Question

Consider an enzymatic reaction that follows Michaelis-Menten kinetics. Let \( K_M \), \( S \), and \( V_{max} \) denote the Michaelis constant, substrate concentration, and maximum reaction rate, respectively. Which of the following statements is/are TRUE?

• A. For \( S \ll K_M \), the reaction is apparent first-order in \( S \).
• B. For \( S \gg K_M \), the reaction rate is nearly independent of \( S \).
• C. For \( S = K_M \), the rate of reaction equals \( V_{max} \).
• D. \( K_M \) is independent of the total enzyme concentration.

Hint:

It is essential to understand the underlying principles of Michaelis-Menten kinetics to effectively design experiments and analyze data in enzymology and other fields where enzyme catalysis is significant.

Answer 1

The Correct Option is A, B, D

Michaelis-Menten kinetics provides a framework for understanding how enzymatic reaction rates depend on substrate concentration. 
Step 1: Low Substrate Concentration (\( S \ll K_M \)):
At low substrate concentrations, the reaction rate equation simplifies to \( V = \frac{V_{max} \times S}{K_M} \), indicating a first-order dependence on \( S \) because the rate is linearly proportional to \( S \). 
Step 2: High Substrate Concentration (\( S \gg K_M \)):
When substrate concentrations are much higher than \( K_M \), the enzyme sites are nearly all saturated, making the rate approach \( V_{max} \) and becoming essentially independent of any additional increase in \( S \). 
Step 3: Independence of \( K_M \) from Enzyme Concentration:
\( K_M \) is a characteristic of the enzyme-substrate affinity and is not dependent on the total concentration of the enzyme. It reflects the substrate concentration at which the reaction rate is half of \( V_{max} \) and remains constant for a given enzyme and substrate under specific conditions.