title: Nitrogenase of Klebsiella pneumoniae. Inhibition of acetylene reduction by magnesium ion explained by the formation of an inactive dimagnesium-adenosine triphophate complex.
abstract: Acetylene-reducing activity of purified nitrogenase from Klebsiella pneumoniae was studied over a range of ATP and Mg(2+) concentrations at 15 degrees C, pH7.8. Inhibition at Mg(2+) concentrations of 2.5-30mm was due to the formation of the inactive complex, Mg(2)ATP. At higher Mg(2+) concentrations an additional inhibitory effect was observed. The results were consistent with a MgATP complex being the active substrate with an apparent K(m)(MgATP)=0.4mm.
mesh_terms: D000114:Acetylene / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000494:pharmacology*; D007700:Kinetics; D007711:Klebsiella pneumoniae / Q000201:enzymology*; D008274:Magnesium / Q000494:pharmacology*; D009591:Nitrogenase / Q000037:antagonists & inhibitors*; D010084:Oxidation-Reduction; D013696:Temperature
chemical_list: D000255:Adenosine Triphosphate; D009591:Nitrogenase; D008274:Magnesium; D000114:Acetylene