Chymotrypsin (CTR)

Chymotrypsin is a digestive enzyme that can perform proteolysis. Chymotrypsin preferentially cleaves peptide amide bonds where the carboxyl side of the amide bond is a tyrosine, tryptophan, or phenylalanine. These amino acids contain an aromatic ring in their sidechain that fits into a 'hydrophobic pocket' of the enzyme.

The hydrophobic and shape complementarity between the peptide substrate P₁ sidechain and the enzyme S₁ binding cavity accounts for the substrate specificity of this enzyme.

Chymotrypsin also hydrolyzes other amide bonds in peptides at slower rates, particularly those containing leucine at the P₁ position. Chymotrypsin is synthesized in the pancreas by protein biosynthesis as a precursor called chymotrypsinogen that is enzymatically inactive.