106. Nitrogenase is a complex enzyme consisting of MoFe protein and Fe-protein. Which one of the
following statements regarding Nitrogenase enzyme is NOT correct?
1. It comprises of Component I and Component II
2. MoFe proteins are dinitrogenase reductases
3. Fe proteins are homodimer
4. MoFe proteins are heterotetramer

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Question:

Nitrogenase is a complex enzyme consisting of MoFe protein and Fe-protein. Which one of the following statements regarding Nitrogenase enzyme is NOT correct?

1. It comprises of Component I and Component II

2. MoFe proteins are dinitrogenase reductases

3. Fe proteins are homodimer

4. MoFe proteins are heterotetramer

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Correct Answer:

2. MoFe proteins are dinitrogenase reductases

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Explanation:

The nitrogenase enzyme plays a crucial role in biological nitrogen fixation, which is the process by which nitrogen gas (N₂) is converted into ammonia (NH₃). It consists of two major components: MoFe proteins and Fe proteins. Here’s a breakdown of the provided options:

1. It comprises of Component I and Component II:
   This statement is correct. The nitrogenase enzyme consists of two components: Component I (MoFe protein) and Component II (Fe protein). These components work together in the nitrogen fixation process.

2. MoFe proteins are dinitrogenase reductases:
   This statement is NOT correct. MoFe proteins are dinitrogenase (not dinitrogenase reductases). Dinitrogenase is responsible for the actual reduction of nitrogen to ammonia. The term “dinitrogenase reductase” is more accurately applied to the Fe-protein component, which donates electrons to the MoFe protein.

3. Fe proteins are homodimer:
   This statement is correct. Fe proteins (Component II) are homodimers, meaning they consist of two identical subunits. These subunits are involved in the electron transfer to the MoFe protein.

4. MoFe proteins are heterotetramer:
   This statement is correct. MoFe proteins (Component I) are heterotetramers, meaning they consist of four subunits made up of two types of proteins (alpha and beta). This structure is essential for the nitrogenase enzyme’s function in nitrogen fixation.

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Conclusion:

The correct answer is 2. MoFe proteins are dinitrogenase reductases, which is incorrect. MoFe proteins are dinitrogenase, not dinitrogenase reductases. The Fe-protein component of the nitrogenase enzyme is responsible for donating electrons, which is why it is referred to as dinitrogenase reductase.

Correct Answer: 2. MoFe proteins are dinitrogenase reductases