Chymotrypsin, trypsin, and elastase aredigestive enzymes called serine proteases. The serine proteasesdiffer in substrate specificity: Chymotrypsin cleaves peptide bondsafter aromatic or bulky hydrophobic side chains; trypsin requiresbasic amino acid residues; and elastase cleaves bonds followingsmall uncharged side chains. A chart of amino acids can be foundhere. The specificity pockets (substrate-binding sites) of each ofthe serine proteases are drawn below.