ADA

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The ADA gene at 20q13.12 codes for the 363 amino acid enzyme adenosine deaminase. This catalyzes the hydrolytic deamination of adenosine and 2-deoxyadenosine so playing a key role in purine metabolism. It modulates signaling by extracellular adenosine, and acts as a positive regulator of T-cell coactivation, by binding dipeptidyl peptidase 4. Other roles involve its actions as a positive modulator of adenosine receptors A, stimulation of plasminogen activation, a role in male fertility and protection in early postimplantation embryonic development. It was the target of the first gene therapy experiments in man as mutations causing failure to function result in a form of severe combined immunodeficiency (ADA-SCID, OMIM:102700) and partial immune deficiency can result from other mutations. Treatment of these forms of SCID is with either:

  1. Bone marrow transplantation (limited by suitable donors)
  2. Weekly infusions of adenosine deaminase
  3. Strimvelis, with this gene therapy offering a 75% chance as of 2016 when first licensed of complete cure (for up to 13 years).