Type II transmembrane serine proteases are an emerging class of proteo-lytic enzymes involved in tissue homeostasis and a number of human disor-ders such as cancer. To better define the biochemical functions of a subset of these proteases, we compared the enzymatic properties of matriptase, matriptase-2, hepsin and DESC1 using a series of internally quenched fluorogenic peptide substrates containingo-aminobenzoyl and 3-nitro-tyro-sine.