Glycogen is a branched polysaccharide of high molecular mass that is used as a storage carbohydrate. In S. cerevisiae, glycogen is typically catabolized to glucose-1-phosphate and glucose by the Gph1p glycogen phosphorylase and the Gdb1p debranching enzyme (5). However, during sporulation, glycogen is rapidly catabolized to glucose by the Sga1p glucoamylase (5).

SGA1 expression is inhibited by Rme1p during vegetative growth, and is induced by Ime1p in diploid cells during late sporulation (6). Co-localization experiments suggest that Sga1p may localize to the vacuole (2). The Sga1p amylo-(1,4-1,6)-glucosidase is capable of degrading glycogen, starch, maltotriose, and maltose into glucose, but exhibits maximum activity toward glycogen at pH 5.5 (5, 2). The role of glycogen degradation during sporulation is not fully understood, as approximately 90% of sga1 homozygous null mutants are able to produce viable spores (5).

Last updated: 2005-08-25