According to IUB system, isomerases belong to which class?

Options

A. I
B. III
C. V
D. IV

Answer

To determine the class to which isomerases belong according to the IUB (International Union of Biochemistry) system, we can follow these steps:

1. **Understand the IUB System**: The IUB system categorizes enzymes into six main classes based on the type of reaction they catalyze.

2. **List the Six Classes**: The six classes of enzymes according to the IUB system are:
- Class 1: Oxidoreductases (dehydrogenases)
- Class 2: Transferases
- Class 3: Hydrolases
- Class 4: Lyases
- Class 5: Isomerases
- Class 6: Ligases

3. **Identify the Class for Isomerases**: From the list, we can see that isomerases are specifically mentioned as belonging to the fifth class.

4. **Conclusion**: Therefore, according to the IUB system, isomerases belong to the fifth class of enzymes.

### Final Answer:
Isomerases belong to the fifth class according to the IUB system.