PURIFICATION AND CHARACTERIZATION OF AN ADENOSINE CYCLIC 3'-5' MONOPHOSPHATE-DEPENDENT PROTEIN-KINASE FROM HUMAN ERYTHROCYTE-MEMBRANE

A cAMP dependent protein kinase was extracted from human erythrocyte membrane with hydrosoluble fraction and partially purified by ammonium sulfate-precipitation and DEAE-cellulose chromatography. The pH of optimal activity is 6.5; the enzyme has an absolute requirement of Mg2+ ions at the concentration of 10 mM and is strongly inhibited by Ca2+. It uses ATP as phosphate donor with a Km of 3.7 × 10-6 M. Cyclic AMP stimulates the activity with an apparent Ka of 5 × 10-8 M; cIMP and cGMP also acts as activators. Enzyme activity is thermolabile and not protected by Mg ATP complex. The enzyme purified from erythrocyte membrane is a type I protein-kinase as proven by DEAE cellulose chromatography and dissociation of the subunits in presence of NaCl 0.5 M and histone. © 1978.