Fluorogenic substrates are effective tools for assessing the activity of proteases in media, cell or tissue lysates. Proteases, such as MMPs, are scissor-like proteins whose job is to cut certain amino acid sequences that exist within other proteins, such as collagen. Fluorogenic substrates (also known as FRET substrates) are designed with an amino acid sequence that is cleavable by the protease of interest. They are also designed in such a way that when a protease cuts the substrate, a fluorescent dye gets released and starts emitting a fluorescent signal. The amount of signal detected is therefore directly related to how much protease activity there is in a given sample.
Here is what we have so far written regarding Fluorogenic Substrate Assays: