Nitrogenase is the enzyme used by some organisms to fix atmospheric nitrogen gas. It is only known family of enzymes which accomplishes this process.

Nitrogenase is the enzyme used by some organisms to fix atmospheric nitrogen gas. It is only known family of enzymes which accomplishes this process. Dinitrogen has a triple bond between nitrogen aoms. Nitrogenase thus breaks the triple bond by getting electron donors for each of the three bonds, and bonds the nitrogen to hydrogen atoms. The process is complex because each bond Is broken individually. Nitrogenase requires both the MoFe protein and ATP which supplies the energy. Nitrogenase bonds each atom of nitrogen to three atoms of hydrogen to form ammonia or NH3 each time nitrogenase associates with a second protin and each cycle transfers one electron from an electron donor which is enough to break one of the nitrogen chemical bonds. The enzyme is composed of the heterotetrameric MoFe protein that is transiently associated with the homodimeric Fe protein. Nitrogenase is supplied reducing power when it associates with the reduced, nucleotide-bound homodimeric Fe rotein.