Which of the following is required for the activity of nitrogenase?

Nitrogenase is an enzyme complex responsible for the biological reduction of atmospheric nitrogen to ammonia, a process known as nitrogen fixation. The activity of nitrogenase is critically dependent on the presence of the FeMo cofactor. This cofactor contains iron and molybdenum and is essential for the catalysis of nitrogen reduction. Its unique structure allows the enzyme to facilitate the reaction by stabilizing intermediates and enabling electron transfer, which is crucial for the conversion of nitrogen gas (N₂) into ammonia (NH₃).

The FeMo cofactor is embedded within the larger nitrogenase enzyme complex and underlies the biochemical mechanism that converts N₂ to ammonia, utilizing high-energy electrons typically provided by electron donors like ferredoxin. This cofactor's distinct electron-rich nature is pivotal in breaking the strong triple bond of the nitrogen molecule, thereby enabling the nitrogen fixation process.

While iron is necessary for the formation of the FeMo cofactor and is indeed a component of nitrogenase, relying on iron alone would be insufficient for nitrogenase activity. Magnesium ions and zinc ions, while they may play roles in other enzymatic reactions or structural configurations, are not directly involved in the catalytic mechanism of nitrogenase and therefore are not required for its activity.