Description_x000D_ Application_x000D_ This is the protein activator required for the Ca2+ dependent activation of phosphodiesterase, 3′:5′-cyclic nucleotide, P0520._x000D_ Biochem/physiol Actions_x000D_ Ca2+ binding protein that is required for activation of cyclic nucleotide-dependent phosphodiesterase. It is also a cofactor/activator of nitric oxide synthase, calcineurin, and many kinases including ATPase, myosin light chain kinase, and CAM kinase I, II, and III. It mediates ryanodine receptor activation by cyclic ADP ribose and is involved in intracellular Ca2+ homeostasis._x000D_ Unit Definition_x000D_ One unit will stimulate 0.008 activated unit of phosphodiesterase, 3′:5′-cyclic nucleotide, P0520, in a 3 mL reaction volume at pH 7.5 and 30 °C, to 50% of the maximum activity of the enzyme when saturated with activator, in the presence of 0.01 mM Ca2+._x000D_ Physical form_x000D_ Lyophilized powder containing buffer salts as imidazole and magnesium sulfate_x000D_ Preparation Note_x000D_ Purified by a modification of the procedure of Teo, T.S., et al., J. Biol. Chem., 248, 588 (1973).