Question: 124: Which of the following protects nitrogenase inside the root nodule of a leguminous plant?
(1) Catalase
(2) leg haemoglobin
(3) Transaminase
(4) Glutamate dehydrogenase
Answer: Option (2)
Explanation:
Nitrogenase is the key enzyme responsible for biological nitrogen fixation in the root nodules of leguminous plants.
This enzyme is highly sensitive to oxygen and gets inactivated in the presence of free oxygen.
Leg haemoglobin is a pink-colored oxygen-binding protein present in the root nodules.
It maintains a very low concentration of free oxygen by binding oxygen tightly, thus protecting nitrogenase from oxygen damage.
At the same time, leg haemoglobin supplies sufficient oxygen for the respiration of nitrogen-fixing bacteria.
Catalase, transaminase, and glutamate dehydrogenase are metabolic enzymes but do not protect nitrogenase.
Hence, leg haemoglobin protects nitrogenase inside the root nodule.