Bovine Chymotrypsin is a serine endopeptidase produced by the acinar cells of the pancreas. Chymotrypsin becomes activated after proteolysis of chymotrypsinogen by trypsin. While trypsin hydrolyzes at lysine and arginine, chymotrypsin selectively cleaves peptide bonds formed by aromatic residues (tyrosine, phenylalanine, and tryptophan) (Hedstromet al.1992). Two predominant forms of chymotrypsin, A and B, are found in equal amounts in cattle pancreas. They are very similar proteins (80 identical), but have significantly different proteolytic characteristics (Hartley 1964, Melounet al.1966, Smillieet al.1968, and Grfet al.2004). The information below pertains primarily to the A form of chymotrypsinogen and chymotrypsin.