Ethanolamine phosphotransferase

It is postulated that inhibition of PtdCho synthesis and the release of choline are key steps associated with excitotoxicity and are common to NMDA and AMPA receptor stimulation. The mechanism of inhibition of PtdCho is not fully understood. Metabolic labeling experiments in cortical cultures demonstrate that NMDA receptor over activation does not modify the activity of phosphochohne or phospho-ethanolamine cytidylyltransferases but strongly inhibits choline and ethanolamine phosphotransferase activities. This effect is observed well before any significant membrane damage and cell death. Moreover, cholinephosphotransferase activity is lower in microsomes from NMDA-treated cells. These results show that membrane... 

Gasull T., Sarri E., DeGregorio-Rocasolano N., and Trullas R. (2003). NMDA receptor overactivation inhibits phospholipid synthesis by decreasing choline-ethanolamine phosphotransferase activity. J. Neurosci. 23 4100 1107. 

Fig. 7. Biosynthesis of choline plasmalogens (plasmenylcholines) via modification of the sn-3 polar head group of ethanolamine plasmalogens (plasmenylethanolamines). These reactions are proposed to be catalyzed directly by (1) a base exchange enzyme or (II) At-methyltransferase. A combination of other enzymatic reactions could also result in replacement of the ethanolamine moiety of plasmenylethanolamine to produce plasmenylcholines the enzymes responsible include (IB) phospholipase C, (IV) the reverse reaction of ethanolamine phosphotransferase, (V) phospholipase D, (VI) phosphohydtolase, and (VII) cholinephosphotransferase. AdoMet, 5-adenosyl-L-methionine AdoHcy, 5-adenosyl-L-homocysteine Etn, ethanolamine GPE, sn-glycero-...

Faulkner, A. Turner, J.M. Phosphorylation of ethanolamine in catabolism biodegradative adenosine triphosphate-ethanolamine phosphotransferase and related enzymes in baecteria. Biochem. Soc. Trans., 2, 133-137 (1974)... 

Choline phosphotransferase (EC 2.7.8.2) and ethanolamine phosphotransferase (EC 2.7.8.1) are located in the endoplasmic reticulum and catalyse the final step in the CDP-base pathway (Figs 11.13 and 11.14). Although several early workers claimed that the two activities were present on the same protein it now seems reasonably certain that separate base phosphotransferases are present in animal tissues (cf. Bell and Coleman, 1980). Although the evidence is less good, the same appears true in plant tissues (Harwood, 1979). Small amounts of the base... 

Glyceride and phospholipid metabolism Glycetol-3-phosphate dehydrogenase Phosphatidate phosphatase Ethanolamine phosphotransferase Choline phosphotransferase Ceramide choline phosphotransferase... 

Figure 2.11. Lipid synthesis. GDP = glycerol-3-phosphate dehydrogenase. PP = phosphat-idate phosphatase. CPT=choline phosphotransferase. BPT= ethanolamine phosphotransferase. AC = acetyl CoA carboxylase. HAD 3-hydroxyacyl-CoA dehydrogenase. CCPT = cemmide choline phosphotransferase. HMGR = hydroxymethyl utaryl-CoA reductase. MK = mevalonate kinase. IPPI = isopentenyl pyrophosphate isomerase...

L-Serine kinase, L-serine-3-phosphate decarboxylase 2 phosphoethanolamine phosphatase 3 ethanolamine kinase 4 phosphocholine phosphatase 5 choline kinase 6 ethanolamine phosphate cytidylyltransferase 7 ethanolamine phosphotransferase (D 3.2.4), phosphatidyl ethanolamine methyltransferase, phospholipase D, choline kinase 8 choline phosphate cytidylyltransferase... 

The nucleotide pathway is the major pathway of phosphatidylethanolamine (PE) headgroup biosynthesis by plants (Sparace, et aL, 1981). It is catalyzed in sequence by ethanolamine kinase (EK), ethanolaminephosphate cytidylyltransferase (ECT) and ethanolamine phosphotransferase (EPT). EK has been characterized and purified from spinach leaves (Macher and Mudd, 1976) and soybean seeds (Williams and Harwood, 1994), EPT has been characterized in several plants (10), but little information is available about ECT. The only plant tissue in which ECT has been characterized is castor bean endosperm, where approximately 80% of the activity is in the outer mitochondrial membrane and the remainder in the endoplasmic reticulum (ER Wang and Moore, 1991). ECT is soluble in mammals and yeast (Sundler, 1975). 

The ER is the primary site for PE biosynthesis in this tissue (Sparace, et aL, 1981), and so the ER-bound ECT is a component of this synthesis. Mitochondrial ECT is too active to simply be supplying substrate to the ethanolamine phosphotransferase of that organelle. These points have been taken to indicate a function for the mitochondrial enzyme different from that of the ER, but that role remains undefined. For this reason we have examined the relative activities of the PE nucleotide synthesis pathway enzymes and partially purified the mitochondrial ECT. 

Wang and Moore (1991). Ethanolamine-phosphotransferase (EPT was measured as previously described (Sparace, etal, 1981). 

Ford, D.A., Rosenbloom, K.B. and Gross, R.W. (1992) The primary determinant of rabbit myocardial ethanolamine phosphotransferase substrate selectivity is the covalent nature of the sn-1 aliphatic group of diradyl glycerol acceptors. J. Biol. Chem. 267, 11222-11228. 

Figure 16.2 Pathways involved in the biosynthesis of ether-containing lipids. The enzymes that may be involved in nonselective utilization of acyl CoA pool are highlighted with broken-lined arrows. The formed ether-containing lipids are highlighted with light gray. The symbol of stands for CDP-ethanolamine l-0-alkyl-2-acyl-sn-glycerol ethanolamine phosphotransferase or CDP-choline 1 -O-alkyl-2-acyl-in-glycerol chohne phosphotransferase. DHAP denotes dihydroxyacetone phosphate. AU other abbreviations can be found in the list of abbreviations.

Glycerolipidic metabolism in olive tree is affected by the calcium chloride action. It exerces an inhibitory effect on the phospholipids biosynthesis enz3mies and particularly on CDP-choline and CDF-ethanolamine phosphotransferases (5,6). Phospholipids acylation reactions are widely dropped in favour of neutral lipids at increasing CaCl2 levels (6). 

Phosphatidylethanolamine can also be formed by an analogous series of reactions to phosphatidylcholine that is by the successive actions of ethanolamine kinase, ethanolamine phosphate cytidylyltransferase and ethanolamine phosphotransferase (Figure 7.1). As in the synthesis of phosphatidylcholine, the activity of the cytidyltransferase appears to be rate limiting for phosphatidylethanolamine synthesis and also the final enzyme, the ethanolamine phosphotransferase, catalyses a freely reversible reaction. 

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