Protein kinases of Dictyostelium discoideum, strain AX-2

In cell homogenates of Dictyostelium discoideum, strain AX-2, four major soluble protein kinases (ATP:protein phosphotransferase, EC 2.7.1.37) and one membrane-associated protein kinase activity were identified. The enzymes showed high affinity for casein. One of the enzymes was purified by affinity chromatography on casein-coated Sepharose. The soluble high molecular weight enzymes phosphorylated histones, whereas the low molecular weight enzymes did not. The same protein kinase species were present in vegetative and aggregation-competent cells. Their specific activity, however, changed during the development to aggregation competence. None of the enzymes was stimulated by cyclic AMP or cyclic GMP, regardless of their origin from vegetative or aggregation-competent cells.