Explain Competitive Inhibition of Enzyme With an Example
Competitive Inhibition of Enzyme
Competitive inhibition occurs when a molecule similar in structure to the substrate competes with the substrate for binding to the enzyme’s active site. This inhibitor prevents the substrate from binding, but does not alter the enzyme itself. The effect can be overcome by increasing substrate concentration.
Key Points:
Inhibitor resembles substrate and binds to the active site.
Reversible process: Adding more substrate can outcompete the inhibitor.
No change in Vmax (maximum velocity); Km (substrate concentration at half Vmax) increases.
Example with Real Data
Enzyme: Succinate dehydrogenase
Substrate: Succinate
Competitive inhibitor: Malonate
Malonate closely resembles succinate and competes for the active site of succinate dehydrogenase.
When malonate is present, the enzyme’s ability to convert succinate into fumarate is reduced unless excess succinate is added.
Real Data:
In a laboratory assay, adding 0.1mM malonate decreases succinate dehydrogenase activity by 40% if the succinate concentration is 0.5mM.
Increasing succinate concentration to 5mM restores most of the enzyme's activity.
Summary Table
| Enzyme | Substrate | Competitive Inhibitor | Real Data Effect |
|---|---|---|---|
| Succinate dehydrogenase | Succinate | Malonate | 0.1mM malonate inhibits activity by 40% |
Competitive inhibition is reversible and can be overcome by increasing substrate concentration. A classic example is malonate inhibiting succinate dehydrogenase in the Krebs cycle.