title: Comparative 13C metabolic flux analysis of pyruvate dehydrogenase complex-deficient, L-valine-producing Corynebacterium glutamicum.
abstract: 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 (13)C 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.
authors.affiliation: Institute of Bio and Geo Sciences, IBG-1, Biotechnology, Forschungszentrum Jülich, Jülich, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Bartek
authors.forename: Bastian
authors.initials: B
authors.lastname: Blombach
authors.forename: Siegmund
authors.initials: S
authors.lastname: Lang
authors.forename: Bernhard J
authors.initials: BJ
authors.lastname: Eikmanns
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Wiechert
authors.forename: Marco
authors.initials: M
authors.lastname: Oldiges
authors.forename: Katharina
authors.initials: K
authors.lastname: Nöh
authors.forename: Stephan
authors.initials: S
authors.lastname: Noack
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism; D002247:Carbon Isotopes / Q000378:metabolism*; D048230:Corynebacterium glutamicum / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D006019:Glycolysis; D009250:NADP Transhydrogenases / Q000235:genetics / Q000378:metabolism; D010427:Pentose Phosphate Pathway; D011768:Pyruvate Dehydrogenase Complex / Q000235:genetics*; D014633:Valine / Q000378:metabolism*
chemical_list: D002247:Carbon Isotopes; D029968:Escherichia coli Proteins; D011768:Pyruvate Dehydrogenase Complex; D002245:Carbon Dioxide; D009250:NADP Transhydrogenases; C556049:pntA protein, E coli; C556051:pntB protein, E coli; D014633:Valine