Protein kinase activity associated with the surface of guinea pig macrophages.

Abstract

Protein kinase activity has been detected associated with the outer surface of guinea pig peritoneal macrophages. Macrophages incubated with [gamma-32P]ATP incorporated 32P-phosphate into cell-associated proteins. Inorganic phosphate did not compete, nor could inorganic [32P]phosphate substitute as the phosphate donor, demonstrating that transfer of phosphate from ATP to protein is direct and extracellular. The macrophage-associated protein kinase was also shown to phosphorylate added acceptor protein (histone) and to be tightly associated with the cell surface. Thus, a new ectoenzyme, a protein kinase, has been detected in macrophages.