How does a competitive enzyme inhibitor affect the kinetic parameters V_max and K_m of an enzyme-catalyzed reaction?
Answer and explanation
Correct answer: A. Leaves V_max unchanged and increases K_m
- Step 1: Recall the mechanism of competitive inhibition: the inhibitor reversibly binds the active site, competing with substrate.
- Step 2: At sufficiently high substrate concentrations, the inhibitor is outcompeted, so maximum reaction velocity () is unchanged. However, more substrate is required to reach half-maximal velocity, which increases .
Answer
Leaves V_max unchanged and increases K_m.
Why not the others: Decreasing while leaving unchanged characterizes non-competitive inhibition; decreasing both occurs in uncompetitive inhibition.
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