How do inhibitors affect enzyme activity?

Inhibitors affect enzyme activity by reducing the rate of enzyme-catalysed reactions, either temporarily or permanently.

Enzymes are biological catalysts that speed up chemical reactions in cells. They work by providing an alternative reaction pathway with a lower activation energy. However, the presence of inhibitors can disrupt this process, leading to a decrease in the rate of enzyme-catalysed reactions.

Inhibitors can be classified into two main types: competitive and non-competitive. Competitive inhibitors are molecules that have a similar structure to the substrate, the molecule that the enzyme acts upon. They compete with the substrate for the active site of the enzyme, the region where the substrate binds and the reaction takes place. If a competitive inhibitor binds to the active site, it blocks the substrate from binding, thus preventing the enzyme from catalysing the reaction. However, this inhibition is not permanent; increasing the concentration of the substrate can outcompete the inhibitor and restore the enzyme's activity.

Non-competitive inhibitors, on the other hand, do not compete with the substrate for the active site. Instead, they bind to another part of the enzyme, causing a change in the enzyme's shape. This change can prevent the substrate from binding to the active site or it can prevent the enzyme from catalysing the reaction even if the substrate can still bind. Unlike competitive inhibition, non-competitive inhibition cannot be overcome by increasing the substrate concentration.

In addition to these, there are also irreversible inhibitors that form strong covalent bonds with enzymes, permanently inactivating them. These are often toxic and are used as drugs or pesticides.

In summary, inhibitors affect enzyme activity by interfering with the binding of the substrate or the catalysis of the reaction, thereby reducing the rate of enzyme-catalysed reactions. Understanding how inhibitors work is crucial in many fields, including medicine and agriculture, as they can be used to control enzyme activity.