In crude cell lysates of the cellular slime mould Dictyostelium discoideum we identified a protein kinase C (PKC)-like enzyme activity. This activity, measured as phosphorylation of a synthetic EGF-receptor-derived peptide [(1987) J. Biol. Chem. 262, 772-777], was regulated by Ca 2+, phosphatidylserine (PS), 1,2-dioleoyl-rac-glycerol (DG) and the phorbol ester PMA. PS and DG stimulated the enzyme in a synergistic manner. The stimulation by these lipids was, in contrast to what has been found for 'classical' mammalian PKC, not dependent on Ca 2+. The D. discoideum enzyme was strongly stimulated by nanomolar concentrations of PMA, and inhibited by PKC-inhibitor staurosporine.Protein kinase C; Chemotactic receptor; cAMP receptor; (Dictyostelium discoideum)