A method of changing or otherwise converting the biological activity of a PKC peptide agonist to a peptide antagonist is described. The method involves substituting one or more amino acid residues so as to effect a change in charge in the peptide and/or to otherwise make the sequence similar to a sequence derived from the PKC binding site on the RACK protein for the respective PKC enzyme. Methods of inhibiting the activity of a PKC enzyme, and various peptide antagonists of εPKC are also disclosed.