Non-competitive inhibitors decrease enzyme activity by...

Non-competitive inhibitors decrease enzyme activity by...

• A. They compete with the substrate for the active site
• B. They bind to a site distant from the active site, causing conformational change
• C. They permanently destroy the enzyme
• D. They increase the affinity of the enzyme for the substrate

Answer: (B)

Non-competitive inhibition works by binding to a site other than the active site (an allosteric site) and causing a change in the enzyme’s shape. This conformational change lowers the enzyme’s catalytic efficiency, so the reaction rate drops even if substrate is abundant. The substrate can still bind, but the enzyme’s ability to convert it to product is impaired, reducing Vmax while Km remains largely unchanged. This differs from inhibitors that block the active site (competitive inhibition) and from scenarios where the enzyme is permanently destroyed, or where the inhibitor would increase substrate affinity—neither of which describes non-competitive inhibition.

Non-competitive inhibition works by binding to a site other than the active site (an allosteric site) and causing a change in the enzyme’s shape. This conformational change lowers the enzyme’s catalytic efficiency, so the reaction rate drops even if substrate is abundant. The substrate can still bind, but the enzyme’s ability to convert it to product is impaired, reducing Vmax while Km remains largely unchanged.

This differs from inhibitors that block the active site (competitive inhibition) and from scenarios where the enzyme is permanently destroyed, or where the inhibitor would increase substrate affinity—neither of which describes non-competitive inhibition.