Which type of inhibitor alters an enzyme's 3D shape instead of competing for the active site?

Noncompetitive inhibitors are distinct because they bind to an enzyme at a site other than the active site, which induces a change in the enzyme's three-dimensional structure. This alteration affects the enzyme's ability to catalyze a reaction, reducing its efficacy regardless of whether the substrate is present. Unlike competitive inhibitors, which compete directly for the active site and can be outcompeted by increasing substrate concentration, noncompetitive inhibitors maintain their effect even in the presence of substrate.

In cases of noncompetitive inhibition, the enzyme can still bind the substrate; however, the reaction rate decreases because the enzyme's configuration prevents an effective conversion of substrate to product. On the other hand, irreversible inhibitors permanently modify the enzyme and effectively eliminate its activity, while pseudoreversible inhibitors can bind non-covalently but typically do not induce as significant a change in the enzyme compared to noncompetitive inhibitors. Thus, the impact of noncompetitive inhibitors on the three-dimensional structure of enzymes is key to their function and characteristic activity within biological systems.