An irreversible chance is a change that is impossible to reverse; this is often seen in chemistry or physics as a change that can only go in one direction, notes TheFreeDictionary.com. For example, Tosyl-L-phenylalanine chloromethylketone, which is an inhibitor of the enzyme chymotrypsin, is an example for irreversible change.
It is an irreversible inhibitor also classified as a non-competitive inhibitor. This inhibitor undergoes irreversible change, by forming a covalent bond with an amino acid in the enzyme active site.
The peptide hydrolysis is catalyzed by the enzyme chymotrypsin, at the carbonyl side of the amino acids, tyrosine, phenylalanine and tryptophan. The inhibitor, attaches covalently to the Histidine-57 of the active site of the enzyme. This reaction of the inhibitor remains irreversible, as the shape of the enzyme and its active site are modified permanently. The enzyme is no more beneficial for the substrate to react with it.