Summary: The HDAC fluorometric cellular activity assay allows the determination of deacetylase activity within an undisturbed cellular environment and provides accurate activity information that is reflective of endogenous regulation. It also allows the study of the effects of upstream regulators on deacetylase activity and the detection of inhibitors or activators that act indirectly to affect deacetylase activity. The FLUOR DE LYS HDAC substrate is cell permeable. It is deacetylated by cellular HDACs and thus suitable for high-throughput cell-based deacetylase assays. This kit provides the reagents and protocols needed for determining rates of intracellular deacetylase activity with cultured cells. Deacetylation can be quantitated by addition of developer to the media and lysed cells.