# Adenosine deaminase (ADA)

Source: https://onco.cc/targets/ada/  
OnCo record `ada` (Target). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

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.

## Fields

- Kind: Target
- Last checked: 2026-09-04
- Symbol: ADA
- Class: enzyme
- 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.
- Where found: Lymphocytes and lymphoid tissue (high); Widely expressed in other tissues at lower levels; Also present in plasma as extracellular ADA

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Adenosine_deaminase
- UniProt P00813: ADA: https://www.uniprot.org/uniprotkb/P00813/entry
- HGNC:186 ADA: https://www.genenames.org/data/gene-symbol-report/#!/hgnc_id/HGNC:186

## Connected records

- cancers: [Chronic lymphocytic leukaemia](https://onco.cc/cancers/cll/), [Hairy cell leukaemia](https://onco.cc/cancers/hairy-cell-leukemia/)
- drugs: [Pentostatin](https://onco.cc/drugs/pentostatin/)
- terms: [Apoptosis](https://onco.cc/terms/apoptosis/)

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JSON: https://onco.cc/api/v1/entities/ada.json