Activation of N-acylethanolamine-releasing phospholipase D by polyamines

N-acylethanolamines including anandamide (an endogenous ligand of cannabinoid receptors) are biosynthesized from N-acyl-phosphatidylethanolamine (PE) by a phosphodiesterase of the phospholipase D type. The enzyme partially purified from the particulate fraction of rat heart hydrolyzed N-palmitoyl-PE to N-palmitoylethanolamine with a specific activity of 50 nmol/min per mg protein at 37 degrees C in the presence of 10 mM CaCl2. We found that the enzyme was highly activated in dose-dependent manner by polyamines like spermine, spermidine, and putrescine. Spermine was the most potent with an EC50 value around 0.1 mM, and increased the specific enzyme activity 27 fold up to 53 nmol/min per mg protein. However, a synergistic effect of spermine and the known activator (Ca2+ or Triton X-100) was not observed. The spermine-stimulated enzyme was also active with N-arachidonoyl-PE (a precursor of anandamide). Thus, polyamines may function as endogenous activators to control the biosynthesis of anandamide and other N-acylethanolamines.