This is the protein activator required for the Ca²⁺ dependent activation of phosphodiesterase, 3′:5′-cyclic nucleotide, P0520.

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.

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⁺.

Lyophilized powder containing buffer salts as imidazole and magnesium sulfate

Purified by a modification of the procedure of Teo, T.S., et al., J. Biol. Chem., 248, 588 (1973).