Enzymes which possess an additional site other than active

Options

A. apoenzymes
B. conjugated enzymes
C. holoenzymes
D. allosteric enzymes

Answer

To solve the question regarding enzymes that possess an additional site other than the active site, we can analyze the options provided:

1. **Apoenzyme**: This term refers to the protein component of an enzyme that is inactive without its cofactor. It does not refer to an enzyme with an additional site.

2. **Conjugated enzyme**: This type of enzyme contains prosthetic groups or conjugated groups. While it may have additional components, it does not specifically indicate an additional site for regulatory purposes.

3. **Holoenzyme**: This is the complete, active form of an enzyme that includes both the apoenzyme and its cofactor. It does not specifically denote an additional regulatory site.

4. **Allosteric enzyme**: These enzymes have an additional site known as the allosteric site, which is distinct from the active site. This site is involved in the regulation of the enzyme's activity, allowing for the binding of regulatory molecules that can enhance or inhibit enzyme function.

Based on this analysis, the correct answer is:

**Allosteric enzyme**.

### Step-by-Step Solution:
1. **Identify the question**: The question asks for enzymes that have an additional site other than the active site.

2. **Evaluate the options**:
- **Apoenzyme**: Not applicable, as it refers to the inactive protein part.
- **Conjugated enzyme**: Contains prosthetic groups but does not imply an additional regulatory site.
- **Holoenzyme**: Represents the complete enzyme but does not indicate an additional site.
- **Allosteric enzyme**: Has an additional regulatory site, making it the correct choice.

3. **Select the correct answer**: The answer is **Allosteric enzyme** because it specifically has an additional site (allosteric site) that regulates enzyme activity.