Regulation of glycogen metabolism in response to the autotrophy-heterotrophy switch in Cyanobacteria
Glycogen is the major carbon-storage compound in cyanobacteria and its metabolism is central for metabolic homeostasis and essential to survive periods of darkness or macronutrient deprivation such as nitrogen starvation. In Synechocystis sp. PCC 6803 glycogen synthesis and degradation involves a set of paralogous enzymes, which have apparently distinct functional roles1 and involves specific catabolic pathways2. A key for the initiation of glycogen synthesis is the inhibition of phophoglycerate mutase by the PII-controlled PirC protein3. Conversely, mobilization of glycogen upon resuscitation form nitrogen chlorosis is triggered by ongoing GS-GOGAT cycle4, which activates the glycogen catabolic machinery. Thereby, phosphoglucomutase acts as key metabolic valve that controls the catabolism of glycogen5.
1. Koch, K. Doello, S. Gutekunst, K. & Forchhammer, K. 2019. PHB is produced from Glycogen turn-over during nitrogen starvation in Synechocystis sp. PCC 6803. (2019) Int. J. Mol. Sci. 20 (8): 1942
2. Makowka, A., Nichelmann, L., Schulze, D., Spengler, K., Wittmann, C., Forchhammer, K & Gutekunst K. 2020. Glycolytic Shunts Replenish the Calvin–Benson–Bassham Cycle as Anaplerotic Reactions in Cyanobacteria. Molecular plant 13: 471-482
3. Orthwein, T, Scholl, J., Spät, P., Lucius, S., Koch, M., Macek, B. Hagemann, M. & Forchhammer, K. 2021.The novel PII-interactor PirC identifies phosphoglycerate mutase as key control point of carbon storage metabolism in cyanobacteria. PNAS e2019988118
4. Doello, S., Burkhardt, M. & Forchhammer, K. 2021. The essential role of sodium bioenergetics and ATP homeostasis in the developmental transitions of a cyanobacterium. Curr Biol. doi.org/10.1016/j.cub.2021.01.065
5. Doello, S., Neumann, N., Spät, P., Maček, B & Forchhammer, K. 2021Phosphoglucomutase as central hub in the control of glycogen metabolism (submitted)
Prof. Karl Forchhammer
University of Tübingen
Department of Organismic Interactions
Auf der Morgenstelle 28, 72076 Tübingen, Germany
Dr. Sofia Doello
Niels Neumann M.Sc.