Comparative 13C Metabolic Flux Analysis of Pyruvate Dehydrogenase Complex-Deficient, L-Valine-Producing Corynebacterium glutamicum
Comparative 13C Metabolic Flux Analysis of Pyruvate Dehydrogenase Complex-Deficient, L-Valine-Producing Corynebacterium glutamicum
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DOI：
10.1128/aem.00575-11
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发表时间：
2011-09-01
影响因子：
4.4
通讯作者：
Noack, Stephan
中科院分区：
文献类型：
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作者：
Bartek, Tobias;Blombach, Bastian;Noack, Stephan
利用C.谷氨酸菌株缺失活性丙酮酸脱氢酶复合物（PDHC）。野生型艰难梭通过C-13代谢通量分析比较了谷氨酸和四种PDHC缺陷型菌株的代谢产物，特别是糖酵解和戊糖磷酸途径（PPP）之间的分流比。与野生型相比，通过PPP的碳通量为69% +/-14%，在PDHC缺陷型菌株中观察到PPP通量的强烈增加，最大为113% +/-22%。分流比的变化可以通过L-缬氨酸形成对NADPH的需求增加来解释。因此，将催化NADH可逆转化为NADPH的大肠杆菌转氢酶PntAB导入L-缬氨酸产生菌C.谷氨酸菌菌株引起PPP通量降低至57% +/-6%，这低于野生型分流比。因此，转氢酶活性为充足的NADPH供应提供了另一种观点，这与大多数氨基酸生产系统相关。此外，如对于L-缬氨酸所证明的，由于经由PPP的二氧化碳形成的同时减少，该旁路导致产物产率的显著增加。
L-Valine can be formed successfully using C. glutamicum strains missing an active pyruvate dehydrogenase enzyme complex (PDHC). Wild-type C. glutamicum and four PDHC-deficient strains were compared by C-13 metabolic flux analysis, especially focusing on the split ratio between glycolysis and the pentose phosphate pathway (PPP). Compared to the wild type, showing a carbon flux of 69% +/- 14% through the PPP, a strong increase in the PPP flux was observed in PDHC-deficient strains with a maximum of 113% +/- 22%. The shift in the split ratio can be explained by an increased demand of NADPH for L-valine formation. In accordance, the introduction of the Escherichia coli transhydrogenase PntAB, catalyzing the reversible conversion of NADH to NADPH, into an L-valine-producing C. glutamicum strain caused the PPP flux to decrease to 57% +/- 6%, which is below the wild-type split ratio. Hence, transhydrogenase activity offers an alternative perspective for sufficient NADPH supply, which is relevant for most amino acid production systems. Moreover, as demonstrated for L-valine, this bypass leads to a significant increase of product yield due to a concurrent reduction in carbon dioxide formation via the PPP.