Chymotrypsin is a recombinant serine endopeptidase expressed in E.coli, the gene sequence is the same as human chymotrypsin. Recombinant chymotrypsin hydrolyzes at the carboxyl side of aromatic amino acids residues: Tyr, Phe and Trp. Cleavage may also be observed, but at a lower rate, at Leu and Met. Chymotrypsin activity is optimal in pH 7.0–9.0.