Inhibition of protein kinase C by semisynthetic phospholipid plasmanyl-(N-acyl)-ethanolamine, a nontoxic antitumor preparation.

Protein kinase C was extracted from mouse brain and partially purified by ion-exchange chromatography on a DEAE-cellulose column. Its activity was determined by incorporation of phosphate from [gamma-32P]ATP into histone H2b. The semisynthetic alkyl-phospholipid plasmanyl-(N-acyl)-ethanolamine (PNAEs) with selective antitumor activity inhibited the activity of the protein kinase in a cell-free system in the presence of phosphatidylserine, a protein kinase C activator. The inhibition was competitive with respect to phosphatidylserine, the inhibition constant being 40 microM.