What are the characteristics of an irreversible inhibitor?

Irreversible inhibitors form strong, typically covalent bonds with the enzyme, permanently altering its structure or blocking its active site. This bond between the inhibitor and the enzyme is extremely strong, preventing the inhibitor from detaching and the enzyme from regaining its function. Even adding an excess amount of substrate will not reverse the inhibition caused by the irreversible inhibitor. The process often involves a chemical reaction between the inhibitor and a specific amino acid residue situated within the active site of the enzyme. Consequently, the enzyme remains permanently inactivated or significantly hindered in its ability to catalyze reactions, unless new enzyme molecules are synthesized to replace those that were irreversibly inhibited. As an example, when aspirin interacts with cyclooxygenase, it acetylates a serine amino acid within the enzyme's active site. This acetylation causes a stable alteration in the enzyme's structure, resulting in irreversible inhibition and the modified enzyme loses its ability to function effectively. To restore the enzyme's activity, new molecules of cyclooxygenase must be synthesized to replace the irreversibly inhibited enzymes that have undergone modification due to the interaction with aspirin.