Disruption of the gene pgil of Saccharomyces cerevisiae, which codes for phosphoglucose isomerase, results in a dramatic increase in the amount of intracellular glycogen in early exponential cultures. The level of glucose 6-phosphate was much higher in mutant than in wild-type cells. Phosphorylase a activity and the state of activation of glycogen synthase were also investigated. Phosphorylase a activity was rather low along the culture in wild-type cells, whereas it was consistently higher in mutants. Glycogen synthase was mostly in the active form in early-medium exponential cultures in wild-type cells whereas the activation state of this enzyme in mutant cells, although lower at the earlier steps of the culture, did not differ from wild-type cells at later stages. The fact that the intracellular levels of UDP-glucose are markedly increased in mutant cells suggest that the observed accumulation of glycogen results from a rise in substrate availability rather than from the activation of the enzyme responsible for the synthesis of the polysaccharide.

• PMID: 1397270
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Journal Article | Research Support, Non-U.S. Gov't

Authors

Corominas J, Clotet J, Fernández-Bañares I, Boles E, Zimmermann FK, Guinovart JJ, Ariño J

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