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Glycogen hyperaccumulation in Saccharomyces cerevisiae ras2 mutant. A biochemical study
I Fernández-Bañares1, J Clotet, J Ariño
1Departament de Bioquímica i Biologia Molecular, Facultat de Veterinària, Universitat Autònoma de Barcelona, Spain.
FEBS Letters
|September 23, 1991
Summary
Yeast ras2 mutants accumulate excess glycogen due to increased glycogen synthase activity and activation. This occurs even with high glycogen phosphorylase a levels, suggesting a complex regulatory mechanism.
Area of Science:
- Biochemistry
- Molecular Biology
- Yeast Genetics
Background:
- Glycogen metabolism is crucial for cellular energy storage.
- The Ras2 protein in yeast plays a role in regulating cellular processes.
- Understanding glycogen accumulation mechanisms is important for metabolic research.
Purpose of the Study:
- To investigate the mechanism behind glycogen hyperaccumulation in yeast ras2 mutants.
- To determine the roles of glycogen synthase and glycogen phosphorylase a in this phenomenon.
Main Methods:
- Enzyme activity assays for glycogen synthase and glycogen phosphorylase a.
- Measurement of enzyme activation states.
- Quantification of intracellular glucose 6-phosphate and fructose 2,6-bisphosphate levels.
Main Results:
- Ras2 mutants exhibited 1.3-2.5 times higher total glycogen synthase activity.
- Glycogen synthase activation state increased throughout the growth phases in ras2 mutants, reaching full activation in stationary phase.
- Glycogen phosphorylase a activity was up to 40 times higher in ras2 mutants.
- Levels of glucose 6-phosphate and fructose 2,6-bisphosphate were slightly elevated in mutants.
Conclusions:
- Increased total glycogen synthase and its sustained high activation state are key factors in glycogen hyperaccumulation in ras2 mutants.
- The observed phenomenon occurs despite elevated glycogen phosphorylase a activity, indicating complex regulation.
- These findings provide insights into the intricate control of glycogen metabolism in yeast.