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Cyclic AMP-Dependent Catabolite Repression Is the Dominant Control Mechanism of Metabolic Fluxes under Glucose Limitation in Escherichia coli▿ †

机译:依赖环AMP的分解代谢物阻遏是葡萄糖限制下大肠杆菌中代谢通量的主要控制机制。

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摘要

Although a whole arsenal of mechanisms are potentially involved in metabolic regulation, it is largely uncertain when, under which conditions, and to which extent a particular mechanism actually controls network fluxes and thus cellular physiology. Based on 13C flux analysis of Escherichia coli mutants, we elucidated the relevance of global transcriptional regulation by ArcA, ArcB, Cra, CreB, CreC, Crp, Cya, Fnr, Hns, Mlc, OmpR, and UspA on aerobic glucose catabolism in glucose-limited chemostat cultures at a growth rate of 0.1 h−1. The by far most relevant control mechanism was cyclic AMP (cAMP)-dependent catabolite repression as the inducer of the phosphoenolpyruvate (PEP)-glyoxylate cycle and thus low tricarboxylic acid cycle fluxes. While all other mutants and the reference E. coli strain exhibited high glyoxylate shunt and PEP carboxykinase fluxes, and thus high PEP-glyoxylate cycle flux, this cycle was essentially abolished in both the Crp and Cya mutants, which lack the cAMP-cAMP receptor protein complex. Most other mutations were phenotypically silent, and only the Cra and Hns mutants exhibited slightly altered flux distributions through PEP carboxykinase and the tricarboxylic acid cycle, respectively. The Cra effect on PEP carboxykinase was probably the consequence of a specific control mechanism, while the Hns effect appears to be unspecific. For central metabolism, the available data thus suggest that a single transcriptional regulation process exerts the dominant control under a given condition and this control is highly specific for a single pathway or cycle within the network.
机译:尽管整个机制可能涉及代谢调控,但很大程度上不确定何时,在何种条件下以及在何种程度上实际控制网络通量从而控制细胞生理。根据大肠杆菌突变体的13C通量分析,我们阐明了ArcA,ArcB,Cra,CreB,CreC,Crp,Cya,Fnr,Hns,Mlc,OmpR和UspA参与的全球转录调控与葡萄糖代谢过程的相关性。有限的化学恒温器培养物,其生长速度为0.1 h-1。到目前为止,最相关的控制机制是依赖环AMP(cAMP)的分解代谢物阻遏作为磷酸烯醇丙酮酸(PEP)-乙醛酸酯循环的诱因,因此三羧酸循环通量较低。尽管所有其他突变体和参比大肠杆菌菌株均表现出较高的乙醛酸分流和PEP羧激酶通量,因此具有较高的PEP-乙醛酸循环通量,但在缺少cAMP-cAMP受体蛋白的Crp和Cya突变体中,该循环基本上都被取消了。复杂。大多数其他突变在表型上是沉默的,只有Cra和Hns突变体分别通过PEP羧激酶和三羧酸循环表现出略微改变的通量分布。对PEP羧激酶的Cra效应可能是特定控制机制的结果,而Hns效应似乎是非特异性的。对于中枢代谢,现有数据因此表明,在给定条件下,单个转录调控过程将发挥主要控制作用,并且这种控制对于网络中的单个途径或循环具有高度特异性。

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