Inter-relationships of ethanolamine glycerophospholipid and sphingolipid pathways. The boxed reactions are conducted in peroxisomes while the other reactions are mainly in the endoplasmic reticulum. Red lipids are decreased in Alzheimer's disease brain while blue lipids are increased. The same color scheme is used for the tabular presentation of the various enzymes involved in glycerophospholipid and sphingolipid metabolism. CDP-ethanolamine from sphingolipid metabolism could provide the charged base for synthesis of ethanolamine plasmalogens. CDP, cytidine-diphosphate; CDP-E, cytidine-diphosphate ethanolamine; DHAP, dihydroxyacetone phosphate; GP, glycerolphosphate; GPC, glycerophosphocholine; GPE, glycerophosphoethanolamine; PE, phosphoethanolamine; S-1-P, sphingosine-1-phosphate; Sa-1-P, sphinganine-1-P.