A working combination of an apoenzyme and a co - enzyme is termed as

Options

A. prosthetic group
B. enzyme - substrate complex
C. holoenzyme
D. enzyme product complex

Answer

To answer the question "A working combination of an apoenzyme and a coenzyme is termed as," we can follow these steps:

### Step 1: Understand the Definitions
- **Apoenzyme**: This is the protein part of an enzyme that is inactive on its own.
- **Coenzyme**: This is a non-protein molecule that binds to the apoenzyme and is necessary for the enzyme's activity.

### Step 2: Identify the Combination
- When an apoenzyme combines with a coenzyme, it forms a complete and active enzyme. This combination is crucial for the enzyme's function.

### Step 3: Identify the Correct Term
- The term that describes the working combination of an apoenzyme and a coenzyme is **holoenzyme**. A holoenzyme is the active form of the enzyme that can catalyze reactions.

### Step 4: Evaluate the Options
- **Prosthetic Group**: This refers to a cofactor that is tightly bound to an enzyme, not the combination of an apoenzyme and a coenzyme.
- **Enzyme-Substrate Complex**: This is a temporary complex formed when an enzyme binds to its substrate, not the combination of an apoenzyme and a coenzyme.
- **Polypeptide Enzyme**: This term is not commonly used in this context.
- **Enzyme-Product Complex**: This is formed after the enzyme has acted on the substrate, not the combination of apoenzyme and coenzyme.

### Conclusion
The correct answer to the question is that the working combination of an apoenzyme and a coenzyme is termed as **holoenzyme**.

---