Abstract
Storage α-polyglucan in cyanobacteria is glycogen, which is regarded as the primitive form of starch (amylopectin) in plants. To elucidate the mechanism of amylopectin biosynthesis in plants, we isolated mutants of Synechococcus PCC 7942, affected in genes encoding glycogen synthase, glycogen branching enzyme (BE) and isoamylase (ISA). In addition to the single mutants, double mutants for BE and ISA were also obtained.
Analysis by capillary electrophoresis showed that glycogen of wild type Synechococcus, after debranching treatment, had the maximum chain length of DP 6. In BE mutant, the proportion of the peak chains of DP 6 was significantly decreased, while that of longer chains (≥10) was inversely increased. In ISA mutant, the amount of very short chains (DP 2 and 3) increased, but chains with length around 8 decreased. In BE/ISA double mutant, the cumulative effects in the corresponding single mutants were observed.
