Native protein purified from Bovine Pancreas according to the procedure of Yapel et al., J. Amer. Chem. Soc., 88, 2573 (1966)
>=45 units per mg protein. One Unit hydrolyzes one micromole of benzoyl-L-tyrosine ethyl ester per minute at 25°C, pH 7.8 in the presence of calcium. An activity of 45 units per mg using the above definition, is the equivalent of 10,000 optical density or 1330 N.F. units per mg using ATEE as a substrate. 1 BTEE unit = 29.5 USP/NF units.
Chymotrypsin is a serine endopeptidase activated after proteolysis by trypsin. It preferentially catalyzes the hydrolysis of peptide bonds involving L-isomers of tyrosine, phenylalanine and tryptophan. It also readily acts upon amides and esters of susceptible amino acids.