Nitrogenase activity states

Thus, the hybrid cluster is a putative iron-sulfur redox catalyst. It is, however, a very uncommon cluster (perhaps only comparable to the nitrogenase active site) in two aspects (1) it is a hybrid cluster i.e., it contains intrinsic building blocks that are distinctly strange to iron-sulfur clusters and (2) it can exist in more than two (in fact, four [63]) oxidation states. 

But how does the FeMo-cofactor reduce N2 to ammonia, and where does the substrate N2 bind Several reaction pathways are discussed which employ a wide range of oxidation states of the Mo center [57,59,60]. Very little of the reactivity observed to date is likely to occiu at a nitrogenase active site. New insights in the speculative synthetic chemistry and the nitrogenase problem were reviewed recently. Note that without N2 as substrate, the enzyme spontaneously reduces protons to H2 [32]. 

Hitch (1971) studied the environmental factors affecting nitrogenase activity in lichens, and has reported diurnal and seasonal variation in Collema, Lichina, and Peltigera. When samples collected from the field in a desiccated state were wetted, nitrogenase activity started after lag periods of 60, 20, and 35 minutes, respectively. The thallus moisture contents, however, changed from the original level of 20% oven-dry weight to 200% within... 

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