Synaptosomal phospholipase D: potential role in providing choline for acetylcholine synthesis

The synaptic membrane (SM) prepared from rat brain synaptosomes displayed the highest activity of phospholipase D of mammalian tissue thus far observed. In common with the previously described latency of the microsomal enzyme, the SM phospholipase D (PLD) activity is barely detectable in the absence of 4 mM sodium oleate. Incubation of synaptosomes in the presence of choline labelled lecithin, sodium oleate and acetyl CoA resulted in the formation of a product co-chromatographing with acetylcholine. The potential role of SM PLD liberating choline from lecithin into the synaptic cleft is discussed in relationship to acetylcholine formation.