Rerouting of carbon flux in a glycogen mutant of cyanobacteria assessed via isotopically non-stationary 13C metabolic flux analysis
Rerouting of carbon flux in a glycogen mutant of cyanobacteria assessed via isotopically non-stationary 13C metabolic flux analysis
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DOI：
10.1002/bit.26350
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发表时间：
2017-10-01
影响因子：
3.8
通讯作者：
Wangikar, Pramod P.
中科院分区：
文献类型：
--
作者：
Hendry, John I.;Prasannan, Charulata;Wangikar, Pramod P.
蓝藻是一种数量上占优势的门，由于其良好的生理特性、高光合效率和易于遗传操作而在生物燃料应用中引起了人们的关注。然而，蓝藻代谢的定量方面受到了有限的关注。在本研究中，我们进行了同位素非稳态C-13代谢通量分析（INST-C-13-MFA）来分析模型蓝藻聚藻球菌PCC 7002的糖原合成酶缺陷突变菌株（glgA-I glgA-II）的碳重定向。在平衡的光自养生长过程中，10-20%的固定碳通过在蓝藻门中保守的途径以糖原的形式储存。我们的研究结果表明，糖原合成酶基因的缺失协调了代谢网络中各个部分碳分布的级联效应。原本注定要被纳入糖原的碳被部分转移到其他储存分子，如葡萄糖甘油和蔗糖。其余部分主要通过糖酵解和三羧酸循环在代谢网络中分配。碳水化合物合成通量的降低和葡萄糖-1-磷酸节点分布的改变表明该网络具有灵活性。此外，糖原生物合成反应的可逆性表明存在无效循环。通量平衡分析也预测了类似的碳再分配。结果是显著的代谢工程努力与蓝藻，其中固定碳需要重新路由到感兴趣的产品。Biotechnol。Bioeng。2017;114: 2298 - 2308。(c) 2017 Wiley期刊公司
Cyanobacteria, which constitute a quantitatively dominant phylum, have attracted attention in biofuel applications due to favorable physiological characteristics, high photosynthetic efficiency and amenability to genetic manipulations. However, quantitative aspects of cyanobacterial metabolism have received limited attention. In the present study, we have performed isotopically non-stationary C-13 metabolic flux analysis (INST-C-13-MFA) to analyze rerouting of carbon in a glycogen synthase deficient mutant strain (glgA-I glgA-II) of the model cyanobacterium Synechococcus sp. PCC 7002. During balanced photoautotrophic growth, 10-20% of the fixed carbon is stored in the form of glycogen via a pathway that is conserved across the cyanobacterial phylum. Our results show that deletion of glycogen synthase gene orchestrates cascading effects on carbon distribution in various parts of the metabolic network. Carbon that was originally destined to be incorporated into glycogen gets partially diverted toward alternate storage molecules such as glucosylglycerol and sucrose. The rest is partitioned within the metabolic network, primarily via glycolysis and tricarboxylic acid cycle. A lowered flux toward carbohydrate synthesis and an altered distribution at the glucose-1-phosphate node indicate flexibility in the network. Further, reversibility of glycogen biosynthesis reactions points toward the presence of futile cycles. Similar redistribution of carbon was also predicted by Flux Balance Analysis. The results are significant to metabolic engineering efforts with cyanobacteria where fixed carbon needs to be re-routed to products of interest. Biotechnol. Bioeng. 2017;114: 2298-2308. (c) 2017 Wiley Periodicals, Inc.