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PubMed1979

Quantitative evaluation of two pathways for ethanolamine phosphoglyceride biosynthesis in rat brain in vivo.

[3H]Ethanolamine and [32P]orthophosphate were injected intraventricularly into adult female rats. At varying time intervals after the injection (1--10 min), the animals were killed by means of a microwave apparatus, and phosphorylethanolamine and ethanolamine phosphoglycerides were extracted from the brains and counted after separation. The kinetic constants for phosphorylethanolamine incorporation into ethanolamine lipids were calculated both from 3H data and from 32P data. From our results, it seems that base exchange reactions for ethanolamine incorporation into ethanolamine lipids are a pathway active in brain in vivo.

Animals↗
PubMed1979

Lipid metabolism in germinating seeds. Purification of ethanolamine kinase from soya bean.

Ethanolamine kinase has been purified to homogeneity from germinating soya bean (Glycine max L.) seeds. The purified enzyme had a molecular weight of 17--19 000 as estimated by gel filtration and sodium dodecyl suphate-polyacrylamide gel electrophoresis. It would not phosphorylate choline, had a Km for ethanolamine of 8 microM and utilised Mg-ATP. The kinase could be purified in a 37 000 molecular weight form (dimer) which would easily dissociate on storage. In contrast to ethanolamine kinase whose activity was unaffected by the presence of choline in the assay system, soya bean choline kinase, although not phosphorylating ethanolamine, was competitively inhibited by the latter. The purification of specific choline and ethanolamine kinases from germinating soya bean confirmed in vivo observations which had indicated separate enzymes.

Choline↗
PubMed1994

Molecular species of ethanolamine plasmalogens and transacylase activity in rat tissues are altered by fish oil diets.

Effects of dietary fish oil ethyl esters and alkyldiacetylglycerols (an ether-linked lipid) on the distribution of subclasses of choline- and ethanolamine-glycerophospholipids as well as effects on highly unsaturated molecular species of ethanolamine plasmalogens from brain, spleen, kidney, lung, and testis of rats were examined. Supplementation of ethyl ester concentrates of n-3 fatty acids had no effect on the distribution of subclasses in any of the tissues. However, the supplements of 1-O-octadec-9'-enyl-2,3-diacetyl-sn-glycerol (diacetates of selachyl alcohol) caused significant increases in the alkylacylglycerophosphocholine and alkylacylglycerophosphoethanolamine subclasses from spleen and lung and in the alkylacylglycerophosphoethanolamine subclass from kidney. Dietary supplements of fish oil ethyl esters reduced the arachidonate-containing species of ethanolamine plasmalogens whereas molecular species having 20:5(n-3), 22:6(n-3), and/or 22:5(n-3) acyl groups were increased in the spleen, lung, and kidneys, but not brain. In testicular tissue from rats fed the fish oil diets, the molecular species of ethanolamine plasmalogens containing 22:5(n-6) acyl groups were reduced. An increase of ethanolamine plasmalogens with 18:1 alk-1-enyl moieties paired with highly unsaturated sn-2 acyl groups were found in the tissues of rats fed the fish oil plus selachyl alcohol diacetate supplements. Rats on the diet containing fish oil ethyl esters had significantly lower [3H]alkyllysoglycerophosphocholine CoA-independent transacylase activity in spleen microsomes than controls. This suggests that supplements of n-3 fatty acids interferes with the transacylation of arachidonate, an event that could seriously impair the release of arachidonate and lysophospholipids (e.g., lyso-PAF) that are precursors of potent bioactive lipid derivatives.

Acyltransferases↗
PubMed1977

Biosynthesis of rat brain phosphatidylethanolamines from intracerebrally injected ethanolamine.

[2-3H]Ethanolamine was injected intracerebrally into male rats and the brains of the animals immediately removed by particular procedures at regular intervals over the first 1200 sec. The incorporation of radioactivity into brain phosphorylethanolamine, cytidine-5'-diphosphate (CDP) ethanolamine and phosphatidylethanolamines was examined and quantitated. The nature of phosphatidylethanolamine molecular subspecies, which became labelled, was also investigated after isotope administration. Phosphorylethanolamine, CDP-ethanolamine and phosphatidylethanolamines were all labelled already 5 sec after the administration of labelled ethanolamine. The specific radioactivities of different phosphatidylethanolamine molecular subspecies varied according to the time elapsed from the injection to the sacrifice of the animals. This last result, together with the data on time course of labelling of ethanolamine phosphoglycerides and their precursors, provides indications that this base may be incorporated into lipids not only by net synthesis pathway, but also by base-exchange reaction.

Animals↗
PubMed1996

Ethanolamine analogues stimulate DNA synthesis by a mechanism not involving phosphatidylethanolamine synthesis.

Dimethylethanolamine (0.5-1 mM), added to serum-starved NIH 3T3 fibroblasts, stimulated DNA synthesis 11-32-fold, and it also greatly enhanced the relatively modest (15-20-fold) mitogenic effect of insulin. Ethanolamine and monomethylethanolamine alone had no effects on DNA synthesis, but they also enhanced the stimulatory effect of insulin, although less effectively than dimethylethanolamine did. Lower concentrations (2.5-5 microg/ml) of compound D 609 (tricyclo-9-yl-xanthogenate), which had no effects on phospholipase activities, synergistically enhanced the combined effects of ethanolamine analogs and insulin on DNA synthesis without affecting the synthesis of ethanolamine phospholipids. These results suggest that ethanolamine and its analogues, formed by phospholipase D-mediated hydrolysis of ethanolamine phospholipids, may have growth regulatory functions independent of their role as phospholipid precursors.

3T3 Cells↗
PubMed2004

Regulation of the yeast EKI1-encoded ethanolamine kinase by inositol and choline.

Regulation of the EKI1-encoded ethanolamine kinase by inositol and choline was examined in Saccharomyces cerevisiae. Transcription of the EKI1 gene was monitored by following the expression of beta-galactosidase activity driven by a P(EKI1)-lacZ reporter gene. The addition of inositol to the growth medium resulted in a dose-dependent decrease in EKI1 expression. Supplementation of choline to inositol-containing growth medium brought about a further decrease in expression, whereas choline supplementation alone had no effect. Analysis of EKI1 expression in ino2Delta, ino4Delta, and opi1Delta mutants indicated that the transcription factors Ino2p, Ino4p, and Opi1p played a role in this regulation. Moreover, mutational analysis showed that the UAS(INO) element in the EKI1 promoter was required for the inositol-mediated regulation. The regulation of EKI1 expression by inositol and choline was confirmed by corresponding changes in ethanolamine kinase mRNA, protein, and activity levels. The repression of ethanolamine kinase by inositol supplementation correlated with a decrease in the incorporation of ethanolamine into CDP-ethanolamine pathway intermediates and into phosphatidylethanolamine and phosphatidylcholine.

Choline↗
PubMed2005

Acetate excretion during growth of Salmonella enterica on ethanolamine requires phosphotransacetylase (EutD) activity, and acetate recapture requires acetyl-CoA synthetase (Acs) and phosphotransacetylase (Pta) activities.

This report shows that Salmonella enterica catabolizes ethanolamine to acetyl-CoA (Ac-CoA), which enters the glyoxylate bypass and tricarboxylic acid cycle for the generation of energy and central metabolites. During growth on ethanolamine, S. enterica excreted acetate, whose recapture depended on Ac-CoA synthetase (Acs) and the housekeeping phosphotransacetylase (Pta) enzyme activities. The Pta enzyme did not play a role in acetate excretion during growth of S. enterica on ethanolamine. It is proposed that during growth on ethanolamine, acetate excretion is necessary to maintain a pool of free CoA. Acetate excretion requires the eut operon-encoded phosphotransacetylase (EutD) and acetate kinase (Ack) enzymes. EutD function was not required for growth on ethanolamine, and an eutD strain showed only a slight reduction in growth rate. The existence of an as-yet-unidentified system that releases acetate was revealed during growth of a strain lacking Acs, the housekeeping phosphotransacetylase (Pta), and EutD. The functions of pyruvate oxidase (PoxB), Ack and STM3118 protein [a homologue of the Saccharomyces cerevisiae Ac-CoA hydrolase (Ach1p) enzyme] were not involved in the release of acetate by the acs pta eutD strain.

Acetate-CoA Ligase↗
PubMed1988

Ethanolamine utilization in Salmonella typhimurium.

Ethanolamine can serve as the sole source of carbon and nitrogen for Salmonella typhimurium if vitamin B12 is present to serve as a cofactor. The pathway for ethanolamine utilization has been investigated in order to understand its regulation and determine whether the pathway is important to the selective forces that have maintained the ability to synthesize B12 in S. typhimurium. We isolated mutants that are defective in ethanolamine utilization (eut mutants). These mutants defined a cluster of genes located between purC and cysA at 50 min on the Salmonella chromosome. A genetic map of the eut region was constructed. Included in the map are mutations which affect ethanolamine ammonia lyase, the first degradative enzyme, and mutations which affect the second enzyme in the pathway, acetaldehyde dehydrogenase. Transcriptional regulation of the eut genes was studied by using eut-lac operon fusions created by insertion of Mu d lac. Transcription is induced by the simultaneous presence of ethanolamine and B12 in the growth medium. The eut genes constitute a single unit of transcription. One class of mutations located at the promoter-distal end of the eut operon prevent induction of transcription.

Ethanolamines↗
PubMed1994

A rationale for autoinduction of a transcriptional activator: ethanolamine ammonia-lyase (EutBC) and the operon activator (EutR) compete for adenosyl-cobalamin in Salmonella typhimurium.

The ethanolamine utilization (eut) operon of Salmonella typhimurium is controlled by a positive regulatory protein (EutR) which stimulates eut operon expression in response to the simultaneous presence of two effectors, ethanolamine and adenosyl-cobalamin (Ado-B12). Ado-B12 is a cofactor for ethanolamine ammonia-lyase (lyase), the first enzyme in the ethanolamine-degradative pathway. The dependence of this pathway on the use of Ado-B12 as an effector in eut operon induction may be explained by its role in the degradation of ethanolamine and the fact that this cofactor is not always made by S. typhimurium. The eutR gene lies within the eut operon, and its autoinduction is required for maximum operon expression. Evidence is presented that the placement of the eutR regulatory gene within the operon provides a means of balancing the competition between lyase and the regulatory protein for a very small pool of Ado-B12. Since both lyase and the regulatory protein are induced, they can compete more equally for a small pool of Ado-B12. This permits both continued eut operon induction and lyase activity. Two general observations support this model. First, mutations that inactivate lyase allow the operon to be fully induced by a lower level of exogenous cobalamin (CN-B12) than required by a wild-type operon. This increase in sensitivity is measured as a reduction in the apparent Km for operon induction by exogenous CN-B12. Second, the maximum level of operon induction by excess CN-B12 is dictated by the level of EutR regulatory protein, regardless of the level of lyase.

Bacterial Proteins↗
PubMed1987

Preferential synthesis of diacyl and alkenylacyl ethanolamine and choline glycerophospholipids in rabbit platelet membranes.

In rabbit platelet membranes, the contents of alkenylacyl phospholipids (plasmalogen) were 56% of phosphatidylethanolamine and 3% of phosphatidylcholine. This uneven distribution of plasmalogens in each phospholipid class could be attributed to the different substrate specificity of ethanolaminephosphotransferase (EC 2.7.8.1) and cholinephosphotransferase (EC 2.7.8.2). The properties of the enzymes were studied, using endogenous diglycerides and CDP-[3H]ethanolamine or CDP-[14C]choline as substrates. The newly formed phospholipids were mainly diacyl and alkenylacyl and only rarely alkylacyl type. The ratios of the labeled alkenylacyl to diacyl type of phospholipids clearly varied with the concentrations of CDP-ethanolamine or CDP-choline. When 1, 10, and 30 microM CDP-[3H]ethanolamine were used, the labeled phospholipids contained 53, 37, and 27% of the alkenylacyl type, respectively. The apparent Km for CDP-ethanolamine to synthesize alkenylacyl and diacyl types were 2.2 and 8.1 microM. On the other hand, when 1, 10, and 30 microM CDP-[14C]choline were used, the labeled lipids contained 10, 17, and 24% alkenylacyl type, respectively. The apparent Km for CDP-choline to synthesize alkenylacyl and diacyl types were 24 and 4.3 microM. Further, the syntheses of diacyl type of phosphatidylethanolamine and the alkenylacyl type of phosphatidylcholine were markedly inhibited by unlabeled CDP-choline and CDP-ethanolamine, respectively. The two enzymes had opposite substrate specificities, and ethanolaminephosphotransferase showed a high preference to plasmalogen synthesis, especially in the presence of CDP-choline.

Animals↗
PubMed1985

The mechanism of action of ethanolamine ammonia-lyase, an adenosylcobalamin-dependent enzyme. Evidence that the hydrogen transfer mechanism involves a second intermediate hydrogen carrier in addition to the cofactor.

Ethanolamine ammonia-lyase catalyzes the adenosylcobalamin (AdoCbl)-dependent conversion of ethanolamine to acetaldehyde and ammonia. During this reaction, a hydrogen atom migrates from the carbinol carbon of ethanolamine to the methyl carbon of acetaldehyde. Previous studies have shown that this migrating hydrogen equilibrates with the hydrogens on the 5'-(cobalt-linked) carbon of the cofactor. On the basis of those studies, a two-step mechanism for hydrogen transfer has been postulated in which the migrating hydrogen is first transferred from the substrate to the cofactor, then in a subsequent step is returned from the cofactor to the product. We now show that this migrating hydrogen is transferred not only to the cofactor, but also to a second acceptor at the active site. Hydrogens on this acceptor do not exchange with water during the course of the reaction, but are released to water when the enzyme is denatured. The catalytic significance of this second hydrogen acceptor was demonstrated by the findings that the transfer of hydrogen to this acceptor required both AdoCbl and active enzyme and that hydrogen at the second acceptor site could be washed out by unlabeled ethanolamine. On the basis of these results, we propose an expanded hydrogen transfer mechanism in which AdoCbl and the second acceptor site serve as alternative intermediate hydrogen carriers during the course of ethanolamine deamination.

Ammonia-Lyases↗
PubMed1984

The mechanism of action of ethanolamine ammonia-lyase, an adenosylcobalamin-dependent enzyme. Evidence for a carboxyl group at the active site.

Ethanolamine ammonia-lyase is an adenosylcobalamin-dependent enzyme that catalyzes the rearrangement of ethanolamine and other vicinal amino alcohols to oxo-compounds and ammonia. Treatment of this enzyme with the sulfhydryl group-blocking reagent methyl methanethiosulfonate produces a species with diminished catalytic activity. When methyl methanethiosulfonate -treated ethanolamine ammonia-lyase was incubated with a carboxyl-blocking reagent consisting of glycine ethyl ester plus a water-soluble carbodiimide, the enzyme lost more than 80% of its residual activity, while at the same time glycine ethyl ester was incorporated into it at a stoichiometry of 6 mol/mol of enzyme. Both the loss of activity and the incorporation of glycine ethyl ester were prevented if ethanolamine was included in the glycine ethyl ester-containing incubation mixture. These results suggest that an active site carboxyl group plays a role in the mechanism of catalysis by ethanolamine ammonia-lyase, and that this carboxyl group is amidated when the enzyme is incubated with glycine ethyl ester plus carbodiimide.

Ammonia-Lyases↗
PubMed1979

Alkaline phosphatase, phosphoethanolamine, and ethanolamine content in benign prostatic hypertrophy.

The amino acid patterns of benign prostatic hyperplasia specimens show that the contents of phosphoethanolamine and ethanolamine are very variable from one tissue sample to another. An increased phosphoethanolamine content is accompanied by a low ethanolamine content, and vice versa. The concentrations of the two substances correlate well. There exists a possible involvement of alkaline phosphatase in this inverse relationship between phosphoethanolamine and ethanolamine. In specimens with increased phosphoethanolamine and decreased ethanolamine levels alkaline phosphatase activity was low; however in specimens with decreased phosphoethanolamine and increased ethanolamine levels alkaline phosphatase activity was high.

Alkaline Phosphatase↗
PubMed1976

Phosphatidyl-(N-acyl)-ethanolamine. A lipid component of mammalian epidermis.

A lipid present in the granular cells of mammalian epidermis was identified as phosphatidyl-(N-acyl)-ethanolamine. The structure was deduced from the ratio of phosphorus : nitrogen : glycerol : fatty acid esters : total fatty acid (1 : 0.94 : 0.97 : 2.1 : 2.9), from analyses of the products of alkaline and acid hydrolyses and from its infrared spectrum. Conclusive evidence was obtained by a direct comparison of the chromatographic properties, degradation products and infrared spectrum of the isolated lipid with those of synthetic 1,2-dipalmitoyl-sn-glycero-3-phospho-(N-palmitoyl)-ethanolamine. The fatty acids attached to the ethanolamine were predominantly saturated (69% of total) and hexadecanoic acid was the major component (41% of total). Phosphatidyl-(N-acyl)-ethanolamine was hydrolysed by a phospholipase C (Bacillus cereus) to diacylglycerol, inorganic phosphorus and N-acylethanolamine. Evidence for the presence of N-acylethanolamine in granular cells and in stratum corneum suggested that an epidermal phospholipase C may be involved in the catabolism of phosphatidyl-(N-acyl)-ethanolamine.

Animals↗
PubMed1992

Phosphatidylcholine Synthesis in Castor Bean Endosperm : Occurrence of an S-Adenosyl-l-Methionine:Ethanolamine N-Methyltransferase.

Methylethanolamine synthesis by S-adenosyl-l-methionine:ethanolamine N-methyltransferase from an extract of castor bean (Ricinus communis L. var Hale) endosperm was characterized. The apparent Michaelis-Menten constants of the enzyme for ethanolamine and S-adenosyl-l-methionine were estimated to be 6.7 and 1.4 mum, respectively, although the K(m) for ethanolamine is imprecise because of strong substrate inhibition. The pH optimum was 8.0, and a divalent cation was required for activity, with Mg(2+) giving the greatest stimulation at 5 mm. The enzyme was inhibited by calcium in the micromolar range and relatively high concentrations of ethanolamine (above about 7 mum). The activity was found in the 119,000g supernatant fraction and, therefore, appears to be cytoplasmic. The potential roles of S-adenosyl-l-methionine:ethanolamine N-methyltransferase in choline and phosphatidylcholine synthesis are discussed.

Journal Article↗
PubMed1990

Phosphatidylethanolamine synthesis by castor bean endosperm : membrane bilayer distribution of phosphatidylethanolamine synthesized by the ethanolaminephosphotransferase and ethanolamine exchange reactions.

The bilayer distribution of phosphatidylethanolamine (PtdEtn) in the endoplasmic reticulum of castor bean (Ricinus communis L. var Hale) endosperm following synthesis by both the CDP-ethanolamine: 1,2-diacylglycerol ethanolaminephosphotransferase and ethanolamine base exchange reactions have been studied. Two chemical probes, 1-fluoro-2,4-dinitrobenzene (FDNB) and 2,4,6-trinitrobenzenesulfonic acid (TNBS), which covalently bind to the free amino groups, were utilized. The endoplasmic reticulum membranes were impermeable to TNBS at 4 and 25 degrees C, but were permeable to FDNB at both temperatures. FDNB treatment of the PtdEtn from the base exchange reacted with 92% of the PtdEtn, while 80% of the lipid reacted with TNBS. Thus, at least 80% of the PtdEtn synthesized by the base exchange reaction was localized in the outer leaflet of the membrane, with about 12% occurring on the inner leaflet and about 8% being inaccessible. For PtdEtn formed by the CDP-ethanolamine pathway, 85% reacted with FDNB and 70% with TNBS, indicating that at least 70% was produced to the cytoplasmic face of the ER and 15% to the lumen side. The remainder was inaccessible to the probes. The sensitivity to trypsin of the two reactions also was tested. The ethanolamine base exchange enzyme, as well as that for l-serine exchange, retained activity following exposure to trypsin, but the activity of ethanolaminephosphotransferase disappeared after such treatment. This indicates that both base exchange enzymes are exposed to the lumenal side of the ER, while CDP-ethanolamine: 1,2-diacylglycerol ethanolaminephosphotransferase is exposed on the outer or cytoplasmic side. These results are discussed with respect to the final phospholipid distributions and the presumed sources of the water-soluble substrates.

Journal Article↗
PubMed1984

Ethanolamine glycerophospholipid formation by decarboxylation of serine glycerophospholipids in myelinating organ cultures of cerebellum.

Serine decarboxylation as a source of glycerophospholipid ethanolamine is known to occur in mammals. However, early investigators failed to demonstrate the pathway in brain. In the present study serine is shown to be decarboxylated to glycerophospholipid ethanolamine in myelinating organ cultures of rat cerebellum up to 32 days in vitro. The pattern of incorporation of L-[3-14C]serine into culture phospholipids strongly suggests a precursor-product relationship between serine glycerophospholipids (SGP) and ethanolamine glycerophospholipids (EGP), with serine label appearing in the ethanolamine moiety of EGP. The time course of labelling was similar for both acid-stable and acid-labile EGP. In contrast DL-[1-14C]serine failed to label EGP significantly due to the loss of serine carbon C1 on decarboxylation. Through the systematic hydrolysis of phospholipids from cerebellar cultures incubated with L-[3-14C], it was clear that in SGP, acid-stable EGP, and acid-labile EGP greater than to 70% of radiolabel resides in the base moiety of each of these molecular species. It is proposed that serine decarboxylation as a source of EGP ethanolamine may be important in the early stages of brain development.

Animals↗
PubMed1991

A comparison of sclerosing agents. Clinical and histologic effects of intravascular sodium morrhuate, ethanolamine oleate, hypertonic saline (11.7%), and sclerodex in the dorsal rabbit ear vein.

The dorsal marginal rabbit ear vein was injected with 0.25 mL of 2.5, 1, or 0.5% sodium morrhuate, 2.5, 1, or 0.5% ethanolamine oleate, hypertonic saline 11.7%, or Sclerodex. Only the vessel injected with 2.5% sodium morrhuate demonstrated clinical and histologic evidence of endosclerosis with microangiopathic recanalization; 2.5% ethanolamine oleate demonstrated partial clinical sclerosis and luminal recanalization histologically. All other evaluated solutions except 0.5% ethanolamine oleate produced immediate clinical and histologic endothelial damage and thrombosis. However, these latter solutions did not produce sufficient endothelial damage to cause endosclerosis. Extravasated red blood cells occurred in vessels injected with 1 and 2.5% ethanolamine oleate and 1 and 2.5% sodium morrhuate at 1 hour and 2 days, but not in vessels injected with sodium morrhuate 0.5%, ethanolamine oleate 0.5%, Sclerodex, or hypertonic saline 11.7%. Hemosiderin discoloration was not apparent clinically. Cutaneous necrosis was not observed with any of the evaluated solutions.

Animals↗