Which is an example of a non-competitive inhibitor?

Which is an example of a non-competitive inhibitor?

• A. Methotrexate
• B. Substrate analog
• C. Salts
• D. Alanine and ATP

Answer: (C)

Non-competitive inhibition involves inhibitors binding to a site other than the active site, causing a change in enzyme shape that reduces activity even when the substrate is present. This lowers the maximum rate (Vmax) while Km stays roughly the same. Salts fit this idea because they don’t compete with the substrate for the active site; instead, they alter the enzyme’s environment or conformation, decreasing catalytic efficiency regardless of substrate concentration. The other options are more typical of competitive inhibition (methotrexate and substrate analogs) or are actual substrates/cofactors (alanine and ATP), not inhibitors.

Non-competitive inhibition involves inhibitors binding to a site other than the active site, causing a change in enzyme shape that reduces activity even when the substrate is present. This lowers the maximum rate (Vmax) while Km stays roughly the same. Salts fit this idea because they don’t compete with the substrate for the active site; instead, they alter the enzyme’s environment or conformation, decreasing catalytic efficiency regardless of substrate concentration. The other options are more typical of competitive inhibition (methotrexate and substrate analogs) or are actual substrates/cofactors (alanine and ATP), not inhibitors.