title: Dependence of oxygen-tolerant nitrogenase activity on divalent cations in Azotobacter vinelandii.
abstract: Nitrogenase activity of washed Azotobacter vinelandii cells was enhanced by the addition of Ca2+ and Mg2+, and the enhancement increased with the O2 concentration. In assays provided with a level of O2 that was initially supraoptimal and inhibitory to nitrogenase activity, the addition of Ca2+ or Mg2+ affected both the maximum respiration rate (Vmax) of the cells and the apparent affinity [KS(O2)] of cell respiration for O2. Changes in these parameters correlated with changes in nitrogenase activity. Aeration-dependent increases in Vmax and KS(O2) were inhibited by rifampin and chloramphenicol and were also observed in ammonium-grown cultures.
authors.affiliation: Department of Botany, Iowa State University, Ames 50011.
authors.forename: J B
authors.initials: JB
authors.lastname: Peterson
mesh_terms: D000114:Acetylene / Q000378:metabolism; D016948:Azotobacter vinelandii / Q000378:metabolism*; D002118:Calcium / Q000494:pharmacology; D002413:Cations, Divalent / Q000494:pharmacology*; D002701:Chloramphenicol / Q000494:pharmacology; D008274:Magnesium / Q000494:pharmacology; D009586:Nitrogen Fixation; D009591:Nitrogenase / Q000187:drug effects / Q000378:metabolism*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000494:pharmacology; D010101:Oxygen Consumption / Q000187:drug effects; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D012293:Rifampin / Q000494:pharmacology
chemical_list: D002413:Cations, Divalent; D000644:Quaternary Ammonium Compounds; D002701:Chloramphenicol; D009591:Nitrogenase; D008274:Magnesium; D000114:Acetylene; D010100:Oxygen; D002118:Calcium; D012293:Rifampin