title: Pyrophosphate as a central energy carrier in the hydrogen-producing extremely thermophilic Caldicellulosiruptor saccharolyticus.
abstract: The role of inorganic pyrophosphate (PPi) as an energy carrier in the central metabolism of the extremely thermophilic bacterium Caldicellulosiruptor saccharolyticus was investigated. In agreement with its annotated genome sequence, cell extracts were shown to exhibit PPi-dependent phosphofructokinase and pyruvate phosphate dikinase activity. In addition, membrane-bound pyrophosphatase activity was demonstrated, while no significant cytosolic pyrophosphatase activity was detected. During the exponential growth phase, high PPi levels (approximately 4 +/- 2 mM) and relatively low ATP levels (0.43 +/- 0.07 mM) were found, and the PPi/ATP ratio decreased 13-fold when the cells entered the stationary phase. Pyruvate kinase activity appeared to be allosterically affected by PPi. Altogether, these findings suggest an important role for PPi in the central energy metabolism of C. saccharolyticus.
authors.affiliation: Laboratory of Microbiology, Wageningen UR, Wageningen, The Netherlands.
authors.forename: Abraham A M
authors.initials: AA
authors.lastname: Bielen
authors.forename: Karin
authors.initials: K
authors.lastname: Willquist
authors.forename: Jakob
authors.initials: J
authors.lastname: Engman
authors.forename: John
authors.initials: J
authors.lastname: van der Oost
authors.forename: Ed W J
authors.initials: EW
authors.lastname: van Niel
authors.forename: Servé W M
authors.initials: SW
authors.lastname: Kengen
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D011756:Diphosphates / Q000378:metabolism*; D004734:Energy Metabolism; D006094:Gram-Positive Bacteria / Q000254:growth & development / Q000378:metabolism*; D006859:Hydrogen / Q000378:metabolism*; D025221:Phosphofructokinases / Q000378:metabolism; D011755:Pyrophosphatases / Q000378:metabolism; D011772:Pyruvate, Orthophosphate Dikinase / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D011756:Diphosphates; D006859:Hydrogen; D000255:Adenosine Triphosphate; D025221:Phosphofructokinases; D011772:Pyruvate, Orthophosphate Dikinase; D011755:Pyrophosphatases