5'-Nucleotidase (also [ecto]-5'-nucleotidase/5'-NT, designated CD73) is a variably glycosylated, 69-73 kDa member of the 5'-Nucleotidase family of enzymes. It is expressed on multiple cell types, including vascular endothelium, transitional and nonkeratinized epithelium, cardiomyocytes, small intestine epithelium, FoxP3⁺ Treg lymphocytes, FDCs and B cells. 5'-Nucleotidase hydrolyzes AMP to adenosine and phosphate. This creates diffusible nucleosides necessary for cell homeostasis, and a ligand for cell membrane adenosine receptors. Mature human 5'-Nucleotidase is a 523 amino acid (aa) GPI-linked protein (aa 27-549). It contains a large Zn‑dependent nucleotidase catalytic region (aa 28-532) and a C-terminal substrate binding site (aa 500-506). On the cell surface it exists as a disulfide-linked homodimer. Two splice variants are reported. One shows a deletion of aa 405-454, and a second possesses a 12 aa substitution for aa 253-574. Over aa 1-511, human 5'‑Nucleotidase shares 88% aa identity with both mouse and rat 5'-Nucleotidase.