State the chemical nature and role of nitrogease enzyme in nitrogen fixation by leguminous plants.How is it prevented from destruction by oxygen in root nodules?

Dear student, 

Leguminous plants have the special characteristic of showing symbiotic association with some microbes(e.g-Rhizobium, Frankia, etc) and thus help in nitrogen fixation(reduction of atmospheric nitrogen to ammonia) in the environment.The enzyme required for this nitrogen fixation is nitrogenase, and this is found only in nitrogen-fixing bacteria.

The chemical nature of the enzyme : The nitrogenase molecule  has two iron containing proteins bonded to a molybdenum or iron protein on both the ends.

Now, since the nitrogenase enzyme is inhibited in the presence of oxygen, the root nodules of leguminous plants have a characteristic adaptation that helps in ensuring that the enzyme is protected from the destruction of oxygen. The root nodules thus contain a pigment called leg haemoglobin, that acts as an oxygen scavenger, and hence it  protects the oxygen-sensitive enzyme nitrogenase.


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