Ectonucleoside triphosphate diphosphohydrolase-1 (gene: ENTPD1; protein:NTPDase1) also known as CD39 (Cluster of Differentiation 39), is a typical cell surface-located enzymes with an extracellularly facing catalytic site. NTPDase1 is an ectonucleotidase that catalyse the hydrolysis of γ- and β-phosphate residues of triphospho- and diphosphonucleosides to the monophosphonucleoside derivative. For example, NTPDase1 hydrolyzes P2 receptor ligands, namely ATP, ADP, UTP and UDP with similar efficacy. NTPDase1 can therefore affect P2 receptor activation and functions.