Oxidation-reduction reactions nitrogenase reaction

Nitrogenase catalyzes the reduction of a number of substrates in addition to N2 and H+. Acetylene is reduced to ethylene, and nitrous oxide to dinitrogen, while azide undergoes reduction to N2 and NH3. In the last two cases the product N2 is not reduced further, implying that it is not in the correct binding position for reduction. The presence of multiple sites on the MoFe protein suggested by this observation is also supported by the non-competitive nature of the inhibition shown by some of these compounds. The reduction of acetylene has been used as a marker reaction for nitrogenase activity. 

The rate-limiting step of nitrogenase is the dissociation of the reduced MoFe protein from the oxidized Fe protein and has a rate constant k = 6.4 0.8 sec-1. An implicit assumption in the multistep mechanism shown in Figure 13 is that the three elementary reactions coupling each state of the MoFe protein are unperturbed by the reduction level of the large protein. This assumption has been verified for the species E0 and ) [73],... 

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