Figure 19.

Comparison of the proposed reduction pathways of N₂ (left) and nitrite (right) by nitrogenase (M represents FeMo-cofactor). An intermediate, labeled E_n on N₂ pathway and E_m′ on nitrite pathway, has accumulated n or m [e⁻/H⁺]. (Boxed Region) Convergence of pathways for nitrite and N₂ reduction by nitrogenase, as discussed in the text. Within this region, boxed reactions of E₁ show the most direct routes by which N₂H₄ and NH₂OH join their respective pathways. Reproduced with permission from ref 193. Copyright 2014 American Chemical Society.