Pepsin is an endopeptidase that breaks down proteins into smaller peptides.It is one of three principal proteases in the human digestive system, the other two being chymotrypsin and trypsin.
Pepsin is a member of the small family of closely related aspartic proteinase enzymes. Pepsin hydrolyzes proteins and petides, including those with bonds adjacent to aromatic or dicarboxylic L-amino acid residues; preferential cleavage: Phe- and Leu-.