Glycolytic Shunts Replenish the Calvin-Benson-Bassham Cycle as Anaplerotic Reactions in Cyanobacteria  

作　　者：Alexander Makowka Lars Nichelmann Dennis Schulze Katharina Spengler Christoph Wittmann Karl Forchhammer Kirstin Gutekunst 

机构地区：[1]Department of Biology,Botanical Institute,University Kiel,24118 Kiel,Germany [2]Institute for Systems Biotechnology,Saarland University,66123 Saarbrucken,Germany [3]Organismic Interactions Department,Interfaculty Institute for Microbiology and Infection Medicine,University

出　　处：《Molecular Plant》2020年第3期471-482,共12页分子植物（英文版）

基　　金：financed by grants from the Deutsche Forschungsgemeinschaft(GU1522/1-1,GU1522/2-1,WI1796/3-1,and FOR 2816);the Bundesministerium fur Bildung und Forschung(FP309).

摘　　要：The recent discovery of the Entner-Doudoroff(ED)pathway as a third glycolytic route beside Embden-Meyerhof-Parnas(EMP)and oxidative pentose phosphate(OPP)pathway in oxygenic photoautotrophs requires a revision of their central carbohydrate metabolism.In this study,unexpectedly,we observed that deletion of the ED pathway alone,and even more pronounced in combination with other glycolytic routes,diminished photoautotrophic growth in continuous light in the cyanobacterium Synechocystis sp.PCC 6803.Furthermore,we found that the ED pathway is required for optimal glycogen catabolism in parallel to an operating Calvin-Benson-Bassham(CBB)cycle.It is counter-intuitive that glycolytic routes,which are a reverse to the CBB cycle and do not provide any additional biosynthetic intermediates,are important under photoautotrophic conditions.However,observations on the ability to reactivate an arrested CBB cycle revealed that they form glycolytic shunts that tap the cellular carbohydrate reservoir to replenish the cycle.Taken together,our results suggest that the classical view of the CBB cycle as an autocatalytic,completely autonomous cycle that exclusively relies on its own enzymes and C02 fixation to regenerate ribulose-1,5-bisphosphate for Rubisco is an oversimplification.We propose that in common with other known autocatalytic cycles,the CBB cycle likewise relies on anaplerotic reactions to compensate for the depletion of intermediates,particularly in transition states and under fluctuating light conditions that are common in nature.

关 键 词：central carbohydrate metabolism Calvin-Benson-Bassham cycle Entner-Doudoroff pathway oxidative pentose phosphate pathway Embden-Meyerhof-Parnas pathway CYANOBACTERIA 

分 类 号：Q94[生物学—植物学]