ADA specific activity and substrate levels after neonatal BMT. ADA enzyme specific activity (nmol of adenosine converted to inosine/min/mg protein) was determined in tissue lysates.¹²  Age-matched, Ada^+/+ congenic controls were compared at day 16 (n = 4) and day 60 (n = 2) to untreated Ada^−/− mice (n = 3) and Ada^−/− treated with neonatal BMT at day 16 (n = 3) and day 60 (n = 6) and to Ada^−/− mice receiving ERT with PEG-ADA at day 16 (n = 2) and at day 60 (n = 2). ADA specific activity in the thymus (A), spleen (B), lung (C), and liver (D). ADA substrate concentrations (nmol/mg protein) of adenosine and deoxyadenosine in thymus (E), spleen (F), lung (G), and liver (H).