Figure 1.

Reaction and molecular mechanism of biological nitrogen fixation. A. General reaction of molecular nitrogen fixation B. Schematic structure and operation of the nitrogenase enzyme complex and subsequent metabolism of nitrogen. Electrons are transferred from reduced ferredoxin (or flavodoxin) via azoferredoxin to molybdoferredoxin. Each mol of fixed nitrogen requires 16 mol ATP hydrolyzed by the NifH protein. The NH₃ produced is utilised in the synthesis of glutamine or glutamate, respectively, for N-metabolism. NifJ: pyruvate flavodoxin/ferrodoxin oxidoreductase, NifF: Flavodoxin/Ferredoxin).