Starch and glycogen phosphorylases play opposite functions in reserve polysaccharide metabolisms

Dauvillée, D.1, Alonso-Casajús, N.2, Chochois, V.1, Steup, M.3, Pozueta-Romero, J.2, and Ball, S.1.

1UMR8576 CNRS, Universite« de Lille, 59655 Villeneuve d'Ascq, France 2Agrobioteknologiako Instituta, Nafarroako Unibertsitate Publikoa and Consejo Superior de Investigaciones Científicas, Mutiloako etorbidea zenbaki gabe, 31192 Mutiloabeti, Nafarroa, Spain 3Plant Physiology, Institute of Biochemistry and Biology, University of Potsdam, 14476 Potsdam-Golm, Germany

Glycogen and starch represent the two major forms of storage polysaccharides found in living organisms. While glycogen is accumulated in a great diversity of organisms (bacteria, cyanobacteria, mammal cells), starch is only observed in photosynthetic eukaryotes. We now report the full characterization of E. coli and C. reinhardtii homologous mutant strains defective for the same alpha glucan phosphorylase activity. The analysis performed on the E. coli mutant strains defective for glycogen phosphorylase confirms the major catabolic function suspected for this enzyme. However, the study performed on the Chlamydomonas mutants defective for plastidial starch phosphorylase brings to the light an unsuspected role of this enzyme in the normal process of starch synthesis. The opposite functions of the two reserve polysaccharide phosphorylase enzymes reveals one of the enzymatic specialization processes that occurred to switch from a glycogen-based to a starch-based metabolism.

e-mail address of presenting author: David.Dauvillee@univ-lille1.fr