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Nitrogenase Catalysis & Assembly

  1. Yilin Hu1,
  2. Benedikt Schmid2,
  3. Markus W. Ribbe1

Published Online: 15 MAR 2006

DOI: 10.1002/0470862106.ia159

Encyclopedia of Inorganic Chemistry

Encyclopedia of Inorganic Chemistry

How to Cite

Hu, Y., Schmid, B. and Ribbe, M. W. 2006. Nitrogenase Catalysis & Assembly . Encyclopedia of Inorganic Chemistry. .

Author Information

  1. 1

    University of California-Irvine, Irvine, CA, USA

  2. 2

    University of Erlangen-Nürnberg, Erlangen, Germany

Publication History

  1. Published Online: 15 MAR 2006


Nitrogenases are metalloenzymes that catalyze biological N2 fixation, in which dinitrogen is reduced to ammonia. The best-characterized molybdenum nitrogenase is composed of the iron (Fe) protein that contains a [4Fe–4S] cluster and the molybdenum–iron (MoFe) protein that contains an [8Fe–7S] cluster (P cluster) and a [Mo–7Fe–9S–homocitrate] cluster (FeMo cofactor).

The catalysis of molybdenum nitrogenase occurs in a series of steps. First, the reduced Fe protein binds 2MgATP, undergoes a conformational change, and forms a complex with the MoFe protein. Then, coupled with the hydrolysis of 2MgATP, one electron is transferred from the Fe protein to the MoFe protein within the complex. This is followed by complex dissociation, which allows the enzyme to start the next cycle of electron transfer. Once a sufficient amount of electrons is accumulated on the MoFe protein, substrate reduction takes place.

The assembly of the molybdenum nitrogenase Fe protein involves the nifH and at least the nifS, nifU, and nifM gene products that are implicated in the [4Fe–4S] cluster assembly, while the assembly of the MoFe protein requires at least 15 nif gene products and involves the biosynthesis and insertion of the FeMo cofactor into the MoFe protein.


  • Azotobacter vinelandii;
  • nitrogenase assembly;
  • nitrogenase catalysis;
  • molybdenum nitrogenase;
  • vanadium nitrogenase;
  • iron-only nitrogenase;
  • MoFe protein;
  • Fe protein;
  • FeMo cofactor;
  • P cluster