The p300 Homogeneous Assay Kit contains an AlphaLISA^® assay designed for screening inhibitors of p300 in a convenient 384-well format. This efficient method requires no time-consuming washing steps. Only a few steps are needed. The assay is based on the enzymatic transfer of an acetyl group from acetyl CoA to a specific lysine residue within a biotinylated peptide substrate. After incubation with p300, the sample is incubated with a combination of an antibody that specifically binds the acetylated peptide and acceptor beads that bind the antibody. This is followed by incubation with streptavidin-labeled donor beads and reading of the Alpha-counts.