Michaelis - Menten constant `(K_(m))` of an enzyme is substrate concentration at which the reaction attains

Options

A. its maximum velocity
B. half its maximum velocity
C. double its maximum velocity
D. its normal velocity

Answer

To solve the question regarding the Michaelis-Menten constant (Km) of an enzyme, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Km**: The Michaelis-Menten constant (Km) is a key parameter in enzyme kinetics. It is defined as the substrate concentration at which the reaction rate is half of its maximum velocity (Vmax).

2. **Identifying Vmax**: Vmax is the maximum rate of the reaction when the enzyme is fully saturated with the substrate. At this point, all active sites of the enzyme molecules are occupied by the substrate.

3. **Defining Half of Vmax**: Half of the maximum velocity (Vmax/2) is the reaction rate at which the enzyme is operating at 50% efficiency. This is the point where the substrate concentration is equal to Km.

4. **Conclusion**: Based on the definition of Km, we can conclude that Km is the substrate concentration at which the reaction attains half of its maximum velocity (Vmax/2).

5. **Selecting the Correct Option**: Given the options:
- a) its maximum velocity
- b) half of its maximum velocity
- c) double its maximum velocity
- d) it equals to its normal velocity

The correct answer is **b) half of its maximum velocity**.

### Final Answer:
The Michaelis-Menten constant (Km) of an enzyme is the substrate concentration at which the reaction attains **half of its maximum velocity**.

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