A protein kinase C‐related enzyme activity in Dictyostelium discoideum

Abstract
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 Ca2+, 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 Ca2+. The D. discoideum enzyme was strongly stimulated by nanomolar concentrations of PMA, and inhibited by PKC‐inhibitor staurosporine.