Abstract
As the only enzyme currently known to reduce dinitrogen (N2) to ammonia (NH3), nitrogenase is of significant interest for bio-inspired catalyst design and for new biotechnologies aiming to produce NH3 from N2. In order to reduce N2, nitrogenase must also hydrolyze at least 16 equivalents of adenosine triphosphate (MgATP), representing the consumption of a significant quantity of energy available to biological systems. Here, we review natural and engineered electron transfer pathways to nitrogenase, including strategies to redirect or redistribute electron flow in vivo towards NH3 production. Further, we also review strategies to artificially reduce nitrogenase in vitro, where MgATP hydrolysis is necessary for turnover, in addition to strategies that are capable of bypassing the requirement of MgATP hydrolysis to achieve MgATP-independent N2 reduction.
Highlights
Introduction to NitrogenaseAmmonia (NH3 ) is an important commodity for agricultural and chemical industries that is currently produced at over 150 million tons per year [1,2]
H2, NADH, and KBH4 have been employed to transfer electrons to methyl viologen (MV) prior to catalysis by nitrogenase, in all of the reported cases the oxidation of MV by nitrogenase cannot be followed, since the oxidized MV is regenerated in these assays [146,147]
While the authors noted that N2 fixation was not observed, the 2e− -reduction of hydrazine (N2 H4 ) to NH3 was observed; further, a ß-Y98H MoFe protein mutant was required for the formation of significant quantities of NH3 when compared to blank/control experiments
Summary
Ammonia (NH3 ) is an important commodity for agricultural and chemical industries that is currently produced at over 150 million tons per year [1,2]. FeMo‐co via of events that transpire during this transient association is debated, electron transfer, 2MgATP the P cluster [9]. The reduction of N2 to NH3 requires 6e− , optimal N2 fixation by nitrogenase occurs after eight transient association events of the Fe protein (and the transfer of 8e− ): N2 + 8e− + 8H+ + 16MgATP → 2NH3 + H2 + 16MgADP + 16Pi (1). E4 state [8,10,21,22,23] By this model, the resting FeMo-co in its E0 state accumulates individual electrons and protons during each Fe protein association event in order to reach the E4 state at which N2 binds and undergoes subsequent reduction.
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