Chymotrypsin is a digestive
enzyme produced by the pancreas, and it is responsible for the breakdown of
proteins and polypeptides. Scientist John Northrop first crystallized chymotrypsin
in the twentieth century, but in the following years, other scientists
contributed to the characterization of this enzyme, and now, it is one of the
most well understood proteases. Specifically, it is an endopeptidase, and
breaks bonds within a polypeptide. Without chymotrypsin, proper food digestion cannot
occur. Chymotrypsin consists of two chains, and is made up of 245 amino acids
(Figure 1).


An important component of
chymotrypsin is the catalytic triad. This triad consists of residues Serine
195, Histidine 57, and Aspartate 102 (Figure 2). This triad is important for
chymotrypsin activity because the residues work to stabilize the enzyme and
promote catalysis. The aspartate and histidine are bound to each other by
hydrogen bonds, allowing histidine to work as a base for serine. Serine can
then become a nucleophile to catalyze the breakdown of proteins.