Background
Adenosine 5'-diphosphate (ADP) is an adenine nucleotide containing two phosphate groups esterified to the sugar moiety at the 5’ position. It is produced by dephosphorylation of adenosine 5’-triphosphate by ATPases and can be converted back to ATP by ATP synthases. ADP can also be metabolized to adenosine 5’-monophosphate and 2’-deoxyadenosine 5’-diphosphate (dADP). ADP can modulate several receptors, activating certain purinergic receptors (EC50 = 24 nM for P2Y1) and inhibiting others (IC50 = 67 nM for P2X2/3), inhibiting rat ecto-5’nucleotidase (Ki = 0.91 nM), and regulating the phosphorylation status of AMP-activated protein kinase (AMPK).1,2,3,4