Which is not true for nitrogenase enzyme in root nodules in legumes?

Options

A. Synthesized by nif genes of Rhizobium
B. Site of reduction of ` N_ 2 ` into ` NH_ 3`
C. It is a Mo - Fe protein
D. Resistant to ` O_ 2 ` conc.

Answer

To determine which statement is not true regarding the nitrogenase enzyme in root nodules of legumes, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understanding Nitrogenase Enzyme**:
- Nitrogenase is an enzyme responsible for the conversion of atmospheric nitrogen (N2) into ammonia (NH3). This process is crucial for nitrogen fixation, particularly in leguminous plants that form symbiotic relationships with Rhizobium bacteria.

2. **Evaluating Each Statement**:
- **Option A: Synthesized by NIF genes of Rhizobium**:
- This statement is true. Nitrogenase is indeed synthesized by the NIF genes found in Rhizobium bacteria, which are present in the root nodules of legumes.

- **Option B: Site of reduction of N2 into NH3**:
- This statement is not true. The nitrogenase enzyme itself is not a site; rather, it is the enzyme that catalyzes the reaction. The site of reduction refers to the location where the reaction occurs, but the enzyme is not a site.

- **Option C: It is a MoFe protein**:
- This statement is true. Nitrogenase is a molybdenum-iron (MoFe) protein, which contains both molybdenum and iron as part of its structure.

- **Option D: Resistant to O2 concentration**:
- This statement is also true. Nitrogenase is sensitive to oxygen; high concentrations of oxygen can inhibit its activity. However, it is often described as being resistant to inactivation by oxygen, as it operates in low-oxygen environments such as root nodules.

3. **Conclusion**:
- Based on the evaluation, the statement that is not true regarding nitrogenase in root nodules of legumes is **Option B: Site of reduction of N2 into NH3**. This is because nitrogenase is an enzyme, not a site.

### Final Answer:
The statement that is not true for nitrogenase enzyme in root nodules in legumes is: **It is the site of reduction of N2 into NH3**.

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