Scientist John Northrop crystallized
many enzymes and proteins in the early twentieth century. One important enzyme
he crystallized was chymotrypsin, a digestive enzyme. In the following years
after his crystallization, other scientists contributed to the characterization
of this enzyme, and now, it is one of the most well understood proteases.
Chymotrypsin, as previously
mentioned, is a digestive enzyme produced by the pancreas. Without it, proper
food digestion cannot occur, as it is responsible for the break down of
proteins. Chymotripsin can be classified as an endopeptidase because it breaks
proteins within the polypeptide. Structurally, chymotrypsin consists of two
chains, and is made up of 245 amino acids (Figure 1).
The catalytic triad is an important component of chymotrypsin.
This triad consists of residues Serine 195, Histidine 57, and Aspartate 102
(Figure 2). Together, they 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.