title: Evidence for direct repression of nitrogenase by ammonia in the cyanobacterium Anabaena cylindrica.
abstract: The nitrogenase activity of the cyanobacterium Anabaena cylindrica was repressed upon addition of ammonium salts after preincubation in the presence of a concentration of L-methionine-DL-sulfoximine sufficient to totally inhibit glutamine synthetase. Repression was also observed when urea was added to cells in the presence of the glutamine synthetase inhibitor. Measurements of ammonia concentrations were made in each case and provided evidence that ammonia itself is a primary regulator of nitrogenase levels in A. cylindrica.
authors.forename: A H
authors.initials: AH
authors.lastname: Mackerras
authors.forename: G D
authors.initials: GD
authors.lastname: Smith
mesh_terms: D000641:Ammonia / Q000494:pharmacology*; D000458:Cyanobacteria / Q000201:enzymology*; D004794:Enzyme Repression / Q000187:drug effects; D008717:Methionine Sulfoximine / Q000494:pharmacology; D009591:Nitrogenase / Q000096:biosynthesis / Q000378:metabolism*; D014508:Urea / Q000494:pharmacology
chemical_list: D008717:Methionine Sulfoximine; D000641:Ammonia; D014508:Urea; D009591:Nitrogenase