Ultrasensitive behavior in the synthesis of storage polysaccharides in cyanobacteria

Diego F. Gómez-Casati, Sonia Cortassa, Miguel A. Aon, Alberto A. Iglesias

Research output: Contribution to journalArticlepeer-review

Abstract

The glycogen synthetic pathway operates ultrasensitively as a function of the ADPglucose pyrophosphorylase (ADPGlcPPase) allosteric effectors, 3-phosphoglycerate and Pi, in permeabilized cells of the cyanobacterium Anabaena PCC 7120. In vitro data previously showed that the ultrasensitive behavior of ADPGlcPPase depends upon cross-talk between the two allosteric effectors, the enzyme's response being additionally modulated by molecular crowding [D.F. Gómez Casatiet al. (2000) Biochem J 350:139-147]. In the present work we show, experimentally and with a mathematical model, that α-1,4-glucan synthesis is also ultrasensitive in cells due to the propagation of the switch-like behavior of ADPGlcPPase to the synthetic pathway. Amplifications of up to 20-fold in storage-polysaccharide synthesis can be achieved with a modest 6.7-fold increase in 3-phosphoglycerate in the presence of 5 mM Pi in contrast to the 30-fold necessary in its absence. This is the first time that this phenomenon has been reported to occur in the glycogen synthetic pathway of a photosynthetic prokaryote. The implications of the results for plant cell physiology during light-dark transitions are discussed.

Original languageEnglish (US)
Pages (from-to)969-975
Number of pages7
JournalPlanta
Volume216
Issue number6
DOIs
StatePublished - Apr 1 2003

Keywords

  • ADPglucose pyrophosphorylase
  • Anabaena
  • Glycogen/starch synthesis
  • Molecular crowding
  • Permeabilized cyanobacteria
  • Ultrasensitivity (of enzymes)

ASJC Scopus subject areas

  • Genetics
  • Plant Science

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