Question

Given below are two statements:
Statement I: The catalytic efficiency of an enzyme cannot exceed the diffusion-controlled rate of the combination of enzyme and substrate to form Enzyme-Substrate (ES) complex.
Statement II: The catalytic efficiency of an enzyme is defined by the ratio, \(K_{\mathrm{cat}} / K_{\mathrm{m}}\).
In light of the above statements, choose the most appropriate answer from the options given below:

• A. Both Statement I and Statement II are correct
• B. Both Statement I and Statement II are incorrect
• C. Statement I is correct but Statement II is incorrect
• D. Statement I is incorrect but Statement II is correct

Hint:

Catalytic efficiency = \(K_{\mathrm{cat}} / K_{\mathrm{m}}\).
Upper limit is diffusion-controlled (\(\sim 10^8 - 10^9 \mathrm{M^{-1}s^{-1}}\)).

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
Enzyme catalytic efficiency is a measure of how effectively an enzyme converts substrate to product.
It is a key parameter in enzymology.

Step 2: Detailed Explanation:
Statement I:
The catalytic efficiency (\(K_{\mathrm{cat}} / K_{\mathrm{m}}\)) cannot exceed the diffusion-controlled rate of enzyme-substrate combination.
The diffusion-controlled limit is about \(10^8 - 10^9 \mathrm{M^{-1}s^{-1}}\).
Enzymes reaching this limit are considered "catalytically perfect."
This statement is true.
Statement II:
Catalytic efficiency is indeed defined by the ratio \(K_{\mathrm{cat}} / K_{\mathrm{m}}\).
\(K_{\mathrm{cat}}\) is the turnover number (product formed per enzyme per second).
\(K_{\mathrm{m}}\) is the Michaelis constant (measure of substrate affinity).
This statement is true.

Step 3: Final Answer:
Thus, both statements are correct, which corresponds to option (A).
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