CD39 is an ectoenzyme (ecto-nucleotide triphosphate diphosphohydrolase 1, encoded by ENTPD1 gene) belonging to the family of ectonucleotidases which comprises ecto-5'-nucleotidase (NT5E)/CD73, CD38/NADase, NAD glycohydrolases, nucleoside diphosphate kinase, ecto-nucleotide pyrophosphate phosphodiesterases (E-NPPs), ecto nucleoside triphosphate diphosphohydrolases (ENTPDases), and adenylate kinases [PMID: 34360833].