[Adenosine deaminase activity in human erythrocytes and lymphocytes]

A radiochromatographic method is described for measuring enzymatic activity of adenosine deaminase in human erythrocytes and lymphocytes. [8-14C]-adenosine is converted into inosine and hypoxanthine; after chromatographic separation of the products, the radioactivity is determined. The kinetic properties of the enzyme have been studied. The Km values for the erythrocyte and lymphocyte enzymes are higher as compared with purified deaminase. Optimum conditions for substrate concentration for assay were established. The mean normal activity (+/- S.E. of mean) is: for erythrocytes, 494 +/- 61; nmol min-1 ml-1; for lymphocytes- 147 +/- 0.18 nmol min-1 10(6) cellules. The mean values are higher than that given by other methods working at a lower (non-staurating) substrate concentration.