Abstract
Previous analysis of the mutants of Synechococcus elongatus PCC 7942 defective in glycogen biosynthesis indicated that the storage polysaccharide has the significant role for the viability under high-salt and oxidative stresses. In the present study, mutants of phosphorylase (glgP), debranching enzyme (glgX) and α-1,4-glucanotransferase (malQ) have been constructed and characterized for the catabolic activity of glycogen accumulated in the cell.
The cellular content of glycogen in wild type (WT) cells remained constant throughout the diurnal cycles (12 h/12 h) of the growth and very little decrease was observed in the dark period. In contrast, the glycogen breakdown was highly stimulated when WT cells were exposed to 0.2 M NaCl in the continuous darkness. Under the same conditions, the activity of glycogen degradation in the glgP, glgX and malQ mutants was markedly reduced as compared to WT. It is therefore concluded that these enzymes are responsible for the glycogen catabolism in cyanobacteria.
