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Journal of Bacteriology, December 2003, p. 7053-7067, Vol. 185, No. 24
0021-9193/03/$08.00+0     DOI: 10.1128/JB.185.24.7053-7067.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

Responses of the Central Metabolism in Escherichia coli to Phosphoglucose Isomerase and Glucose-6-Phosphate Dehydrogenase Knockouts{dagger}

Qiang Hua,1* Chen Yang,1 Tomoya Baba,1 Hirotada Mori,1,2 and Kazuyuki Shimizu1,3

Institute for Advanced Biosciences, Keio University, Tsuruoka 997-0017,1 Research and Education Center for Genetic Information, Nara Institute of Science and Technology, Ikoma 630-0101,2 Department of Biochemical Engineering & Science, Kyushu Institute of Technology, Iizuka 820-8502, Japan3

Received 10 June 2003/ Accepted 18 September 2003

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-13C]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.


* Corresponding author. Mailing address: Metabolome Unit, Institute for Advanced Biosciences, Keio University, Tsuruoka 997-0017, Japan. Phone: 81-235-29-0527. Fax: 81-235-29-0530. E-mail: huaq{at}sfc.keio.ac.jp.

{dagger} For a commentary on this article, see page 7031 in this issue.


Journal of Bacteriology, December 2003, p. 7053-7067, Vol. 185, No. 24
0021-9193/03/$08.00+0     DOI: 10.1128/JB.185.24.7053-7067.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.




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