CD73 is a glycosyl phosphatidylinositol (GPI) anchored membrane protein that belongs to the 5-nucleotidase family. CD73 is an ecto 5Nucleotidase expressed by most cell types. CD73 hydrolyzes extracellular nucleotides into membrane permeable nucleosides. CD73 is one of several enzymes responsible for the production of extracellular adenosine, a signaling molecule that is involved in responses to inflammation and tissue injury. CD73 is a lymphocyte maturation marker that has functions independent of its catalytic activity. CD73 is also a regulator of leukocyte extravasation, a function that requires its 5Nucleotidase activity. Defects in NT5E are the cause of calcification of joints and arteries (CAJA). The recombinant CD73 lacking GPI anchor is secreted as a monomer. CD73 has been implicated as a prognostic indicator and therapeutic target in cancers. CD73 may act as an immune checkpoint inhibitor to natural killer cells in tumors, and this activity correlates with tumor invasiveness, metastasis, and poor outcome in cancer patients.
