Chymotrypsin
There are several steps throughout the digestive tract to break down
proteins into pieces so that they can be absorbed in the body. One of
them is chymotrypsin.
Chymotrypsin is a digestive enzyme belonging to a super family of
enzymes called serine proteases. This enzyme is synthesized in pancreas
and it is used for digesting proteins. Chymotrypsin is found in the
duodenum that selectively cleaves (cuts) off pieces of amino acids from
the protein chain. Specifically, chymotrypsin cleaves phenylalanine,
tyrosine, and tryptophan.
Structure of Chymotrypsin
This enzyme is a spherical protein and consists of three polypeptide
chains and a pocket which is lined with relatively hydrophobic residues.
These hydrophobic molecules attract substrate with hydrophobic region
in its molecular structure. The active site forms a catalytic triad which
includes serine (Ser-195), histidine (His-57), and aspartic acid (Asp-
102). Ser-195 is hydrogen bonded to the His-57 and it in turn is
hydrogen bonded to the Asp-102 residue.
Mechanism of Chymotrypsin
Chymotrypsin catalyzes the cleavage of peptide bonds in the target
protein by hydrolysis reaction. It is a proteolytic enzyme (protease)
which breaks long chain peptide bonds of proteins in smaller parts.
Hydrolysis of peptide bond by chymotrypsin is a two-step displacement
reaction which involves:
Formation of amine group
Formation of acid group
Reaction is as follows;
