Proteases are a family of enzymes that cleave proteins and peptides at site-specific peptide linkages within their structures. They are further classified as either endopeptidases, which cleave proteins or peptides at internal peptide linkages, or exopeptidases, which can cleave the terminal amino-acid residues from peptides or proteins. Marker Gene sells a variety of chromogenic, fluorogenic or secondary enzyme specific protease substrates or kits for use in assay development and research. Many of these substrates and kits are specific for important intracellular enzymes such as the Caspases, Calpains, Cathepsins used in apoptosis research. Please see the list below for more information about individual products.