title: The biosynthesis of tabtoxinine-beta-lactam. Use of specifically 13C-labeled glucose and 13C NMR spectroscopy to identify its biosynthetic precursors.
abstract: Tabtoxinine-beta-lactam, an irreversible inhibitor of glutamine synthetase is produced by several pathovars of Pseudomonas syringae. We have examined tabtoxinine-beta-lactam biosynthesis, an important and poorly characterized step in pathogenesis caused by this organism. We have identified the biosynthetic precursors of tabtoxinine-beta-lactam by incorporating 13C from specifically 13C-labeled D-glucose precursors and determining the labeling pattern using 13C NMR spectroscopy. Tabtoxinine-beta-lactam is generated by combining a 4-carbon fragment, a 2-carbon fragment, and a single carbon. The 4-carbon fragment arises from aspartic acid, and the 2-carbon unit is donated from carbons 2 and 3 of pyruvate. The 6-carbon backbone of tabtoxinine-beta-lactam arises from the condensation of fragments from aspartate and pyruvate, probably using reactions analogous to the initial steps in the pathway of lysine biosynthesis.
mesh_terms: D001224:Aspartic Acid / Q000378:metabolism; D001384:Azetidines / Q000096:biosynthesis*; D001385:Azetines / Q000096:biosynthesis*; D005947:Glucose / Q000378:metabolism; D005974:Glutamate-Ammonia Ligase / Q000037:antagonists & inhibitors; D008239:Lysine / Q000096:biosynthesis; D009682:Magnetic Resonance Spectroscopy; D008433:Mathematics; D011498:Protein Precursors / Q000032:analysis*; D011549:Pseudomonas / Q000378:metabolism; D011773:Pyruvates / Q000378:metabolism; D019289:Pyruvic Acid
chemical_list: D001384:Azetidines; D001385:Azetines; D011498:Protein Precursors; D011773:Pyruvates; D001224:Aspartic Acid; C051368:tabtoxinine beta-lactam; D019289:Pyruvic Acid; D005974:Glutamate-Ammonia Ligase; D005947:Glucose; D008239:Lysine