Department of Bioinformatics Engineering, Graduate School of Information Science and Technology, Osaka University, 1-5 Yamadaoka, Suita, Osaka 565-0871, Japan.
J Biosci Bioeng. 2019 Oct;128(4):424-428. doi: 10.1016/j.jbiosc.2019.03.016. Epub 2019 Apr 10.
In photosynthetic organisms, such as cyanobacteria, ATP and NADPH are generated through the light reaction, and then are used for CO fixation in the dark reaction. As light intensity always fluctuates under natural conditions, balancing the cofactor regeneration and consumption is essential to maintain active CO fixation as well as for metabolic engineering of strains that produce biochemicals. In this study, a time-resolved metabolome analysis of Synechocystis sp. PCC 6803 (PCC6803) was conducted to investigate a metabolic adaptation at 0-15 min after a sudden shift from light to dark conditions. Rapid accumulation of sedoheptulose 7-phosphate, ribulose 5-phosphate, xylulose 5-phosphate, and 6-phosphogluconate suggested that the central metabolism of PCC6803 was regulated by inactivation of phosphoribulokinase and activation of glucose-6-phosphate dehydrogenase (G6PDH) probably via the redox regulation. The culture and metabolic profile of the Δzwf strain lacking G6PDH showed that the role of G6PDH in regeneration of NADPH could be complemented by the activation of isocitrate dehydrogenase in the TCA cycle, indicating the importance of the rapid regulation of NADPH regeneration after the shift to dark conditions. The mechanism underlying metabolic regulation is also useful for metabolic engineering of PCC6803, as the Δzwf strain produced higher amount of organic acids than wild type.
在光合作用生物中，例如蓝细菌，通过光反应生成 ATP 和 NADPH，然后在暗反应中用于 CO 固定。由于自然条件下的光强度总是波动的，因此平衡辅助因子的再生和消耗对于维持活跃的 CO 固定以及代谢工程菌株生产生物化学物质是至关重要的。在这项研究中，对 Synechocystis sp. PCC 6803 (PCC6803) 进行了时间分辨代谢组分析，以研究在从光到暗条件的突然转变后 0-15 分钟时的代谢适应。 sedoheptulose 7-phosphate、ribulose 5-phosphate、xylulose 5-phosphate 和 6-phosphogluconate 的快速积累表明，PCC6803 的中心代谢受到通过可能通过氧化还原调节失活的磷酸核糖激酶和激活葡萄糖-6-磷酸脱氢酶 (G6PDH) 的调节。缺乏 G6PDH 的 Δzwf 菌株的培养和代谢谱表明，G6PDH 在 NADPH 再生中的作用可以通过 TCA 循环中的异柠檬酸脱氢酶的激活来补充，这表明在暗条件下转变后 NADPH 再生的快速调节非常重要。代谢调节的机制对于 PCC6803 的代谢工程也很有用，因为与野生型相比，Δzwf 菌株产生了更多的有机酸。
