Trypsin is a serine endopeptidase that specifically cleaves peptide bonds on the carboxy side of s-aminoethyl cysteine, arginine and lysine residues and typically there is little or no cleavage at arginyl-proline and lysyl-proline bonds. The distribution of these residues in proteins allows trypsin digestion to produce peptides that are readily identified by mass spectrometry.

Immobilised Trypsin is TPCK treated trypsin immobilised on 4% agarose that eliminates the contamination of protein digests by the trypsin. The immobilised trypsin is readily removed by separating the agarose from the digestion solution.