Catalyzes the hydrolytic deamination of adenosine and 2-deoxyadenosine (PubMed:8452534, PubMed:16670267). Plays an important role in purine metabolism and in adenosine homeostasis. Modulates signaling by extracellular adenosine, and so contributes indirectly to cellular signaling events. Acts as a positive regulator of T-cell coactivation, by binding DPP4 (PubMed:20959412). Its interaction with DPP4 regulates lymphocyte-epithelial cell adhesion (PubMed:11772392). Enhances dendritic cell immunogenicity by affecting dendritic cell costimulatory molecule expression and cytokines and chemokines secretion (By similarity). Enhances CD4+ T-cell differentiation and proliferation (PubMed:20959412). Acts as a positive modulator of adenosine receptors ADORA1 and ADORA2A, by enhancing their ligand affinity via conformational change (PubMed:23193172). Stimulates plasminogen activation (PubMed:15016824). Plays a role in male fertility (PubMed:21919946, PubMed:26166670). Plays a protective role in early postimplantation embryonic development (By similarity). adenosine + H(+) + H2O = inosine + NH4(+) Binds 1 zinc ion per subunit. Inhibited by Cu(2+) and Hg(2+), coformycin, deoxycoformycin (dCF), 2-deoxyadenosine, 6-methylaminopurine riboside, 2-3-iso-propylidene-adenosine and erythro-9-(2-hydroxy-3-nonyl)adenine. Interacts with DPP4 (via extracellular domain) (PubMed:10951221, PubMed:14691230, PubMed:7907293, PubMed:8101391, PubMed:15016824). Interacts with PLG (via Kringle 4 domain); the interaction stimulates PLG activation when in complex with DPP4 (PubMed:15016824). Colocalized with DPP4 at the cell surface. Found in all tissues, occurs in large amounts in T-lymphocytes (PubMed:20959412). Expressed at the time of weaning in gastrointestinal tissues. Up-regulated by hypoxia. There is a common allele, ADA*2, also known as the ADA 2 allozyme. It is associated with the reduced metabolism of adenosine to inosine. It specifically enhances deep sleep and slow-wave activity (SWA) during sleep. The disease is caused by variants affecting the gene represented in this entry. Belongs to the metallo-dependent hydrolases superfamily. Adenosine and AMP deaminases family. ADA mutation db Adenosine deaminase entry Leiden Open Variation Database (LOVD)