Abstract
5'-Adenylic acid deaminase free from sodium and potassium ion is prepared from erythrocytes by a convenient method. Like adenosine triphosphatase and adenylic kinase from erythrocytes, the deaminase is activated by some monovalent cations, but unlike these enzymes it requires the presence of a monovalent cation. In all three instances the pattern of activation by ions is similar and suggests a common mechanism.