Responses of the central metabolism in Escherichia coli to phosphoglucose isomerase and glucose-6-phosphate dehydrogenase knockouts
Responses of the central metabolism in Escherichia coli to phosphoglucose isomerase and glucose-6-phosphate dehydrogenase knockouts
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DOI：
10.1128/jb.185.24.7053-7067.2003
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发表时间：
2003-12-01
影响因子：
3.2
通讯作者：
Shimizu, K
中科院分区：
文献类型：
--
作者：
Hua, Q;Yang, C;Shimizu, K
利用葡萄糖和氨限量恒化器研究了大肠杆菌中枢碳代谢对磷酸葡萄糖异构酶和葡萄糖-6-磷酸(G6P)脱氢酶基因敲除突变的反应。利用基于[U-C-13]葡萄糖标记的通量比分析和代谢通量分析的互补方法以及细胞氨基酸、甘油和葡萄糖的二维核磁共振谱表征了野生型和基因敲除突变体的代谢网络结构和细胞内碳通量。磷酸葡萄糖异构酶的破坏导致戊糖磷酸途径作为葡萄糖分解代谢的主要途径，而通过Embden-Meyerhof-Parns途径和戊糖磷酸途径的非氧化分支的通量重路由弥补了G6P脱氢酶的缺乏。此外，还观察到了对基因敲除突变的额外的、意想不到的通量反应。最显著的是，乙醛酸分流在缺乏磷酸葡萄糖异构酶的大肠杆菌中被发现是活跃的。在这个突变菌株中，Entner-Doudoroff途径也对葡萄糖分解代谢的一小部分做出了贡献。此外，虽然G6P脱氢酶基因敲除对葡萄糖限制条件下的中枢代谢没有显著影响，但这种突变导致了广泛的溢出代谢和极低的三元酸循环通量。
The responses of Escherichia coli central carbon metabolism to knockout mutations in phosphoglucose isomerase and glucose-6-phosphate (G6P) dehydrogenase genes were investigated by using glucose- and ammonia-limited chemostats. The metabolic network structures and intracellular carbon fluxes in the wild type and in the knockout mutants were characterized by using the complementary methods of flux ratio analysis and metabolic flux analysis based on [U-C-13] glucose labeling and two-dimensional nuclear magnetic resonance (NMR) spectroscopy of cellular amino acids, glycerol, and glucose. Disruption of phosphoglucose isomerase resulted in use of the pentose phosphate pathway as the primary route of glucose catabolism, while flux rerouting via the Embden-Meyerhof-Parnas pathway and the nonoxidative branch of the pentose phosphate pathway compensated for the G6P dehydrogenase deficiency. Furthermore, additional, unexpected flux responses to the knockout mutations were observed. Most prominently, the glyoxylate shunt was found to be active in phosphoglucose isomerase-deficient E. coli. The Entner-Doudoroff pathway also contributed to a minor fraction of the glucose catabolism in this mutant strain. Moreover, although knockout of G6P dehydrogenase had no significant influence on the central metabolism under glucose-limited conditions, this mutation resulted in extensive overflow metabolism and extremely low tricarboxylic acid cycle fluxes under ammonia limitation conditions.