Nitrogenase

Nitrogenase is an oxygen-sensitive enzyme complex that converts atmospheric nitrogen into ammonia. It occurs in certain bacteria and archaea and requires substantial energy and electron input.

Dinitrogen reduction: The chemical reduction of molecular nitrogen to ammonia or other nitrogen-containing products. Nitrogenase’s defining reaction converts N₂ into ammonia through multiple electron and proton transfers.
Nitrogenase iron protein: The ATP-binding component that supplies electrons to a nitrogenase catalytic component. This component partners with the catalytic protein to deliver electrons.
Vanadium nitrogenase: A nitrogen-fixing enzyme system that uses vanadium in its active-site cofactor instead of molybdenum. It can support nitrogen fixation when molybdenum is scarce.
Biological nitrogen fixation: The biological conversion of atmospheric nitrogen into ammonia by certain microorganisms. Nitrogenase is the enzyme system that performs this conversion.
Nitrogenase mechanism: The sequence of molecular events by which nitrogenase binds substrates and catalyzes their reduction. The precise intermediates and substrate-binding states remain active subjects of investigation.
Iron–molybdenum cofactor: The metal-sulfur cluster at nitrogenase’s active site where dinitrogen is reduced. This cofactor binds and reduces nitrogen during the catalytic cycle.
Nitrogenase catalytic component: The nitrogenase protein that contains the active-site metal cluster and catalyzes substrate reduction. It houses the metal center responsible for reducing nitrogen.
Iron-only nitrogenase: A nitrogenase system whose active-site cofactor contains iron but neither molybdenum nor vanadium. Its distinct cofactor provides an alternative to molybdenum- and vanadium-based systems.
Nitrogen cycle: The movement and transformation of nitrogen among organisms, soil, water, and atmosphere. Nitrogenase introduces biologically available nitrogen into the cycle.
Nitrogenase substrate scope: The range of molecules that nitrogenase can reduce besides molecular nitrogen. Understanding alternative substrates may reveal how its active site controls reactivity.

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