title: Metabolic flux analysis of pykF gene knockout Escherichia coli based on 13C-labeling experiments together with measurements of enzyme activities and intracellular metabolite concentrations.
abstract: Metabolic flux analysis based on 13C-labeling experiments followed by the measurement of intracellular isotope distribution using both 2D NMR and GC-MS was carried out to investigate the effect of pyruvate kinase (pyk) gene knockout on the metabolism of Escherichia coli in continuous culture. In addition, the activities of 16 enzymes, and the concentrations of 5 intracellular metabolites, were measured as a function of time in batch culture as well as continuous culture. It was found that flux through phosphoenol pyruvate carboxylase and malic enzyme were up-regulated in the pykF- mutant as compared with the wild type, and acetate formation was significantly reduced in the mutant. In addition, flux through the phosphofructose kinase pathway was reduced and that through the oxidative pentose phosphate (PP) pathway increased in the mutant. This was evidenced by the corresponding enzyme activities, and the increase in the concentrations of phosphoenol pyruvate, glucose-6-phosphate and 6-phosphogluconate, etc. It was also found for continuous cultivation that the enzyme activities of the oxidative PP and Entner-Doudoroff pathways increased as the dilution rate increased for the pykF- mutant. To clarify the metabolism quantitatively, it was found to be quite important to integrate the information on intracellular metabolic flux distribution, enzyme activities and intracellular metabolite concentrations.
authors.affiliation: Department of Biochemical Engineering and Science, Kyushu Institute of Technology, Iizuka, 820-8502 Fukuoka, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Al Zaid Siddiquee
authors.forename: M J
authors.initials: MJ
authors.lastname: Arauzo-Bravo
authors.forename: K
authors.initials: K
authors.lastname: Shimizu
mesh_terms: D019342:Acetic Acid / Q000378:metabolism; D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000096:biosynthesis; D002241:Carbohydrates / Q000032:analysis; D002245:Carbon Dioxide / Q000378:metabolism; D003593:Cytoplasm / Q000737:chemistry; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D008401:Gas Chromatography-Mass Spectrometry; D017353:Gene Deletion; D005798:Genes, Bacterial; D019298:Glucose-6-Phosphate / Q000032:analysis; D006019:Glycolysis; D009682:Magnetic Resonance Spectroscopy; D008291:Malate Dehydrogenase / Q000502:physiology; D010427:Pentose Phosphate Pathway / Q000502:physiology; D010728:Phosphoenolpyruvate / Q000378:metabolism; D010730:Phosphoenolpyruvate Carboxylase / Q000502:physiology; D011770:Pyruvate Kinase / Q000235:genetics* / Q000378:metabolism*; D019289:Pyruvic Acid / Q000378:metabolism
chemical_list: D002241:Carbohydrates; D002245:Carbon Dioxide; D019298:Glucose-6-Phosphate; D000244:Adenosine Diphosphate; D010728:Phosphoenolpyruvate; D019289:Pyruvic Acid; D000255:Adenosine Triphosphate; D008291:Malate Dehydrogenase; D011770:Pyruvate Kinase; D010730:Phosphoenolpyruvate Carboxylase; D019342:Acetic Acid