chymotrypsin is a proteolytic enzyme that digests proteins in the small intestine.

It is synthesized in the pancrease and secreted into the pancreatic duct as the inactive proenzyme called chymotrypsinogen. In the small intestine the chymotrypsinogen is proteolytically cleaved to yield the active fragment called chymotrypsin.

Chymotrypsin is classified as a serine protease because there is a serine at the active site of the enzyme that directly participates in the breaking of the peptide bond. The active site of chymotrypsin contains the side chains of aspartate 102 (aspartate 102 is the 102 nd amino acid from the N-terminal end of chymotrypsin), the side chain of histidine-57 and the side chain of serine-195.