title: Effect of NH4+ on nitrogenase activity in nodule breis and bacteroides from Pisum sativum L.
abstract: Nodule breis and bacteroid preparations were made from Pisum sativum L. (cv. Trapper) inoculated with a single strain of Rhizobium leguminosarum. The detached nodules were triturated under helium flow. The resultant breis could support C2H2 reduction in N-Tris[hydroxymethyl]methyl-2-aminoethane-sulfonic acid buffer (Tes) without any additions for over an hour. NH4+ was found to inhibit C2H2 reduction and H2 evolution. The inhibition was not dependent on the counterion and was evident immediately after the addition of NH4+ to the reaction mixture. L-Methionine-D,L-sulfoximine, added to inhibit assimilation of NH4+, had no effect on the inhibition. Addition of pyruvate enhanced the rate of C2H2 reduction in breis and partially overcame the inhibition of NH4+. Pyruvate was found necessary for measurable activity in bacteroid preparations. When ATP and an ATP-generating system were used in breis the effect of NH4+ was not observed.
mesh_terms: D000114:Acetylene / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000643:Ammonium Chloride / Q000494:pharmacology*; D007887:Fabaceae; D006859:Hydrogen / Q000378:metabolism; D007700:Kinetics; D009591:Nitrogenase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D010084:Oxidation-Reduction; D010944:Plants / Q000201:enzymology*; D010946:Plants, Medicinal; D012231:Rhizobium / Q000201:enzymology*
chemical_list: D000643:Ammonium Chloride; D006859:Hydrogen; D000255:Adenosine Triphosphate; D009591:Nitrogenase; D000114:Acetylene