What is the difference between competitive and non-competitive enzyme inhibitors, and how do they affect enzyme function?

Sourav PanNovember 9, 2024

Answered

Competitive and non-competitive enzyme inhibitors are two distinct types of molecules that interfere with enzyme activity, but they do so through different mechanisms and with varying effects on enzyme function.

Competitive Inhibition

Mechanism: Competitive inhibitors resemble the substrate’s structure and compete for binding to the enzyme’s active site. When a competitive inhibitor binds to the active site, it prevents the substrate from attaching, effectively blocking the reaction. This type of inhibition is reversible, meaning that increasing the concentration of substrate can overcome the inhibition by outcompeting the inhibitor for the active site.Effects on Enzyme Function:

• Vmax (Maximum Reaction Rate): Remains unchanged because, at high substrate concentrations, the effect of the inhibitor can be overcome.
• Km (Michaelis Constant): Increases, indicating a higher concentration of substrate is needed to reach half of Vmax due to the competition for the active site.

Non-Competitive Inhibition

Mechanism: Non-competitive inhibitors bind to an allosteric site on the enzyme, which is distinct from the active site. This binding does not prevent substrate binding; however, it alters the enzyme’s shape or conformation, reducing its catalytic efficiency. Thus, even if the substrate is bound, the enzyme cannot effectively convert it into product.Effects on Enzyme Function:

• Vmax: Decreases because non-competitive inhibitors effectively reduce the amount of functional enzyme available for catalysis.
• Km: Remains unchanged, as the inhibitor does not affect substrate binding directly; instead, it reduces the overall effectiveness of the enzyme-substrate complex.

Summary of Differences