The catalytic triad is a specific arrangement of the three amino acid residues – serine, histidine and aspartate – within an enzyme, allowing the enzyme to have catalytic activity, according to Dr. Jeff Cronk from Gonzaga University. The catalytic activity is usually the cleavage of the peptide bond.
According to Dr. Cronk, the catalytic triad is present in serine protease enzymes, such as trypsin and chymotrypsin. The catalytic triad has arisen independently in serine proteases multiple times during the course of evolution. It is also present in the subtilisin enzyme found in bacteria and the carboxypeptidase enzyme from wheat germ.