Regulation of glycogen metabolism in yeast and bacteria

34 p., 10 figures and bibliography
Microorganisms have the capacity to utilize a variety of nutrients and adapt to continuously changing environmental conditions. Many microorganisms, including yeast and bacteria, accumulate carbon and energy reserves to cope with the starvation conditions temporarily present in the environment. Glycogen biosynthesis is a main strategy for such metabolic storage, and a variety of sensing and signaling mechanisms have evolved in evolutionarily distant species to ensure the production of this homopolysaccharide. At the most fundamental level, the processes of glycogen synthesis and degradation in yeast and bacteria share certain broad similarities. However, the regulation of these processes is sometimes quite distinct, indicating that they have evolved separately to respond optimally to the habitat conditions of each species. This review aims to highlight the mechanisms, both at the transcriptional and at the post-transcriptional level, that regulate glycogen metabolism in yeast and bacteria, focusing on selected areas where the greatest increase in knowledge has occurred during the last few years. In the yeast system, we focus particularly on the various signaling pathways that control the activity of the enzymes of glycogen storage. We also discuss our recent understanding of the important role played by the vacuole in glycogen metabolism. In the case of bacterial glycogen, special emphasis is placed on aspects related to the genetic regulation of glycogen metabolism and its connection with other biological processes.
This research was partially supported by the grant BIO2007-63915 from the Comisión Interministerial de Ciencia y Tecnología and Fondo Europeo de Desarrollo Regional (Spain), and by Iden Biotechnology S.L. M.M. acknowledges a postdoctoral contract from the I3P program of Consejo Superior de Investigaciones Científicas. The work of W.A.W. was supported in part by grant GM081810 from the National Institutes of Health, and work in the laboratory of P.J.R. was supported by grants DK27221 and DK42576, also from the National Institutes of Health.