title: 31P NMR studies of energy metabolism in xanthosine-5'-monophosphate overproducing Corynebacterium ammoniagenes.
abstract: Corynebacterium ammoniagenes is an overproducer of xanthosine-5'-monophosphate (XMP) by consuming either glcose (glc) or glutamic acid (glu). Its energy metabolism was studied in vivo using 31P NMR spectroscopy coupled with a circulating fermentation system (CFS). CFS enabled us to validate directly the cellular dependency on carbon sources and changes in biomolecules produced according to alterations in the cellular energetic status. For the most efficient XMP production, the glutamic acid and glcose molar ratios (glu/glc) in the medium were adjusted to a molar ratio of 0.31. The 31P NMR illustrated the two distinct phases of the cellular energetic status due to the availability of the substrates from the medium. In the earlier phase, both glc and glu were utilized, resulting in average ATP and ADP concentrations in cells of 0.50 +/- 0.17 micro mol.g-1 of dry cell weight (DCW) and an undetermined level, respectively. The ADP concentration in the later phase increased to 2.15 +/- 1.30 micro mol.g-1 of DCW, while the ATP concentration decreased to an undetectable level in association with a remarkable decrease in XMP production. This decrease in the XMP-producing ability was associated with an increase in production of the by-product hypoxanthine. Because glu was found to be consumed completely during the earlier phase, glc was the only available substrate in the later phases. These findings by in vivo NMR indicate that changes in the carbon metabolism profoundly affect XMP production by C. ammoniagenes.
authors.affiliation: Fermentation & Biotechnology Laboratories and Central Research Laboratories, Ajinomoto Co., Inc., Kawasaki-ku, Kawasaki, Kanagawa, Japan. yasushi_noguchi@aijonomoto.com
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Noguchi
authors.forename: Nobuhisa
authors.initials: N
authors.lastname: Shimba
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Kawahara
authors.forename: Ei-ichiro
authors.initials: E
authors.lastname: Suzuki
authors.forename: Shinichi
authors.initials: S
authors.lastname: Sugimoto
mesh_terms: D000227:Adenine Nucleotides / Q000378:metabolism*; D003352:Corynebacterium / Q000378:metabolism*; D004734:Energy Metabolism; D004926:Escherichia coli / Q000378:metabolism; D018698:Glutamic Acid / Q000494:pharmacology; D019271:Hypoxanthine / Q000378:metabolism; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D010758:Phosphorus; D012265:Ribonucleotides / Q000096:biosynthesis*; D019820:Xanthine
chemical_list: D000227:Adenine Nucleotides; D012265:Ribonucleotides; D019820:Xanthine; D010758:Phosphorus; D019271:Hypoxanthine; D018698:Glutamic Acid; C011141:xanthosine monophosphate