ADA2 is a lysosomal deoxyadenosine deaminase acting on DNA involved in regulating TLR9-mediated immune sensing of DNA.

Although adenosine deaminase 2 (ADA2) is considered an extracellular ADA, evidence questions the physiological relevance of this activity. Our study reveals that ADA2 localizes within the lysosomes, where it is targeted through modifications of its glycan structures. We show that ADA2 interacts with DNA molecules, altering their sequences by converting deoxyadenosine (dA) to deoxyinosine (dI).