Competitive inhibition

Definition

Competitive inhibition occurs when a molecule similar in structure to a substrate competes for binding at the active site of an enzyme. This prevents the actual substrate from binding, thereby inhibiting enzyme activity.

5 Must Know Facts For Your Next Test

1. Competitive inhibitors and substrates compete for the same active site on the enzyme.
2. The presence of a competitive inhibitor can be overcome by increasing substrate concentration.
3. Competitive inhibition does not affect the maximum rate (Vmax) of an enzyme-catalyzed reaction but increases the apparent Km (Michaelis constant).
4. Many drugs act as competitive inhibitors to block enzyme activity.
5. The effects of competitive inhibition are reversible when the inhibitor is removed.

Review Questions

• How does a competitive inhibitor affect the Km and Vmax of an enzyme-catalyzed reaction?
• Can competitive inhibition be reversed, and if so, how?
• Why might a drug designed as a competitive inhibitor be effective in treating diseases?

Related terms

Allosteric Inhibition: Allosteric inhibition occurs when an inhibitor binds to an enzyme at a site other than the active site, causing a change in its shape and reducing its activity.

Non-competitive Inhibition: Non-competitive inhibition involves an inhibitor binding to an enzyme at a different site than its active site, which decreases enzymatic activity regardless of substrate concentration.

Km (Michaelis constant): Km represents the concentration of substrate at which an enzyme operates at half its maximum velocity; it is used to measure enzyme affinity for its substrate.