Pseudomonas putida KT2440 Strain Metabolizes Glucose through a Cycle Formed by Enzymes of the Entner-Doudoroff, Embden-Meyerhof-Parnas, and Pentose Phosphate Pathways
Pseudomonas putida KT2440 Strain Metabolizes Glucose through a Cycle Formed by Enzymes of the Entner-Doudoroff, Embden-Meyerhof-Parnas, and Pentose Phosphate Pathways
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DOI：
10.1074/jbc.m115.687749
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发表时间：
2015-10-23
影响因子：
4.8
通讯作者：
de Lorenzo, Victor
中科院分区：
文献类型：
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作者：
Nikel, Pablo I.;Chavarria, Max;de Lorenzo, Victor
土壤细菌恶臭假单胞菌KT2440缺乏功能性embp - meyerhoff - parnas （EMP）途径，已知糖酵解几乎完全通过enterner - doudoroff （ED）途径进行。为了研究这种代谢安排存在的原因，我们利用c -13标记的底物，结合定量生理学实验、代谢物定量和体外酶分析，在饱和和非饱和、准体内条件下，研究了该细菌葡萄糖培养物中质周和细胞质碳通量的分布。代谢通量分析表明，90%的糖被转化为葡萄糖酸盐，以6-磷酸葡萄糖酸盐的形式进入中央碳代谢，并进一步进入ED途径。值得注意的是，大约10%的磷酸三糖被发现可以循环利用，形成磷酸己糖。这组反应合并了ED、EMP（以糖异生方式运作）和戊糖磷酸途径的活动，形成了一个不可预见的代谢结构（EDEMP循环）。NADPH平衡的测定表明，恶臭p.p . putida KT2440的默认代谢状态的特征是轻微的分解代谢过剩，产生还原力。因此，依靠葡萄糖生长的细胞进行有利于NADPH形成的生化循环。由于NADPH不仅需要合成代谢功能，而且还需要抵消不同类型的环境应激，这种循环操作可能有助于这种细菌在其自然栖息地的生理体重。
The soil bacterium Pseudomonas putida KT2440 lacks a functional Embden-Meyerhof-Parnas (EMP) pathway, and glycolysis is known to proceed almost exclusively through the Entner-Doudoroff (ED) route. To investigate the raison d'etre of this metabolic arrangement, the distribution of periplasmic and cytoplasmic carbon fluxes was studied in glucose cultures of this bacterium by using C-13-labeled substrates, combined with quantitative physiology experiments, metabolite quantification, and in vitro enzymatic assays under both saturating and non-saturating, quasi in vivo conditions. Metabolic flux analysis demonstrated that 90% of the consumed sugar was converted into gluconate, entering central carbon metabolism as 6-phosphogluconate and further channeled into the ED pathway. Remarkably, about 10% of the triose phosphates were found to be recycled back to form hexose phosphates. This set of reactions merges activities belonging to the ED, the EMP (operating in a gluconeogenic fashion), and the pentose phosphate pathways to form an unforeseen metabolic architecture (EDEMP cycle). Determination of the NADPH balance revealed that the default metabolic state of P. putida KT2440 is characterized by a slight catabolic overproduction of reducing power. Cells growing on glucose thus run a biochemical cycle that favors NADPH formation. Because NADPH is required not only for anabolic functions but also for counteracting different types of environmental stress, such a cyclic operation may contribute to the physiological heftiness of this bacterium in its natural habitats.