Abstract
Matrix metalloproteinases and the related metalloproteases are implicated in cancer progression. They are endopeptidases that require several defined amino acid residues in both N-terminal and C-terminal sides of the scissile bond. Fluorogenic Forster resonance energy transfer (FRET) substrates that harbor a fluorophore and a quencher on opposite sides of the scissile bond are conveniently used to measure their activities. In this chapter, we describe the principle of FRET substrates and how to use them to measure activities and kinetic parameters of endopeptidases.