How do competitive and non-competitive inhibitors function in enzyme activity?

Competitive inhibitors bind to the active site of an enzyme, preventing substrate binding and reducing enzyme activity. Non-competitive inhibitors bind to a different site on the enzyme, changing its shape and reducing activity.

Competitive inhibitors compete with the substrate for binding to the active site of the enzyme. They do not react with the enzyme, but simply block the substrate from binding. This can be overcome by increasing the concentration of substrate, as the chance of substrate binding to the active site increases. Competitive inhibition can be used therapeutically, for example in the treatment of heart disease, where statins are used to inhibit the enzyme HMG-CoA reductase, reducing cholesterol production.

Non-competitive inhibitors bind to a different site on the enzyme, known as the allosteric site. This causes a conformational change in the enzyme, altering the shape of the active site and reducing enzyme activity. Non-competitive inhibition cannot be overcome by increasing substrate concentration, as the inhibitor is not competing for the active site. Non-competitive inhibition can also be used therapeutically, for example in the treatment of cancer, where methotrexate is used to inhibit the enzyme dihydrofolate reductase, reducing DNA synthesis in cancer cells.

Overall, competitive and non-competitive inhibitors both reduce enzyme activity, but through different mechanisms. Understanding the differences between the two types of inhibition is important in the development of therapeutic drugs and in understanding enzyme function.