Histone Acetyltransferases (HATs) are enzymes that acetylate histone substrates resulting in important regulatory effects on chromatin structure and assembly, and gene transcription. Modifications of these proteins by HATs play an important role in the control of gene expression, and their dysregulation has been linked to cancer, neurodegeneration, and other diseases. BioVision’s HAT Activity Assay Kit utilizes Acetyl CoA and H4 histone peptide as substrates. In this assay, HAT enzyme catalyzes the transfer of acetyl groups from Acetyl-CoA to the histone peptide, thereby generating two products - acetylated peptide and CoA-SH. The CoA-SH reacts with the developer and PicoProbeTM to generate a product that is detected fluorometrically at Ex/Em = 535/587 nm. The assay can detect HAT activity equivalent to as low as 1.5 µU of p300 in a variety of samples.