Question

Consider the following enzyme catalyzed reaction:

where \( E \) is enzyme, \( S \) is substrate, \( ES \) is enzyme-substrate complex, and \( P \) is product. The CORRECT statement(s) for the above reaction is/are

• A. Maximum possible rate of product formation is dependent on \( k_2 \) and initial concentration of enzyme.
• B. For a low substrate concentration, the rate of product formation is first order with respect to enzyme and also first order with respect to the substrate.
• C. The rate of product formation is independent of the concentration of enzyme-substrate complex.
• D. For a very high substrate concentration, initial rate of product formation is zero order with respect to the substrate.

Hint:

At low substrate concentrations, the reaction follows first-order kinetics with respect to both enzyme and substrate. At high substrate concentrations, the reaction becomes zero-order with respect to the substrate.

Answer 1

The Correct Option is A, B, D

Step 1: Understanding the Enzyme-Catalyzed Reaction.
The given reaction represents a typical enzyme-catalyzed reaction where the substrate \( S \) binds to the enzyme \( E \) to form the enzyme-substrate complex \( ES \), which then converts into the product \( P \) and regenerates the enzyme. The reaction rate is influenced by both the concentration of enzyme-substrate complex and the substrate.
Step 2: Analyzing the Options.
- (A) Maximum possible rate of product formation is dependent on \( k_2 \) and initial concentration of enzyme: This is correct because the rate of product formation is maximized when the enzyme-substrate complex is fully formed, and this depends on \( k_2 \) (the rate constant for product formation) and the concentration of enzyme.
- (B) For a low substrate concentration, the rate of product formation is first order with respect to enzyme and also first order with respect to the substrate: This is correct. At low substrate concentrations, the reaction is first order with respect to both the enzyme and substrate, meaning the rate is proportional to the concentration of both.
- (C) The rate of product formation is independent of the concentration of enzyme-substrate complex: This is incorrect. The rate of product formation is dependent on the concentration of the enzyme-substrate complex, as it directly affects the rate constant \( k_2 \).
- (D) For a very high substrate concentration, initial rate of product formation is zero order with respect to the substrate: This is correct. At very high substrate concentrations, the enzyme is saturated, and the rate of product formation becomes independent of the substrate concentration, thus behaving in a zero-order fashion with respect to the substrate.
Step 3: Conclusion.
The correct answers are (A), (B), and (D) because these accurately describe the behavior of the enzyme-catalyzed reaction in different substrate concentration regimes.