Scientist John Northrop is
known for crystallizing many enzymes and proteins. One important enzyme he
crystallized was chymotrypsin. Chymotrypsin is a digestive enzyme produced by
the pancreas, and it is responsible for the breakdown of proteins and
polypeptides. Specifically, chymotrypsin breaks bonds within a polypeptide,
classifying it as an endopeptidase. Without chymotrypsin, proper food digestion
cannot occur.

Chymotrypsin consists of two
chains, and is made up of 245 amino acids (Figure 1). In the following years
after Northrop’s crystallization, other scientists contributed to the
characterization of this enzyme, and now, it is one of the most well understood

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The catalytic triad is an
important component of chymotrypsin. This triad consists of residues Serine
195, Histidine 57, and Aspartate 102 (Figure 2) and works 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.