– Phosphorylethanolamine (O-Phosphorylethanolamine) is a phosphomonoester metabolite of the phospholipid metabolism. Phosphorylethanolamine is a precursor of phospholipid synthesis and a product of phospholipid breakdown. Phosphomonoesters are present at much higher levels in the brain than in other organs. In developing the brain, phosphomonoesters are normally elevated during the period of neuritic proliferation. This also coincides with the occurrence of normal programmed cell death and synaptic pruning in developing the brain. These findings are consistent with the role of phosphomonoesters in membrane biosynthesis. Phosphorylethanolamine shows a strong structural similarity to the inhibitory neurotransmitter, GABA, and the GABAB receptor partial agonist, 3-amino-propylphosphonic acid. Phosphorylethanolamine is a phosphomonoester which is decreased in post-mortem Alzheimer’s disease (AD) brain.