Multiple forms of calf serum adenosine deaminase

Abstract

Adenosine deaminase has been purified from calf serum by ammonium sulfate fractionation and DEAE cellulose column chromatography. This purified serum deaminase is ultracentrifugally homogeneous with an S 20 value of 3.9. This value contrasts with the S 20 value of 2.15 for calf intestine adenosine deaminase. Electrophoresis of the purified serum adenosine deaminase results in the separation of the protein into two major and two minor protein bands. Assay of the enzyme directly on the electrophoresis strips shows that all four protein components have adenosine deaminase activity. Comparison of the electrophoretic properties of calf serum deaminase with calf intestine deaminase reveals that the two major deaminase bands from the serum have the same electrophoretic migrations as the two deaminase bands from the purified intestine enzyme. The largest amount of protein is associated with the fastest protein band of the serum deaminase and the slower component of the intestine deaminase. Heating the calf serum enzyme to 60 ° for short periods of time converts the slow-moving deaminase band to the fast deaminase band. The K m, V max, energy of activation, pH optimum, and substrate or inhibitor specificity were measured using the purified serum adenosine deaminase. These values were compared to those obtained for the intestine deaminase and are reported here.