Question

A competitive inhibitor of an enzyme

• A. Decreases the Km
• B. Decreases the $V_{max}$
• C. Decreases both the Km & $V_{max}$
• D. Increases the Km

Answer 1

Answer: (D)

In competitive inhibition of enzyme catalysis, binding of an inhibitor prevents binding of the target molecule of the enzyme, also known as the substrate. This is accomplished by blocking the binding site of the substrate: the active site. Competitive inhibition can be overcome by adding more substrate to the reaction, which increases the chances of the enzyme and substrate binding. As a result, competitive inhibition alters only the Km, leaving the $V_{max}$ the same.