P¹,P⁵-Di(adenosine-5') pentaphosphate pentasodium salt

A diadenosine polyphosphate stored in secretory granules of chromaffin and neuronal cells and thrombocytes. After release into the extracellular space, the compound affects a variety of biological activities in a wide range of target tissues. In the nervous system it acts through various purinergic receptors. It also activates 5'-nucleotidase and inhibits adenosine kinase activity in vitro. Ap5A is metabolized by soluble enzymes in the blood plasma and by membrane-bound ectoenzymes of a number of cell types including endothelial and smooth muscle cells.