What is the difference between an allosteric inhibitor and a competitive inhibitor?

The distinction between an allosteric inhibitor and a competitive inhibitor is primarily rooted in how these inhibitors interact with the enzyme and influence its activity. Competitive inhibitors directly bind to the active site of an enzyme, competing with the substrate for that same active site. This competition means that increasing the concentration of substrate can effectively overcome the influence of the competitive inhibitor. Hence, when there is a higher concentration of substrate present, the likelihood of substrate molecules binding to the active site increases, which can restore enzyme activity despite the presence of the competitive inhibitor.

In contrast, allosteric inhibitors bind to a different site on the enzyme, known as the allosteric site. Their binding causes a conformational change in the enzyme's structure, which can either reduce its activity or completely inhibit it. This means that simply increasing substrate concentration will not alleviate the effect of an allosteric inhibitor, as it does not compete for the same binding site.

Therefore, saying that competitive inhibitors can be overcome by increasing substrate concentration accurately highlights a key functional difference between the two types of inhibitors.