What is the effect of a non-competitive inhibitor on an enzyme?

A non-competitive inhibitor affects enzyme activity by binding to a site other than the active site, which causes a change in the shape of the enzyme itself. This alteration in shape can reduce the enzyme’s ability to catalyze the reaction effectively, regardless of how much substrate is present. The binding of a non-competitive inhibitor does not prevent the substrate from binding, but it changes the configuration of the enzyme in such a way that it can no longer function optimally.

This mechanism is distinct from that of competitive inhibitors, which do bind specifically to the active site of the enzyme, competing directly with the substrate. As a result, the presence of a non-competitive inhibitor can lead to a decrease in the maximum rate of reaction (Vmax) while the affinity of the enzyme for the substrate (as represented by Km) may remain the same because the same amount of substrate can still bind; however, the reaction cannot proceed as efficiently.