ABSTRACT
Glycogen in Saccharomyces cerevisiae is present in two pools, one soluble and intracellular, the other present in the cell wall and rendered water-insoluble owing to its covalent linkage to cell wall beta-glucan. The insoluble glycogen fraction was solubilized using beta-1,3-glucanase. The alpha beta-glucan complex obtained showed intense red staining with iodine and was isolated from free beta-glucans by affinity chromatography using concanavalin A sepharose 4B. Further use of molecular sieving has confirmed that glycogen is linked to beta-glucan as the non-retained fraction on Biogel P2 split into two peaks on treatment with amyloglucosidase. Partial acid hydrolysis and subsequent paper chromatography of the alpha beta-glucan complex isolated revealed the presence of gentiobiose and other higher oligosaccharides, indicating that glycogen is linked to beta-1,3-glucan through a beta-1,6 branch. The insoluble glycogen can be extracted in a soluble form by acetic acid treatment and is known as acid-soluble glycogen. The presence of glycogen in the cell wall is confirmed by controlled enzymatic release of alpha beta-glucan complex using lyticase from Arthobacter luteus without disruption of the plasma membrane, as can be visualized using electron microscopy.
