Biochemistry and physiology of nitrogen fixation

Biological dinitrogen fixation, the reduction of N₂ to NH₃, requires the enzyme nitrogenase, MgATP, a strongly reducing electron donor and an anaerobic environment. Reducing power for nitrogen fixation is generated by two particular mechanisms, while the mechanisms for protecting nitrogen fixation from oxygen show a greater diversity. Both the reduction and the protection aspects of nitrogen fixation, especially those of the legume root nodule, will be discussed.