The enzyme responsible for atmospheric nitrogen fixation is :

Step-by-step solution

Enzyme nitrogenase plays a key role in N ₂ fixations and remains active only during anaerobic condition. It is made up of two protein subunits : (i) non-heme iron protein or Fe-protein or dinitrogen reductase. (ii) Iron molybdenum protein or Mo-Fe protein or dinitrogenase.