Study on roles of anaplerotic pathways in glutamate overproduction of <it>Corynebacterium glutamicum </it>by metabolic flux analysis

• Main Authors: Shioya Suteaki, Nagahisa Keisuke, Furusawa Chikara, Fujimura Koki, Shirai Tomokazu, Shimizu Hiroshi
• Format: Article
• Language: English
• Published: BMC 2007-06-01
• Series: Microbial Cell Factories
• Online Access: http://www.microbialcellfactories.com/content/6/1/19

<p>Abstract</p> <p>Background</p> <p><it>Corynebacterium glutamicum </it>has several anaplerotic pathways (anaplerosis), which are essential for the productions of amino acids, such as lysine and glutamate. It is still not clear how flux changes in anaplerotic pathways happen when glutamate production is induced by triggers, such as biotin depletion and the addition of the detergent material, Tween 40. In this study, we quantitatively analyzed which anaplerotic pathway flux most markedly changes the glutamate overproduction induced by Tween 40 addition.</p> <p>Results</p> <p>We performed a metabolic flux analysis (MFA) with [1-¹³C]- and [U-¹³C]-labeled glucose in the glutamate production phase of <it>C. glutamicum</it>, based on the analysis of the time courses of ¹³C incorporation into proteinogenic amino acids by gas chromatography-mass spectrometry (GC-MS). The flux from phosphoenolpyruvate (PEP) to oxaloacetate (Oxa) catalyzed by phosphoenolpyruvate carboxylase (PEPc) was active in the growth phase not producing glutamate, whereas that from pyruvate to Oxa catalyzed by pyruvate carboxylase (Pc) was inactive. In the glutamate overproduction phase induced by the addition of the detergent material Tween 40, the reaction catalyzed by Pc also became active in addition to the reaction catalyzed by PEPc.</p> <p>Conclusion</p> <p>It was clarified by a quantitative ¹³C MFA that the reaction catalyzed by Pc is most markedly increased, whereas other fluxes of PEPc and PEPck remain constant in the glutamate overproduction induced by Tween 40. This result is consistent with the previous results obtained in a comparative study on the glutamate productions of genetically recombinant Pc- and PEPc-overexpressing strains. The importance of a specific reaction in an anaplerotic pathway was elucidated at a metabolic level by MFA.</p>