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In [[enzymology]], a '''ceramide phosphoethanolamine synthase''' ([[Enzyme Commission number|EC]] 2.7.8.-) is an [[enzyme]] that [[Catalysis|catalyzes]] the [[chemical reaction]]

:a [[ceramide]] + a phosphoethanolamine head group donor <math>\rightleftharpoons</math> a ceramide-phosphoethanolamine + side product

[[Ceramide phosphoethanolamine]] (CPE) is a [[sphingolipid]] consisted of a [[ceramide]] and a [[phosphatidylethanolamine]]. Thus, this class of enzymes uses ceramide and a donor molecule for phosphoethanolamine as [[substrate (biochemistry)|substrate]]s to produce a ceramide phosphoethanolamine and a side product. The head group donor for phosphoethanolamine can be either [[phosphatidylethanolamine]] or [[CDP-ethanolamine]], thus the side product is either a [[1,2-diacylglycerol]] or a [[Cytidine monophosphate|CMP]], respectively.

This enzyme belongs to the family of [[transferase]]s, specifically those transferring non-standard substituted [[phosphate]] groups.

==Mammalian Ceramide Phosphoethanolamine Synthases==
In [[mammals|mammalian cells]], two [[Ceramide phosphoethanolamine|CPE]] synthase activities have been described, one resides in the [[endoplasmic reticulum]], and the other one is associated with the [[plasma membrane]].<ref>Malgat, M., Maurice, A., and Baraud, J. (1986) Sphingomyelin and ceramide-phosphoethanolamine synthesis by microsomes and plasma membranes from rat liver and brain. J. Lipid Res. 27, 251–260</ref><ref>Malgat, M., Maurice, A., and Baraud, J. (1987) Sidedness of ceramidephosphoethanolamine synthesis on rat liver and brain microsomal membranes. J. Lipid Res. 28, 138–143</ref><ref>Maurice, A., Malgat, M., and Baraud, J. (1989) Sidedness of ceramidephosphoethanolamine synthesis on rat liver plasma membrane. Biochimie 71, 373–378</ref><ref name = "Ternes2009">Ternes, P., Brouwers, J. F., van den Dikkenberg, J., and Holthuis, J. C. (2009) Sphingomyelin synthase SMS2 displays dual activity as ceramide phosphoethanolamine synthase. J. Lipid Res. 50, 2270–2277</ref><ref name = "Vacaru2009">Vacaru, A. M., Tafesse, F. G., Ternes, P., Kondylis, V., Hermansson, M., Browers, J. F. H. M., Somerharju, P., Rabouille, C., and Holthuis, J. C.(2009) Sphingomyelin synthase-related protein SMSr controls ceramide homeostasis in the ER. J. Cell. Biol. 185, 1013–1027</ref> The endoplasmic reticulum-resident CPE synthase, SMSr, is identified as a monofunctional CPE synthase produces trace amounts of CPE.<ref name="Ternes2009" /><ref name="Vacaru2009" /> On the other hand, mammalian CPE synthase that is on the [[plasma membrane]], [[Sphingomyelin synthase|SMS2]], is a bifunctional enzyme that produces both CPE and [[sphingomyelin]], thus also functioning as a [[sphingomyelin synthase]].<ref name="Ternes2009" /> Both mammalian CPE synthases, [[Sphingomyelin synthase|SMS2]] and SMSr, use [[phosphatidylethanolamine]] (PE) as head group donor and catalyzes the reaction

:a [[ceramide]] + a [[phosphatidylethanolamine]] <math>\rightleftharpoons</math> a ceramide-phosphoethanolamine + [[1,2-diacylglycerol]]

==Invertebrate Ceramide Phosphoethanolamine Synthases==
SMSr protein is found in all organisms throughout the animal kingdom as a CPE synthase, yet it produces trace amounts of CPE.<ref name="Vacaru2009" /><ref name="Vacaru2013" /> [[Drosophila]] and a group of [[invertebrates]] lack [[Sphingomyelin synthase|SMS2]] [[homology (biology)|homologues]].<ref name="Vacaru2009" /><ref name = "Vacaru2013">Vacaru AM, van den Dikkenberg J, Ternes P, Holthuis JC. Ceramide phosphoethanolamine biosynthesis in Drosophila is mediated by a unique ethanolamine phosphotransferase in the Golgi lumen. J Biol Chem. 2013 Apr 19;288(16):11520-30. doi: 10.1074/jbc.M113.460972. Epub 2013 Feb 28. PubMed PMID 23449981; PubMed Central PMCID: PMC3630839</ref> This group of invertebrates synthesizes CPE using a particular enzyme called CPES.<ref name="Vacaru2013" /> CPES uses [[CDP-ethanolamine]] rather than phosphatidylethanolamine as head group donor, thus catalyzes the reaction <ref name="Vacaru2013" />

:a [[ceramide]] + a [[CDP-ethanolamine]] <math>\rightleftharpoons</math> a ceramide-phosphoethanolamine + [[Cytidine monophosphate|CMP]]

CPES uses a different reaction mechanism than the one [[sphingomyelin synthase]] uses, but very similar to that of enzymes involved in [[Biosynthesis|synthesis]] of phosphatidyl ethanolamine ([[Enzyme Commission number|EC]] 2.7.8.1) via the [[Kennedy pathway]].<ref>KENNEDY EP, WEISS SB. The function of cytidine coenzymes in the biosynthesis of phospholipides. J Biol Chem. 1956 Sep;222(1):193-214. PubMed PMID 13366993.</ref>

==References==
{{reflist}}

[[Category:Chemical reactions]]
[[Category:EC 2.7.8]]
[[Category:Lipids]]

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