Enzyme first used for nitrogen fixation

Options

A. Nitrogenase
B. Nitroreductase
C. Transferase
D. Transaminase

Answer

### Step-by-Step Solution:

1. **Understanding Nitrogen Fixation**:
- Nitrogen fixation is the process by which atmospheric nitrogen (N₂) is converted into ammonia (NH₃), which can be utilized by plants.

2. **Identifying the Enzymes**:
- The question provides four options: nitrogenase, nitro reductase, transferase, and transaminase. We need to identify which of these enzymes is primarily responsible for nitrogen fixation.

3. **Analyzing the Options**:
- **Nitrogenase**: This enzyme is specifically involved in the conversion of atmospheric nitrogen into ammonia. It is crucial for the nitrogen fixation process.
- **Nitro Reductase**: This enzyme is involved in the reduction of nitro compounds but is not directly related to nitrogen fixation.
- **Transferase**: This enzyme is responsible for transferring functional groups from one molecule to another, which does not apply to nitrogen fixation.
- **Transaminase**: This enzyme is involved in the transfer of amino groups but does not play a role in nitrogen fixation.

4. **Conclusion**:
- Since nitrogenase is the enzyme that catalyzes the conversion of atmospheric nitrogen to ammonia, it is the correct answer. Therefore, the answer to the question is **option A: Nitrogenase**.