Non-competitive Inhibitors

Non-competitive inhibitors are chemically unlike the enzyme's true substrate, yet they can still bind to the enzyme, typically at a site distinct from the active site. This binding either physically blocks the substrate from reaching the active site, or changes the overall shape of the enzyme so that the active site can no longer properly accept the substrate. One example is the effect of the amino acid alanine on the enzyme pyruvate kinase at the final step of glycolysis. Some inhibitors go a step further and bind the enzyme irreversibly, permanently and completely destroying its catalytic ability - these are effectively poisons. Cyanide ions, for instance, permanently block cytochrome oxidase, a key enzyme in the terminal step of aerobic cellular respiration, while the ne …