摘要
Phosphohexomutases catalyze the interconversion between hexose-6-phosphate and hexose-1-phosphate and play important roles in polysaccharide synthesis.In Synechocystis sp.PCC 6803,sll0726 is predicted to encode PGM(phosphoglucomutase),slr1334is predicted to encode a PGM/PMM(phosphomannomutase)bifunction enzyme.In comparison to the wild type,a sll0726-null mutant showed 3.4%PGM activity but 45%–69%glycogen content.Down-regulation of slr1334,an essential gene,by using a copper regulated promoter further decreased the PGM activity in the sll0726::KmrPpetE-slr1334 double mutant to 0.3%of the wild type level.However,the glycogen content was not further decreased in parallel.In vitro,recombinant Sll0726 or Slr1334 showed predicted enzyme activities.Our results indicate that a relatively high level of glycogen can be maintained in Synechocystis mutants with low levels of PGM activity.The high PGM activity in the cyanobacterium may be required for turnover of glycogen or synthesis of other polysaccharides or oligosaccharides.
Phosphohexomutases catalyze the interconversion between hexose-6-phosphate and hexose-l-phosphate and play important roles in polysaccharide synthesis. In Synechocystis sp. PCC 6803, sl10726 is predicted to encode PGM （phosphoglucomutase）, slr1334 is predicted to encode a PGM/PMM （phosphomannomutase） bifunction enzyme. In comparison to the wild type, a sllO726-null mutant showed 3.4% PGM activity but 45%-69% glycogen content. Down-regulation of slr1334, an essential gene, by using a copper regulated promoter further decreased the PGM activity in the sllO726：：Kmr PpetE-slr1334 double mutant to 0.3% of the wild type level. However, the glycogen content was not further decreased in parallel. In vitro, recombinant Sl10726 or S1r1334 showed predicted enzyme activities. Our results indicate that a relatively high level of glycogen can be maintained in Synechocystis mutants with low levels of PGM activity. The high PGM activity in the cyanobacterium may be required for turnover of glycogen or synthesis of other polysaccharides or oligosaccharides.
基金
supported by the National Natural Science Foundation of China(30825003)
