Part of active site of enzyme where substrate is held is known as

Options

A. Turnover number
B. Catalytic group
C. Activation site
D. Butterssing group.

Answer

To answer the question regarding the part of the active site of an enzyme where the substrate is held, we can break down the information as follows:

### Step-by-Step Solution:

1. **Understanding the Active Site**: The active site of an enzyme is a specific region where the substrate binds. This site is crucial for the enzyme's function.

2. **Identifying Groups in the Active Site**: According to Koshland's model, there are two main groups involved in the active site:
- **Group A (Butt Racing Group)**: This group serves to support the substrate. It is responsible for holding the substrate in place during the reaction.
- **Group B (Catalytic Group)**: This group is involved in the actual chemical reaction, facilitating the conversion of substrate into product.

3. **Function of the Groups**:
- The **Butt Racing Group** (Group A) ensures that the substrate is properly positioned for the reaction to occur.
- The **Catalytic Group** (Group B) forms weak bonds with the substrate, helping to lower the activation energy required for the reaction.

4. **Conformational Changes**: When the substrate binds to the Butt Racing Group, it induces conformational changes in the enzyme, which ultimately leads to the conversion of the substrate into the product.

5. **Conclusion**: Based on the information provided, the part of the active site of the enzyme where the substrate is held is known as the **Butt Racing Group**.

### Final Answer:
The part of the active site of the enzyme where the substrate is held is known as the **Butt Racing Group**.

---