5′-nucleotidase (5′-NT), also known as ecto-5′-nucleotidase or CD73 (cluster of differentiation 73), is an enzyme that in human is encoded by the NT5E gene. CD73 commonly serves to convert AMP to adenosine. NT5E contains binding sites for transcription factors AP-2, SMAD proteins, SP-1 and elements responsive to c-AMP, which can be found in c-AMP promoter parts. This enzyme consists of a dimer of 2 identical 70-kD subunits bound by a glycosyl phosphatidyl inositol linkage to the external face of the plasma membrane, and CD73 is used as a marker of lymphocyte differentiation.