Ethanolaminephosphotransferase that catalyzes the transfer of phosphoethanolamine (PE) from CDP-ethanolamine to lipid acceptors, the final step in the synthesis of PE via the 'Kennedy' pathway (PubMed:17132865, PubMed:28052917, PubMed:29500230). PE is the second most abundant phospholipid of membranes in mammals and is involved in various membrane-related cellular processes (PubMed:17132865). The enzyme is critical for the synthesis of several PE species and also catalyzes the synthesis of plasmanyl-PE, a lipid required for proper myelination and neurodevelopment, from 1-alkyl-2-acylglycerol (PubMed:29500230). {ECO:0000269|PubMed:17132865, ECO:0000269|PubMed:28052917, ECO:0000269|PubMed:29500230}. This is the function of ENSG00000138018 (SELENOI, selenoprotein I).