Step 1: Concept Overview:
The question requires identification of the key enzymes directly participating in biological nitrogen fixation.
Step 2: Detailed Explanation:
The conversion of atmospheric nitrogen (\(N_2\)) to ammonia (\(NH_3\)) is mediated by several enzymes.
Nitrogenase: This essential enzyme complex catalyzes the reduction of \(N_2\) to \(NH_3\). It is oxygen-sensitive and indispensable for nitrogen fixation.
Hydrogenase: Nitrogenase produces hydrogen gas (\(H_2\)) as a byproduct, consuming ATP and electrons. Uptake hydrogenase recycles \(H_2\) through oxidation, recovering lost energy and enhancing nitrogen fixation efficiency. Therefore, hydrogenase is a very important enzyme for improving the overall efficiency of nitrogen fixation.
Peptidase, Hexokinase, Dehydrogenase: While vital for general cellular metabolism (protein breakdown, glycolysis, respiration), these enzymes are not directly involved in nitrogen fixation.
Step 3: Conclusion:
Nitrogenase (for the primary reaction) and Hydrogenase (for improved efficiency) are the key enzymes in nitrogen fixation.