Horibata Yasuhiro, Hirabayashi Yoshio
Neuronal Circuit Mechanisms Research Group, Brain Science Institute, RIKEN, Hirosawa 2-1, Wako-shi, Saitama 351-0198, Japan.
J Lipid Res. 2007 Mar;48(3):503-8. doi: 10.1194/jlr.C600019-JLR200. Epub 2006 Nov 28.
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.
二酰基甘油乙醇胺磷酸转移酶（EPT）催化磷酸乙醇胺从胞苷二磷酸乙醇胺转移至二酰基甘油，以生成磷脂酰乙醇胺（PE）。迄今为止，胆碱/乙醇胺磷酸转移酶（CEPT）的双重特异性已被认为是人类通过胞苷二磷酸乙醇胺途径合成PE的全部活性。我们在此报告另一种编码胞苷二磷酸乙醇胺特异性人类EPT（hEPT1）的人类cDNA的鉴定与表征。通过同源性搜索，我们发现人类硒蛋白I含有胞苷二磷酸醇磷脂转移酶特征序列，这是磷脂合成酶中保守的一个共同基序。该cDNA在大肠杆菌中的细菌表达表明，其产物特异性地使用胞苷二磷酸乙醇胺作为磷酸碱基供体来生成PE，且受到Mn(2+)和Mg(2+)两者的激活。逆转录聚合酶链反应（RT-PCR）和Northern印迹分析显示，hEPT1在多种组织中普遍表达，但在脑中，它在小脑中高度表达。在此，我们提出，除了先前鉴定的CEPT外，hEPT1也通过肯尼迪途径参与PE的生物合成。
