User:Aziz Hawsa/sandbox

The enzyme’s reduction equation reveals that a mole of H2 is produced per mole of N2. This phenomenon gives rise to the stoichiometric amount of electrons in the reactants side. Hydrogen is formed by nitrogenase when electrons and protons experience a cycle of accumulation and relaxation back to the rest state. However, with 25% of ATP (4 molecules) wasted during this process, it remains enigmatic as to why nitrogenase associates the evolution of H2 to the binding and reduction of N2.

Following crystallographic studies in the 90’s, FeMoco was determined to have a µ6-coordinated monoatomic light ligand. The presence of this ligand was believed to be particularly significant as it fills a void in the center of the FeMo cofactor and helps anchor the substrate to the binding site. It was not until 2011 that the identity of the interatrial atom was finally recognized via X-ray emission spectroscopy (XES) to be a carbide atom (C4-), however, the detailed role of this ligand remains unclear to this day. Another component to the MoFe protein is the P-cluster, which occupies the interface between the α/β-subunits. Similar to FeMoco, it is a Fe-S cluster with a hexacoordinated sulfide. Its function is to intercede the flow of electron from the homodimeric Fe protein to the active site of the heterotetrameric MoFe protein. Characteristically, the P-cluster is a combination of two [Fe4S4] cubanes that are bridged by µ6-sulfide.