Nitrogenase Assembly and CatalysisUpdate based on the original article by Yilin Hu, Benedikt Schmid & Markus W. Ribbe,Encyclopedia of Inorganic ChemistrySecond Edition, © 2005, John Wiley & Sons, Ltd

AbstractNitrogenases catalyze the reduction of N2to NH3as well as the reduction of alternative substrates such as H+, C2H2, and CO. The best characterized molybdenum nitrogenase (Mo‐nitrogenase) comprises two components: the Fe protein, which contains a [Fe4S4] cluster; and the MoFe protein, which contains two pairs of P‐cluster ([Fe8S7]) and FeMoco ([MoFe7S9C‐homocitrate]). The second best characterized nitrogenase is vanadium nitrogenase (V‐nitrogenase), which is highly homologous to Mo‐nitrogenase in structure and function, but far superior in reducing CO – an alternative substrate – to hydrocarbons.The assembly of Mo‐nitrogenase requires the participation of a number ofnitrogen‐fixing (nif) genes. The MoFe protein, the catalytic component of Mo‐nitrogenase, is synthesized through the ex situ assembly of FeMoco, the in situ assembly of P‐cluster, and the stepwise maturation of the two αβ‐halves of the MoFe protein. The catalysis of Mo‐nitrogenase involves the binding of MgATP to the reduced Fe protein, the complex formation of Fe protein with MoFe protein, and the interprotein electron transfer from the former to the latter concomitant with the hydrolysis of ATP. Once a sufficient amount of electrons is accumulated on the MoFe protein, substrate reduction takes place at its FeMoco site.