Non-protein part of enzyme is known as

Options

A. Apoenzyme
B. Cofactor
C. Inorganic catalyst
D. Active site

Answer

### Step-by-Step Solution:

1. **Understanding the Structure of Enzymes**: Enzymes are biological catalysts that speed up chemical reactions in living organisms. They are typically composed of two main parts: a protein part and a non-protein part.

2. **Identifying the Protein Part**: The protein part of the enzyme is referred to as the **apoenzyme**. This part is responsible for the enzyme's structure and function.

3. **Identifying the Non-Protein Part**: The non-protein part of the enzyme is known as the **cofactor**. Cofactors can be metal ions or organic molecules that assist in the enzyme's activity.

4. **Function of Cofactors**: Cofactors are essential for the enzymatic activity, as they help in the proper functioning of the enzyme. They can be classified into two categories:
- **Coenzymes**: Organic molecules that are loosely attached to the enzyme.
- **Metal ions**: Inorganic molecules that can be tightly or loosely bound to the enzyme.

5. **Formation of Holoenzyme**: When the apoenzyme (the protein part) combines with its cofactor (the non-protein part), they form a complete and active enzyme known as a **holoenzyme**.

6. **Conclusion**: Therefore, the non-protein part of the enzyme is known as the **cofactor**.

### Final Answer:
The non-protein part of an enzyme is known as a **cofactor**.

---