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

Fluorescent inhibitor reagents are non-cytotoxic green or red fluorescent inhibitors that covalently bind with active serine protease enzymes. This approach is a powerful method to assess the intracellular levels of chymotrypsin- like serine protease activity in vitro. Just add the fluorescent inhibitor reagent directly to the cell culture media, incubate, and wash. Because these 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 fluorescent inhibitor  reagent 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.