Phosphodiesterases (PDEs) play an important role in the dynamic regulation of cAMP and cAMP signaling. Mouse PDE3A, also known as cAMP-inhibited phosphodiesterase, has been implicated in cardiovascular function and fertility. The Mouse PDE3A1 Assay Kit is designed for identification of inhibitors of Mouse PDE3A1 using fluorescence polarization. The assay is based on the binding of a fluorescent nucleotide monophosphate generated by Mouse PDE3A1 to the binding agent.Phosphodiesterases catalyze the hydrolysis of the phosphodiester bond in dye-labeled cyclic monophosphates. Beads selectively bind the phosphate group in the nucleotide product. This increases the size of the nucleotide relative to unreacted cyclic monophosphate. In the polarization assay, dye molecules with absorption transition vectors parallel to the linearly-polarized excitation light are selectively excited. Dyes attached to the rapidly-rotating cyclic monophosphates will obtain random orientations and emit light with low polarization. Dyes attached to the slowly-rotating nucleotidebead complexes will not have time to reorient and therefore will emit highly polarized light.