One of the following is without coenzyme activity

Options

A. Vitamin E
B. Thiamine
C. Biotin
D. Riboflavin.

Answer

To solve the question "One of the following is without coenzyme activity," we need to analyze each of the provided options to determine which one does not function as a coenzyme.

### Step-by-Step Solution:

1. **Identify the Options**: The options given are:
- A) Vitamin E
- B) Thiamine
- C) Biotin
- D) Riboflavin

2. **Analyze Vitamin E**:
- Vitamin E is a fat-soluble vitamin known for its antioxidant properties.
- It does not have any reported coenzyme activity.
- Therefore, Vitamin E is a candidate for the correct answer.

3. **Analyze Thiamine**:
- Thiamine (Vitamin B1) is a water-soluble vitamin.
- It acts as a coenzyme in the form of thiamine pyrophosphate.
- It is involved in several metabolic reactions, such as those catalyzed by pyruvate dehydrogenase and pyruvate decarboxylase.
- Thus, Thiamine has coenzyme activity.

4. **Analyze Biotin**:
- Biotin is also a water-soluble vitamin.
- It acts as a coenzyme for various carboxylase enzymes (e.g., acetyl-CoA carboxylase, pyruvate carboxylase).
- Therefore, Biotin has coenzyme activity.

5. **Analyze Riboflavin**:
- Riboflavin (Vitamin B2) is another water-soluble vitamin.
- It acts as a coenzyme in the form of flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD).
- Thus, Riboflavin also has coenzyme activity.

6. **Conclusion**:
- After analyzing all options, we find that:
- Vitamin E does not have coenzyme activity.
- Thiamine, Biotin, and Riboflavin all have coenzyme activity.
- Therefore, the correct answer is **Vitamin E**.

### Final Answer:
**Vitamin E** is the option that is without coenzyme activity.