Enzymes, that catalyse removal of groups from substrates by mech anisms othe r than hydrolysis leaving double bonds, are :-

Options

A. Hydrolases
B. Ligases
C. Lyases
D. Isomerases

Answer

To solve the question regarding the enzymes that catalyze the removal of groups from substrates by mechanisms other than hydrolysis, leaving double bonds, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Enzyme Classification**: Enzymes are classified into six main categories based on the type of reaction they catalyze. The relevant classes for this question are:
- Oxidoreductases
- Transferases
- Hydrolases
- Lyases
- Isomerases
- Ligases

2. **Identifying the Mechanism**: The question specifies that we are looking for enzymes that remove groups without hydrolysis. Hydrolysis involves the addition of water to break bonds, which is not what we want in this case.

3. **Focusing on Lyases**: Lyases are enzymes that catalyze the removal of groups from substrates, resulting in the formation of double bonds. They do this by mechanisms other than hydrolysis. For example, they can remove a group (like CO2 or NH3) from a substrate, leading to the formation of a double bond.

4. **Excluding Other Classes**:
- **Oxidoreductases** (like dehydrogenases) involve oxidation-reduction reactions, often involving the removal of hydrogen or electrons.
- **Transferases** transfer functional groups from one molecule to another but do not necessarily form double bonds.
- **Hydrolases** involve hydrolysis, which we are excluding.
- **Isomerases** rearrange atoms within a molecule but do not typically remove groups.
- **Ligases** join two molecules together, which is not applicable here.

5. **Conclusion**: Based on the above analysis, the correct answer to the question is that the enzymes that catalyze the removal of groups from substrates by mechanisms other than hydrolysis, leaving double bonds, are **Lyases**.

### Final Answer:
**Lyases**