Abstract

CDP-ethanolamine:diacylglycerol ethanolaminephosphotransferase (EPT) catalyzes the transfer of phosphoethanolamine from CDP-ethanolamine to diacylglycerol to produce phosphatidylethanolamine (PE). To date, the dual specificity of choline/ethanolaminephosphotransferase (CEPT) has been recognized as the total activity responsible for the synthesis of PE via the CDP-ethanolamine pathway in human. We report here the identification and characterization of another human cDNA that encodes CDP-ethanolamine-specific human EPT (hEPT1). Through homology search, we found that human selenoprotein I contained the CDP-alcohol phosphatidyltransferase signature, a common motif conserved in phospholipid synthases. Bacterial expression of the cDNA in Escherichia coli demonstrated that the product specifically used CDP-ethanolamine as the phosphobase donor to produce PE with the activation by both Mn(2+) and Mg(2+). RT-PCR and Northern blot analysis revealed that hEPT1 was ubiquitously expressed in multiple tissues, but in brain it was highly expressed in cerebellum. Here, we propose that in addition to previously identified CEPT, hEPT1 is involved in the biosynthesis of PE via the Kennedy pathway.