Useful for assaying lysates, immunoprecipitates or inhibitor screening using the nuclear extract provided.- Includes HeLa nuclear extract, a rich source of HDACs 1 & 2 for use as a positive control or as a source of HDAC activity for screening. Compatible with class I & IIb HDAC and sirtuins (with addition of NAD+). The COLOR DE LYS system is a sensitive and convenient alternative to protocols utilizing radiolabeled, acetylated histones or peptide/HPLC methods for the assay of histone deacetylases. The assay procedure has two steps. First, the COLOR DE LYS substrate which comprises an acetylated lysine side chain, is incubated with a sample containing HDAC activity . Deacetylation of the substrate sensitizes the substrate so that, in the second step, mixing with the COLOR DE LYS developer causes an increase in yellow color intensity, and absorption at 405 nm. Alternative name: Histone deacetylase colorimetric assay kit. Applications: Colorimetric detection, HTS Activity assay.