Which one value is required for enzyme action ?

Options

A. Low `K_(m)`
B. High `K_(m)`
C. Low `K_(i)`
D. High `K_(i)`.

Answer

To determine which value is required for enzyme action, we need to understand the significance of the constants mentioned in the question: Km and Ki.

### Step-by-Step Solution:

1. **Understanding Km (Michaelis Constant)**:
- Km is a measure of the substrate concentration at which an enzyme operates at half its maximum velocity (Vmax).
- A low Km value indicates that the enzyme has a high affinity for its substrate, meaning it can effectively catalyze reactions even at low substrate concentrations.

2. **Understanding Ki (Inhibition Constant)**:
- Ki is the constant that reflects the potency of an inhibitor. It indicates how tightly an inhibitor binds to an enzyme.
- A low Ki value means that the inhibitor binds very tightly to the enzyme, which can significantly reduce the enzyme's activity and thus slow down the reaction rate.

3. **Analyzing the Options**:
- **Low Km**: This indicates high affinity for substrate, which is beneficial for enzyme action.
- **High Km**: This indicates low affinity for substrate, which is not favorable for enzyme action.
- **Low Ki**: This indicates strong binding of the inhibitor to the enzyme, which can reduce enzyme activity.
- **High Ki**: This indicates weak binding of the inhibitor, allowing for better enzyme activity.

4. **Conclusion**:
- For effective enzyme action, a low Km is desirable as it signifies high substrate affinity. However, the question specifically asks for the value required for enzyme action, which relates to the inhibitor's effect.
- A low Ki value is required for enzyme action because it implies that the enzyme is not inhibited strongly, allowing it to function effectively.

### Final Answer:
The value required for enzyme action is **low Ki**.