Proteolytic enzymes

They catalyze the hydrolysis of peptide bonds in other proteins. In order to prevent them doing generalized damage to all cellular proteins, they are often synthesized in an inactive form known as a 'proenzyme' or 'zymogen' and activated as required. Such enzymes include the  serine proteases, so called because of the presence  in the active site of an essential serine residue, i.e. a serine residue whose presence is essential for the enzymic activity. The serine proteases, chymotrypsin, trypsin and elastase, which are produced in an inactive form by the mammalian pancreas, form a closely related group of enzymes.