Question

Name the component that is mostly responsible for the specificity of the enzyme.

• A. Coenzyme
• B. Cofactor
• C. Apoenzyme
• D. Holoenzyme

Hint:

Remember: \(\text{Apoenzyme (inactive protein part)} + \text{Cofactor (non-protein helper)} = \text{Holoenzyme (active complex)}\). Substrate specificity resides in the apoenzyme.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Conjugated enzymes (holoenzymes) consist of a protein component and a non-protein component required for catalytic activity.
The functional properties of the enzyme are divided between these two components.

Step 2: Detailed Explanation:
Let us define the terminology used for conjugated enzymes:
- Holoenzyme: The complete, active complex containing both the protein and non-protein parts.
- Cofactor Coenzyme: The non-protein component, which can be a metal ion (cofactor) or a small organic molecule (coenzyme). These assist in chemical transformations, such as electron transfer or functional group mobilization.
- Apoenzyme: The purely proteinaceous portion of the enzyme.
The specificity of an enzyme refers to its ability to select and bind to a specific substrate.
This specificity is determined by the three-dimensional conformation, charge distribution, and geometric fit of the active site (often described by the lock-and-key or induced-fit models).
Since the active site is made of folded polypeptide chains belonging to the protein part, the apoenzyme is responsible for establishing substrate specificity.

Step 3: Final Answer:
The apoenzyme is the component mostly responsible for the specificity of the enzyme.