Trypsin （EC3.4.21.4） is part of the serine protease family. Trypsin cleaves lysine and arginine at the C-terminal side of the peptide. The hydrolysis rate is slower if an acidic residue is on either sides of the cleavage site and no cleavage occurs if a proline residue is on the carboxyl side of the cleavage site. Trypsin optimum pH is pH-7 to 9. Trypsin will also hydrolyze ester and amide linkages of synthetic derivatives of amino acids such as: benzoyl L-arginine ethyl ester （BAEE）， p-toluenesulfonyl- L-arginine methyl ester （TAME）， tosyl-L-arginine methyl ester， N-a-benzoyl-L-arginine p-nitroanilide （BAPNA）， L-lysyl-p-nitroanilide， and benzoyl-L-tyrosine ethyl ester （BTEE）. Serine protease inhibitors that inhibit recombinant trypsin include TLCK （N-p-tosyl-L-lysine chloromethyl ketone）， PMSF （phenylmethanesulfonyl fluoride）， benzamidine， soybean trypsin inhibitor， and ovomucoid.
