Regulation of glycogen metabolism in yeast and bacteria

Abstract

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 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 guarantee 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 post-transcriptional levels, which 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, especial emphasis is given to aspects related with genetic regulation of glycogen metabolism and its connection with other biological processes.

Double Knockout Mutants of Arabidopsis Grown under Normal Conditions Reveal that the Plastidial Phosphorylase Isozyme Participates in Transitory Starch Metabolism

“…Ample evidence has been presented that these enzymes are essential biosynthetic enzymes (Ballicora et al, 2003;Zeeman et al, 2010;Roach et al, 2012;Palm et al, 2013). Furthermore, it is widely accepted that in glycogenstoring cells, phosphorylase is indispensible for the degradation of the storage polysaccharide (Hwang et al, 1989;Alonso-Casajús et al, 2006;Wilson et al, 2010;Roach et al, 2012;Gazzerro et al, 2013).…”

Molecular basis of the 14-3-3 protein-dependent activation of yeast neutral trehalase Nth1

“…Trehalose is found in many organisms ranging from bacteria and fungi to invertebrates and higher plants, where it fulfills a number of physiological roles (14,15). In yeast, trehalose is a major storage carbohydrate, carbon source, and stress protectant, and its hydrolysis is catalyzed mainly by neutral trehalase with a pH optimum of about 7, encoded by two genes, NTH1 and NTH2, with NTH1 being more active (16). Compared with trehalases from prokaryotic and higher eukaryotic organisms, yeast neutral trehalases possess an N-terminal extension that contains four cAMP-dependent protein kinase (PKA) phosphorylation sites (S20, S21, S60, and S83 in Saccharomyces cerevisiae Nth1) and the calcium-binding EF-hand-like motif (Fig.…”

A sensitive method for confocal fluorescence microscopic visualization of starch granules in iodine stained samples

“…7 In Arabidopsis, genetic evidence showing that transitory starch biosynthesis occurs solely by the AGP pathway has been obtained from the characterization of the adg1-1 and aps1 AGP mutants.…”

“…6 Furthermore, evidence has been provided showing the occurrence of various important sources, other than GlgC, of ADP-glucose linked to glycogen biosynthesis in different bacterial species. 7 In Arabidopsis, genetic evidence showing that transitory starch biosynthesis occurs solely by the AGP pathway has been obtained from the characterization of the adg1-1 and aps1 AGP mutants. [8][9][10] Leaves of these mutants display an apparent starch-less phenotype when macroscopically analyzed upon staining with iodine solutions, and when subjected to quantitative-type enzymatic tests for starch measurement.…”