Koshland has proposed the induced fit theory of enzyme action. This concept implies that:
A) the template or lock-and-key theory adequately explains the mechanism of enzyme catalysis.
B) the active site is flexible; the catalytic group(s) of the enzyme is/are brought into proper alignment by the substrate.
C) the conformation of the substrate changes before binding to the enzyme.
D) the formation of the enzyme-substrate complex is always the fastest step in an enzyme catalyzed reaction.

Question

Quizplus · Accepted Answer

The induced fit theory proposed by Koshland suggests that the active site of an enzyme is flexible and undergoes a conformational change upon binding with the substrate. This allows the catalytic groups of the enzyme to be brought into proper alignment with the substrate, leading to an increase in the efficiency of the reaction. Therefore, option B is the correct choice. Option A is incorrect as it states that the lock-and-key theory is sufficient, whereas the induced fit theory proposes a more dynamic mechanism of enzyme action. Option C is incorrect as it suggests that the substrate undergoes a conformational change prior to binding; however, it is the enzyme that undergoes the change. Option D is incorrect as the rate-limiting step of an enzyme-catalyzed reaction can vary and may not always be the formation of the enzyme-substrate complex.

Koshland Has Proposed the Induced Fit Theory of Enzyme Action