title: Effect of chelating agents on hydrogenase in Azotobacter chroococcum. Evidence that nickel is required for hydrogenase synthesis.
abstract: The chelating agents EDTA, o-phenanthroline, nitrilotriacetic acid (NTA), ethylenediamine-bis(o-hydroxyphenylacetic acid) (EDDA) or dimethylglyoxime prevented the expression of hydrogenase activity in batch cultures of nitrogen-fixing Azotobacter chroococcum, but did not inhibit preformed enzyme. The inhibition was reversed either by adding a mixture of trace elements (Cu2+, Mn2+, Zn2+, Co2+) or Ni2+ or, to a lesser degree, Co2+ alone. Ni2+ or Ni2+ + Fe2+ also enhanced the rate of hydrogenase derepression in A. chroococcum in the absence of any added chelator, if the medium was first extracted with 8-hydroxyquinoline. A. chroococcum accumulated 63Ni2+ by an energy-independent mechanism. Both, Ni2+ uptake and hydrogenase synthesis were equally inhibited by either NTA, EDTA, EDDA or dimethylglyoxime. The evidence suggests a role for Ni2+ in hydrogenase synthesis.
mesh_terms: D001395:Azotobacter / Q000187:drug effects / Q000201:enzymology*; D002614:Chelating Agents / Q000494:pharmacology*; D006864:Hydrogenase; D007501:Iron / Q000494:pharmacology; D009532:Nickel / Q000494:pharmacology*; D009571:Nitrilotriacetic Acid / Q000494:pharmacology; D010088:Oxidoreductases / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D014131:Trace Elements / Q000494:pharmacology
chemical_list: D002614:Chelating Agents; D014131:Trace Elements; D009532:Nickel; D007501:Iron; D010088:Oxidoreductases; D006864:Hydrogenase; D009571:Nitrilotriacetic Acid