{"entity":{"id":"ada","kind":"target","name":"Adenosine deaminase (ADA)","aka":[],"tldr":"Adenosine deaminase is an enzyme that breaks down adenosine and deoxyadenosine; blocking it with pentostatin poisons lymphocytes, which is why the drug works in hairy cell leukaemia and some T-cell cancers.","summary":"Adenosine deaminase (ADA) converts adenosine to inosine and deoxyadenosine to deoxyinosine in the purine salvage pathway. Lymphocytes depend on it: children born without ADA have severe combined immunodeficiency because deoxyadenosine metabolites accumulate and kill developing lymphocytes. Pentostatin (deoxycoformycin) is a tight-binding ADA inhibitor that reproduces this toxicity on purpose in lymphoid cancers, producing durable remissions in hairy cell leukaemia; it is also used in T-cell leukaemias and lymphomas and in graft-versus-host disease.","asOf":"2026-09-04","wikipedia":"https://en.wikipedia.org/wiki/Adenosine_deaminase","links":[{"label":"UniProt P00813: ADA","url":"https://www.uniprot.org/uniprotkb/P00813/entry"},{"label":"HGNC:186 ADA","url":"https://www.genenames.org/data/gene-symbol-report/#!/hgnc_id/HGNC:186"}],"tags":[],"related":[],"cancers":["hairy-cell-leukemia","cll"],"sections":[],"technologies":[],"targets":[],"drugs":["pentostatin"],"companies":[],"institutions":[],"pathways":[],"terms":["apoptosis"],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"symbol":"ADA","role":[],"sources":[],"specificity":"lineage-antigen","distribution":"one-type","specificityNote":"Lineage antigen shared with normal dendritic cells and monocytes and NK-cells: HPA finds the gene group enriched in that blood lineage, and the 1 medicine aimed at it (Pentostatin) act on the wild-type protein, so the normal lineage is hit too. HPA ADA: RNA group enriched (intestine 454 nTPM, lymphoid tissue 228 nTPM); blood lineage group enriched (dendritic cells 211 nTPM, monocytes 351 nTPM, NK-cells 90 nTPM); no normal tissue stained high. Distribution: 1 cancer family in the corpus carries a prevalence row, label threshold or catalogue link for it (Leukaemia); Open Targets associates it with 0 specific cancer types at or above 0.5. (Rule 7 of scripts/fetch-target-specificity.ts.)","specificitySources":[{"label":"Human Protein Atlas ADA tissue","url":"https://www.proteinatlas.org/ENSG00000196839-ADA/tissue","note":"RNA tissue and blood lineage specificity, normal tissue antibody staining (version 25.1, CC BY-SA 3.0)"},{"label":"Human Protein Atlas ADA pathology","url":"https://www.proteinatlas.org/ENSG00000196839-ADA/pathology","note":"patients per staining level per cancer type (version 25.1, CC BY-SA 3.0)"},{"label":"Open Targets ENSG00000196839 associations","url":"https://platform.opentargets.org/target/ENSG00000196839/associations","note":"cancer associations at or above 0.5 (CC0)"}],"hgnc":"HGNC:186","ensembl":"ENSG00000196839","uniprot":"P00813","entrez":"100","firstDescribed":1983,"firstDescribedBasis":"sequence","firstDescribedNote":"Earliest sequence paper UniProt cites for the protein: Orkin S.H. et al, J. Biol. Chem, 1983, \"Molecular cloning of human adenosine deaminase gene sequences\".","firstDescribedSource":"https://pubmed.ncbi.nlm.nih.gov/6688808/","biology":"ADA is a zinc-dependent hydrolase expressed in most tissues and at high levels in lymphoid cells. Inhibiting it raises intracellular deoxyadenosine triphosphate, which blocks ribonucleotide reductase and DNA synthesis and triggers apoptosis, an effect most marked in lymphocytes with high deoxynucleoside kinase activity. Pentostatin binds the enzyme almost irreversibly; cladribine, the other purine analogue used in hairy cell leukaemia, is instead a substrate-resistant deoxyadenosine analogue.","whereFound":["Lymphocytes and lymphoid tissue (high)","Widely expressed in other tissues at lower levels","Also present in plasma as extracellular ADA"],"targetClass":"enzyme","prevalence":[{"cancerId":"metastatic-cancer","pct":"all","measure":"Housekeeping enzyme present in every dividing cell (purine breakdown, highest in lymphocytes); not a selection marker, which is why these drugs are given by cancer type rather than by test."}]},"route":"/targets/ada/","neighbours":{"cancer":[{"id":"cll","kind":"cancer","name":"Chronic lymphocytic leukaemia","route":"/cancers/cll/"},{"id":"hairy-cell-leukemia","kind":"cancer","name":"Hairy cell leukaemia","route":"/cancers/hairy-cell-leukemia/"}],"drug":[{"id":"pentostatin","kind":"drug","name":"Pentostatin","route":"/drugs/pentostatin/"}],"term":[{"id":"apoptosis","kind":"term","name":"Apoptosis","route":"/terms/apoptosis/"}]}}