title: Electron transport to nitrogenase. Purification and characterization of pyruvate:flavodoxin oxidoreductase. The nifJ gene product.
abstract: Pyruvate:flavodoxin oxidoreductase, the nifJ gene product of Klebsiella pneumoniae, was purified to homogeneity. Pyruvate:flavodoxin oxidoreductase, flavodoxin, and nitrogenase components I and II are the only proteins required for pyruvate-coupled nitrogenase activity. The physiological source of electrons to nitrogenase in K. pneumoniae is pyruvate. Flavodoxin from Azotobacter vinelandii was only one-third as effective as K. pneumoniae flavodoxin in transferring electrons from pyruvate:flavodoxin oxidoreductase to Azotobacter and Klebsiella nitrogenases. Ferredoxins from aerobic, anaerobic and photosynthetic nitrogen-fixing organisms, as well as benzyl viologen and methyl viologen, were ineffective in coupling pyruvate oxidation to nitrogenase activity. One mol each of acetyl-CoA, CO2, and ethylene are formed by pyruvate-supported acetylene reduction. The enzyme contains 8.0 +/- 0.6 mol of iron and 6.6 +/- 0.2 mol of acid-labile sulfide per mol of protein (Mr = 240,000). Pyruvate:flavodoxin oxidoreductase is irreversibly inactivated by air.
mesh_terms: D004579:Electron Transport; D005796:Genes; D005798:Genes, Bacterial; D007658:Ketone Oxidoreductases / Q000235:genetics* / Q000302:isolation & purification; D007700:Kinetics; D007711:Klebsiella pneumoniae / Q000201:enzymology*; D009591:Nitrogenase / Q000235:genetics*; D010084:Oxidation-Reduction; D013053:Spectrophotometry
chemical_list: D009591:Nitrogenase; D007658:Ketone Oxidoreductases; C039443:pyruvate-flavodoxin oxidoreductase