The physiologic role of the Entner-Doudoroff Pathway in Synechocystis
Oxygenic photoautotrophs as cyanobacteria, moss, fern, algae and plants were long thought to oxidize their carbohydrates exclusively via two glycolytic routes, the Emden-Meyerhof-Parnas (EMP) pathway (often referred to as glycolysis) and the oxidative pentose phosphate (OPP) pathway. We found that a third glycolytic route, the Entner-Doudoroff (ED) pathway operates in these organisms, which was brought via endosymbiotic gene transfer from cyanobacteria to the plant lineage (Chen et al., 2016). At the same time a fourth glycolytic route, the phosphoketolase pathway, was described to operate in cyanobacteria, but not in plants (Xiong et al., 2015). Our studies aim to understand the physiological role of the ED pathway in the cyanobacterium Synechocystis sp PCC 6803 and to particularly examine its connection to the light reaction of photosynthesis and CO2-fixation. We recently found that glycolytic shunts are formed that tap the glycogen pool to replenish the Calvin-Benson-Bassham (CBB) cycle of CO2-fixation in transition states from darkness to light (Makowka et al., 2020). Glycolytic routes and the CBB cycle are obviously tightly intertwined and require a delicate fine-tuning for the autotrophy-heterotrophy switch.
• Chen, X., Schreiber, K., Appel, J., Makowka, A., Fähnrich, B., Roettger, M., . . . Gutekunst, K. (2016). The Entner–Doudoroff pathway is an overlooked glycolytic route in cyanobacteria and plants. Proceedings of the National Academy of Sciences, 113(19), 5441-5446. doi: 10.1073/pnas.1521916113
• 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(3), 471-482. doi: https://doi.org/10.1016/j.molp.2020.02.002
• Xiong, W., Lee, T.-C., Rommelfanger, S., Gjersing, E., Cano, M., Maness, P.-C., . . . Yu, J. (2015). Phosphoketolase pathway contributes to carbon metabolism in cyanobacteria. Nature Plants, 2, 15187. doi: 10.1038/nplants.2015.187
Prof. Dr. Kirstin Gutekunst
Institut für Biologie
Heinrich-Plett-Str. 40, 34109 Kassel, Germany
Marius Theune M.Sc.
Dr. Sarah Hildebrandt