Inc. All Rights Reserved. If an inhibitor binds reversibly to the same site as the substrate, the inhibition will be competitive.
Competitive inhibitors are common in nature.
One way to measure the effect of an inhibitor is to measure enzyme velocity at a variety of substrate concentrations in the presence and absence of an inhibitor. As the graph below shows, the inhibitor substantially reduces enzyme velocity at low concentrations of substrate, but doesn't alter velocity very much at very high concentrations of substrate. You'll get a more reliable determination of Ki if you determine the observed K m at a variety of concentrations of inhibitor. Fit each curve to determine the observed Km. Enter the results onto a new table, where X is the concentration of inhibitor, and Y is the observed Km.