Trypsin-ultra, Mass Spectrometry Grade from New England Biolabs

Modified Trypsin (TPCK-treated) is a serine endopeptidase. It selectively cleaves peptide bonds C-terminal to lysine and arginine residues (1). Modified Trypsin is treated with L-(tosylamido-2-phenyl) ethyl chloromethyl ketone (TPCK) to inactivate any remaining chymotryptic activity. It is modified by acetylation of the e-amino groups of lysine residues to prevent autolysis. Modified Trypsin cleaves at Lys-Pro and Arg-Pro bonds at a much slower rate than other amino acid residues (2).