These Serine Protease Assay Kits enable researchers to detect intracellular chymotrypsin-like serine protease activity in vitro without lysing the cell.

FLISP® (Fluorescent Labeled Inhibitors of Serine Proteases) reagents are non-cytotoxic green or red fluorescent inhibitors that covalently bind with active serine protease enzymes. FLISP is a powerful method to assess the intracellular levels of chymotrypsin- like serine protease activity in vitro. Just add FLISP directly to the cell culture media, incubate, and wash. Because FLISP inhibitors are cell-permeant, they will efficiently diffuse in and out of all living cells. If there is an active chymotrypsin-like enzyme inside the cell, it will covalently bind with the FLISP inhibitor and retain the green or red fluorescent signal within the cell. Cells containing lower concentrations of chymotrypsin-like enzyme activity will retain a lower level of fluorescence compared to cells containing higher concentrations of this effector enzyme. There is no interference from pro-enzymes nor inactive forms of the enzymes. If the treatment is activating chymotrypsin-like serine proteases, positive cells will fluoresce brighter than the normal baseline negative cells, thus enabling researchers to clearly differentiate the populations.