[Serum 2'deoxyadenosine/adenosine deaminase ratio in clinical diagnosis].

: In humans Adenosine Deaminase activity (ADA) differs in serum and tissues in pH optimum, Km, and relative substrate specificity. Thus, on the basis of a major or a minor activity on 2'Deoxyadenosine, a "serum type"enzyme can be distinguished from a "tissue type" enzyme. The examination of ADA or relative substrate specificity (ratio 2'Deoxyadenosine/adenosine deaminase) in the serum of 174 patients with variant pathology, revealed the occurrence of a "tissue type" enzyme in sera of acute Lymphoblastic Leukaemia patients.