Enzymes which breakdown compounds without using `H_(2) O` are called.

Options

A. lyases
B. ligases
C. hydroleases
D. proteases

Answer

To solve the question regarding enzymes that break down compounds without using water, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Enzymes**: Enzymes are biological catalysts that speed up chemical reactions in living organisms. They can be classified into different categories based on their functions.

2. **Identifying the Type of Enzyme**: The question specifically asks for enzymes that break down compounds without the involvement of water (H₂O).

3. **Defining Lyases**: The enzymes that fit this description are called **lyases**. Lyases are responsible for breaking chemical bonds by means other than hydrolysis (which involves water) or oxidation.

4. **Mechanism of Lyases**: Lyases typically remove groups from substrates to form double bonds or add groups to double bonds. For example, if a substrate has two groups (X and Y), a lyase can remove these groups and form a double bond in the substrate.

5. **Differentiating from Other Enzymes**: It's important to note that other types of enzymes exist, such as:
- **Hydrolases**: These enzymes catalyze reactions that involve the addition of water to break down compounds (e.g., breaking down esters or peptides).
- **Ligases**: These enzymes join two molecules together, often requiring energy (like ATP), but they do not break down compounds.

6. **Conclusion**: Based on the definition and function of the enzymes, the answer to the question is that the enzymes which break down compounds without using water are called **lyases**.

### Final Answer:
**Lyases**

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