title: Glycolysis without pyruvate kinase in Clostridium thermocellum.
abstract: The metabolism of Clostridium thermocellum is notable in that it assimilates sugar via the EMP pathway but does not possess a pyruvate kinase enzyme. In the wild type organism, there are three proposed pathways for conversion of phosphoenolpyruvate (PEP) to pyruvate, which differ in their cofactor usage. One path uses pyruvate phosphate dikinase (PPDK), another pathway uses the combined activities of PEP carboxykinase (PEPCK) and oxaloacetate decarboxylase (ODC). Yet another pathway, the malate shunt, uses the combined activities of PEPCK, malate dehydrogenase and malic enzyme. First we showed that there is no flux through the ODC pathway by enzyme assay. Flux through the remaining two pathways (PPDK and malate shunt) was determined by dynamic13C labeling. In the wild-type strain, the malate shunt accounts for about 33±2% of the flux to pyruvate, with the remainder via the PPDK pathway. Deletion of the ppdk gene resulted in a redirection of all pyruvate flux through the malate shunt. This provides the first direct evidence of the in-vivo function of the malate shunt.
authors.affiliation: Thayer School of Engineering, Dartmouth College, Hanover, NH 03755, USA; BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA. Electronic address: Daniel.G.Olson@Dartmouth.edu.
authors.forename: Daniel G
authors.initials: DG
authors.lastname: Olson
authors.affiliation: Institute of Molecular Systems Biology, ETH Zurich, Zurich, Switzerland.
authors.forename: Manuel
authors.initials: M
authors.lastname: Hörl
authors.affiliation: Institute of Molecular Systems Biology, ETH Zurich, Zurich, Switzerland.
authors.forename: Tobias
authors.initials: T
authors.lastname: Fuhrer
authors.affiliation: Thayer School of Engineering, Dartmouth College, Hanover, NH 03755, USA; BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA.
authors.forename: Jingxuan
authors.initials: J
authors.lastname: Cui
authors.affiliation: Thayer School of Engineering, Dartmouth College, Hanover, NH 03755, USA; BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA.
authors.forename: Jilai
authors.initials: J
authors.lastname: Zhou
authors.affiliation: Thayer School of Engineering, Dartmouth College, Hanover, NH 03755, USA; BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA.
authors.forename: Marybeth I
authors.initials: MI
authors.lastname: Maloney
authors.affiliation: Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Amador-Noguez
authors.affiliation: Thayer School of Engineering, Dartmouth College, Hanover, NH 03755, USA; BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA.
authors.forename: Liang
authors.initials: L
authors.lastname: Tian
authors.affiliation: Institute of Molecular Systems Biology, ETH Zurich, Zurich, Switzerland.
authors.forename: Uwe
authors.initials: U
authors.lastname: Sauer
authors.affiliation: Thayer School of Engineering, Dartmouth College, Hanover, NH 03755, USA; BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA. Electronic address: Lee.R.Lynd@Dartmouth.edu.
authors.forename: Lee R
authors.initials: LR
authors.lastname: Lynd
mesh_terms: D053898:Biosynthetic Pathways / Q000502:physiology*; D066241:Carbon-13 Magnetic Resonance Spectroscopy / Q000379:methods; D048013:Acetivibrio thermocellus / Q000502:physiology*; D005947:Glucose / Q000378:metabolism; D006019:Glycolysis / Q000502:physiology; D008293:Malates / Q000378:metabolism*; D064688:Metabolic Flux Analysis / Q000379:methods*; D053858:Metabolic Networks and Pathways / Q000502:physiology; D008954:Models, Biological; D010728:Phosphoenolpyruvate / Q000378:metabolism*; D011770:Pyruvate Kinase / Q000378:metabolism*; D019289:Pyruvic Acid / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D008293:Malates; D010728:Phosphoenolpyruvate; C030298:malic acid; D019289:Pyruvic Acid; D011770:Pyruvate Kinase; D005947:Glucose
keywords: (13)C flux analysis; Malate dehydrogenase; Malate shunt; Malic enzyme; Oxaloacetate decarboxylase; Pyruvate kinase