CDP-ethanolamine:1,2-diacylglycerol ethanolaminephosphotransferase

Abstract

Ethanolaminephosphotransferase catalyzes the final step of the CDP-ethanolamine pathway for the de novo synthesis of phosphatidylethanolamine (PtdEtn) via transfer of a phosphoethanolamine moiety from CDP-ethanolamine to diacylglycerol for the formation of PtdEtn and CMP. Ethanolaminephosphotransferase is an integral membrane-bound enzyme whose intracellular location defines the site of PtdEtn synthesis by the CDP-ethanolamine pathway. Subcellular fractionation experiments have yet to resolve the precise subcellular location of ethanolaminephosphotransferase, although it is routinely associated with the microsomal fraction. Ethanolaminephosphotransferase has yet to be purified from any source and its cDNA has not been isolated from any mammalian source, thus preventing the generation of antibodies necessary to directly examine its intracellular location through immunofluorescence or electron microscopy approaches. An ethanolaminephosphotransferase gene has recently been isolated from the yeast Saccharomyces cerevisiae and structure/function analyses of the encoded enzyme identified several important characteristics including the catalytic site. The predicted amino acid sequence of the S. cerevisiae ethanolaminephosphotransferase gene should allow for the generation of antibodies required to directly define the site of PtdEtn synthesis in this organism, and it has provided the necessary information to pursue the isolation of a mammalian cDNA.