Nitrogenase reduction by electron carriers: influence of redox potential on activity and the ATP/2e- ratio.
The variation with redox potential of nitrogenase activity and the ratio of ATP hydrolyzed per two electrons transferred were measured using two systems: the dithionite/bisulfite couple at pH 7.4; and H2, hydrogenase, and ferredoxin at pH 8.5. In both cases, the variation in nitrogenase activity with redox potential followed a theoretical Nernst plot for a two-electron process with an apparent midpoint potential of about -470 mV. The ratio ATP/2e- was about 4 under highly reducing conditions. However, above the apparent midpoint potential, the ratio ATP/2e- increased drastically, reaching values as high as 20. These data imply that a low redox potential must be maintained for efficient nitrogen fixation in vitro and in vivo.
D000255:Adenosine Triphosphate / Q000378:metabolism*; D055598:Chemical Phenomena; D002621:Chemistry; D004579:Electron Transport; D009591:Nitrogenase / Q000378:metabolism*; D010084:Oxidation-Reduction
D000255:Adenosine Triphosphate; D009591:Nitrogenase