Which is not a protein ?

Options

A. a-amylase
B. Nitrogenase
C. Histidine kinase
D. Ribozyme.

Answer

To determine which option is not a protein, we need to analyze each of the given choices:

1. **Alpha amylase**: This is an enzyme that helps in the breakdown of starch into sugars. It is a protein that catalyzes this reaction.

2. **Nitrogenase**: This is an enzyme that catalyzes the conversion of nitrogen gas into ammonia. It is also a protein.

3. **Histidine**: This is an amino acid, which is a building block of proteins. While it is essential for protein synthesis, it is not a protein itself.

4. **Gynase**: This appears to be a misspelling or a less common term, but if it refers to an enzyme, it would typically be a protein.

5. **Ribozyme**: This is a type of RNA molecule that acts as a catalyst in biochemical reactions. Unlike proteins, ribozymes are made of RNA, not amino acids.

Based on this analysis, the correct answer is **ribozyme**, as it is not a protein but an RNA enzyme.

### Step-by-Step Solution:
1. **Identify the options**: The options provided are alpha amylase, nitrogenase, histidine, gynase, and ribozyme.

2. **Analyze each option**:
- Alpha amylase: Protein enzyme.
- Nitrogenase: Protein enzyme.
- Histidine: Amino acid, not a protein.
- Gynase: Likely a protein enzyme (assuming it's a variant of a known enzyme).
- Ribozyme: RNA enzyme, not a protein.

3. **Determine which is not a protein**: From the analysis, ribozyme is the only option that is not a protein.

4. **Conclude the answer**: The correct answer is ribozyme.