Enzyme Inhibition

Specific chemicals can regulate the action of enzymes by inhibiting, or blocking, their function. Enzyme inhibitors come in two different forms: competitive and non-competitive.

A competitive inhibitor is similar enough to the enzyme's specific substrate that it can bind to the active site and block the substrate from binding. This action essentially decreases the number of enzymes available to bind to the substrate.

In contrast, a non-competitive inhibitor will bind away from, but still influence, the active site by changing the enzyme's shape, for example, and greatly reducing the affinity for the substrate binding to the active site, preventing the enzyme from functioning properly.

In addition, both types of inhibitors differentially affect the rate of a chemical reaction.

Compared to a control, a normal enzymatic reaction rate, a reaction including a competitive inhibitor would take longer to reach Vmax, the maximum reaction rate, and would require more substrate to do so, as there must be enough substrate to consistently outcompete the inhibitor for access to the active sites.

On the other hand, a non-competitive inhibitor would not allow the rate to reach Vmax, because the number of enzymes available for binding is reduced.