Fig. (1) Schematic for identifying protease specificity A: Substrate structure, where the N-terminal amine is labeled with biotin and X indicates 20 amino acids. B: The procedure for determining protease specificity. Cleaved and non-cleaved substrates are purified with streptavidin-beads, after which the substrates are tested by MALDI-TOF mass spectrometry. Protease specificity is determined using the mass spectrometry results.