The JARID1B Homogeneous Assay Kit is designed to measure JARID1B activity for screening and profiling applications. JARID1B, also known as PLU-1 and KDM5B, is a JumonjiC (JmjC) and ARID domain-containing histone lysine demethylase that exhibits demethylation activity toward H3-K₄Me² and H3-K₄Me³. The JARID1B Homogeneous Assay Kit comes in a convenient AlphaLISA^® format (Scheme 1), with biotinylated histone H3 peptide substrate, primary antibody, demethylase assay buffer, and purified JARID1B for 96 or 384 enzyme reactions. The key to the JARID1B Homogeneous Assay Kit is a highly specific antibody that recognizes demethylated substrate. With this kit, only three simple steps on a microtiter plate are required for methyltransferase detection. First, a sample containing JARID1B enzyme is incubated with the biotinylated substrate. Next, acceptor beads and primary antibody are added, then donor beads, followed by reading the Alpha-counts. Our histone demethylase assays utilize highly specific antibodies that recognize demethylated products. First, a sample containing the enzyme is incubated with a biotinylated substrate. Next, acceptor beads and primary antibody are added, then donor beads, followed by reading the Alpha-counts.