a significant role in sugar-induced glycogen synthase activation.