Phosphoethanolamine

Fig. 1. Chemical stmcture of phosphatidylcholine (PC) (1) and other related phosphohpids. R C O represents fatty acid residues. The choline fragment may be replaced by other moieties such as ethanolamine (2) to give phosphatidylethanolamine (PE), inositol (3) to give phosphatidylinositol (PI), serine (4), or glycerol (5). IfH replaces choline, the compound is phosphatidic acid (6). The corresponding lUPAC-lUB names ate (1), l,2-diacyl-t -glyceto(3)phosphocholine (2), l,2-diacyl-t -glyceto(3)phosphoethanolamine (3), 1,2-diacyl-t -glyceto(3)phosphoinositol (4), 1,2-diacyl-t -glyceto(3)phospho-L-serine and (5), l,2-diacyl-t -glyceto(3)phospho(3)-t -glycetol.

Dilauroyl-sn-glycero-3-phosphoethanolamine ( -dilauroyl-a-cephalin, 3-sn-phosphat-idylethanolamine 1,2-didodecanoyl) [59752-57-7] M 579.8, m 210 , pKes,(d (PO4H), PKes,(2) 10.5 (NH2). Recrystd from EtOH or tetrahydrofuran. [Bevan and Malkin J Chem Soc 2667 /95/ IR Bellamy and Beecher7 Chem Soc 728 1953.]... 

Phosphatidylethanolamine synthesis begins with phosphorylation of ethanol-amine to form phosphoethanolamine (Figure 25.19). The next reaction involves transfer of a cytidylyl group from CTP to form CDP-ethanolamine and pyrophosphate. As always, PP, hydrolysis drives this reaction forward. A specific phosphoethanolamine transferase then links phosphoethanolamine to the diacylglycerol backbone. Biosynthesis of phosphatidylcholine is entirely analogous because animals synthesize it directly. All of the choline utilized in this pathway must be acquired from the diet. Yeast, certain bacteria, and animal livers, however, can convert phosphatidylethanolamine to phosphatidylcholine by methylation reactions involving S-adenosylmethionine (see Chapter 26). 

Vitamins and lipids are often required for animal cells to grow in serum-free medium. Phosphoethanolamine and ethanolamine are key additives that facilitate the growth of the mammary tumor cell line 64024 (Kano-Sueoka and Errick, 1981). In addition, ethanolamine promotes the growth of human lymphocytes and mouse hybridoma cells. Short-term cultures of human diploid lung and foreskin fibroblasts grow in medium that includes among its supplements soybean lecithin, cholesterol, sphingomyelin, and vitamin E. 

Kano-Sueoka, T. Errick, J.E. (1981). Effects of phosphoethanolamine and ethanolamine on growth of mammary carcinoma cells in culture. Exp. Cell Res. 136, 137-145. 

Pessi, G Kociubinski, G. Ben Mamoun, C. A pathway for phosphatidylcholine biosynthesis in Plasmodium falciparum involving phosphoethanolamine methyla-tion. Proc. Nat. Acad. Sci. USA 2004,101, 6206-6211. 

Recently, a series of soluble phospholipids with n-hexanoyl side chains and a variety of headgroups were assayed as substrates for PLCBc [37]. The results (Table 4) indicate that both l,2-dihexanoyl-s -glycero-3-phosphocholine (C6PC) and l,2-dihexanoyl-sn-glycero-3-phosphoethanolamine (C6PE) are processed with similar catalytic efficiencies (kcaXIKm) by the enzyme, while 1,2-dihe-... 

Figure 1. Synthetic pathway for PS and PE in mammalian cells. The major steps occuring in the synthesis and interconversion of PS and PE are shown. The PS synthases condense serine with a phosphatidyl moiety derived from PC and PE. The nascent PS can be converted to PE by decarboxylation. PE can also be formed by transfer of a phosphoethanolamine moiety from CDP-ethanolamine to diacylglycerol via the Kennedy pathway. The abbreviations used are PC, phosphatidylcholine PS, phosphatidylserine PE, phosphatidylethanolamine DG, diacylglycerol PSD, phosphatidylserine decarboxylase PSS, PS synthase.

The majority of PC is synthesized in mammalian cells by the CDP-choline or Kennedy pathway in the endoplasmic reticulum (Eigiue 1). In this pathway, choline taken up from the external medium or released in the cytosol by breakdown of choline containing compoimds, is first converted to phosphocholine by the enzyme choline kinase (CK) (Ishidate, 1997). There are two isoforms of CK cloned which both can convert also ethanolamine to phosphoethanolamine, albeit with a lesser affinity (Aoyama et al 2000). Alternatively phosphocholine can be generated by enzymes that preferentially phosphorylate ethanolamine and are therefore designated ethanolamine kinases (EK). As yet also two different EKs are known (EKI 1 and 2 Lykidis etal., 2001). 

PE can be generated by several mechanisms. The CDP-ethanolamine route may be important under physiological conditions in vivo when an abundant supply of ethanolamine is present. The CDP-ethanolamine pathway is very similar to the CDP-choline pathway described above (Tijburg et al. 1989 Bladergroen and Van Golde, 1997). The pathway comprises (i) an ethanolamine kinase (EK) which converts ethanolamine to phosphoethanolamine, (ii) an CTP phosphoethanolamine cytidyltransferase... 

Figure 3 Design of a diepitope liposomal construct. Small unilamellar liposomes (PC/PG/Chol 55/25/50 molar ratio diameter 100nm) containing 10mol% of bromo-acetyl l,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine and 10mol% of the thiol-reactive lipopeptide adjuvant anchor Pam3CysAlaGly-Mal were reacted, at 25°C successively at pH 6.5, with the T-helper epitope QYI, derivatized with a C-linker at its N-terminus, followed at pH 9.0 by the B-epitope TPE derivatized with a CG linker at its N-terminus. Abbreviations PC, phosphatidylcholine PE, phosphatidylethanolamine SUV, small unilamellar vesicles. Source From Refs. 11, 20, 21.

The choice of commercially available PEG-lipids is ultimately quite reduced. The mainly reported ones are the anionic polyethylene glycol-phosphoethanolamine (PEG-PE) and the neutral PEG-ceramide (Fig. 1). 

Scheme 4 Structure of the native GPI anchor of human erythrocyte acetylcholineesterase, divided into three main parts the phosphoethanolamine linker (red), the glycan core (black), and the phospholipid tail (green).

This enzyme [EC 3.3.2.5], also known as lysoplasmalo-genase, catalyzes the hydrolysis of l-(l-alkenyl)-sn-glyc-ero-3-phosphoethanolamine to yield an aldehyde andxn-glycero-3-phosphoethanolamine. 

This enzyme [EC 3.1.4.39], also known as alkylglycero-phosphoethanolamine phosphodiesterase, catalyzes the hydrolysis of l-alkyl-sn-glycero-3-phosphoethanolamine to produce 1-alkyl-xn-glycerol 3-phosphate and ethanol-amine. The enzyme will also act on the acyl and choline analogs of the lipid. 

Acyl-sn-glycero-3-phosphoethanolamine, LYSOPHOSPHOLIPASE D Acyl halide reduction to alcohols (or aldehydes),... 

NBDPE 1,2-dipalmitoyl-sn-glycero-3-( A-(7-nitro-2-l, 3-benzooxa-diazol-4-yl))-phosphoethanolamin... 

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