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PubMed1987

Phosphatidylethanolamine biosynthesis in rat mammary carcinoma cells that require and do not require ethanolamine for proliferation.

Epithelial cells and some of their transformed derivatives require ethanolamine to grow normally in defined culture medium. When these cells are cultured without ethanolamine, the amount of cellular phosphatidylethanolamine is considerably reduced. Using a set of rat mammary carcinoma cell lines whose growth is responsive (64-24 cells) and not responsive (22-1 cells) to ethanolamine, the biochemical mechanism of ethanolamine responsiveness was investigated. The biosynthesis and metabolism of phospholipid, particularly of those involving phosphatidylethanolamine, were thus compared between the two types of cells. The incorporation of [3H]serine into phosphatidylserine and phosphatidylethanolamine in 64-24 cells was 60 and 37%, respectively, of those in 22-1 cells. However, the activity of phosphatidylserine decarboxylase was virtually the same in these cell lines. When these cells were cultured in the presence of [32P]phosphatidylcholine and [32P]phosphatidylethanolamine, the rate of accumulation of 32P-labeled phosphatidylserine from the radioactive phosphatidylethanolamine was considerably reduced in 64-24 cells compared to that in 22-1 cells, although the rate of synthesis of phosphatidylserine and phosphatidylethanolamine from the radioactive phosphatidylcholine was similar between the two cell lines. The rate of labeling phosphatidylcholine from the radioactive phosphatidylethanolamine was also reduced in 64-24 cells, although the difference was not as great as that of phosphatidylserine. Incorporation of 32P into phosphatidylethanolamine was correlated with the concentration of ethanolamine in the culture medium in 64-24 cells, whereas in 22-1 cells the incorporation was not influenced by ethanolamine. Enzyme activities of the CDP-ethanolamine pathway were not significantly different between the two cell lines. The rate of degradation of phosphatidylethanolamine was also similar in these cell lines. These results show that ethanolamine responsiveness of 64-24 cells, and probably other epithelial cells, is due to a limited ability to synthesize phosphatidylserine resulting from a limited base-exchange activity utilizing phosphatidylethanolamine.

Animals↗

PubMed2005

In vitro selection of DNA aptamers binding ethanolamine.

We have identified aptamers (synthetic oligonucleotides) binding to the very small molecule ethanolamine with high affinity down to the low nanomolar range. These aptamers were selected for their ability to bind to ethanolamine immobilised on magnetic beads, from an 96mer library of initially about 1 x 10(16) randomised ssDNA molecules. The dissociation constants of these aptamers range between K(D)=6 and K(D)=19 nmol L(-1). The aim of the development of ethanolamine aptamers is their use for the detection of this substance in clinical and environmental analysis. Ethanolamine is associated with several diseases. Moreover, ethanolamine and its derivatives di- and tri-ethanolamine are used in chemical and cosmetic industries. The use of biosensors with ethanolamine aptamer as new molecular recognition element could be an innovative method for an easy and fast detection of ethanolamine.

Aptamers, Nucleotide↗

PubMed1997

A novel high-molecular mass mammalian ethanolamine kinase.

The present report describes, for the first time, a mammalian kinase highly specific for ethanolamine (Km = 41 microM). Ethanolamine kinase catalyzes the initial step in the CDP-ethanolamine pathway for phosphatidylethanolamine synthesis. Although plant and protozoan kinases are known to exhibit remarkable specificity for ethanolamine, no equivalent mammalian kinase has been characterized previously. The easily shocked (eas) mutant of Drosophila has been characterized and found to lack ethanolamine kinase activity while still possessing normal choline kinase activity (Pavlidis, P., Ramaswami, M., and Tanouye, M.A. (1994) Cell 79, 23-33). The gene compensating this mutation encodes a sequence resembling that of choline kinase. In the present report, the eas gene product, expressed in Escherichia coli as fusion protein, is found to have highly specific ethanolamine kinase activity. Anti-eas antibody revealed a protein with a molecular mass of approximately 86 kDa in rat tissues and human HeLa cells by Western blotting, but did not bind rat choline kinase isozymes. Rat liver kinase activity specific for ethanolamine was separated chromatographically and by an immunological procedure using anti-choline kinase antibody, associated with the 86 kDa protein, and immunoprecipitated by anti-eas antibody. This 86 kDa protein is characterized as ethanolamine kinase. Relations with previously reported kinases are discussed.

Animals↗

PubMed1977

Choline kinase and ethanolamine kinase are separate, soluble enzymes in rat liver.

Choline kinase and ethanolamine kinase are located in the cytosol from rat liver and have been copurified more than 500-fold by affinity chromatography [P. J. Brophy and D. E. Vance (1976) FEBS Lett. 62, 123-125]. Kinetic properties of the two activities were determined. Choline kinase had a Km for choline of 0.033 mM and ethanolamine was a competitive inhibitor (Ki = 6.2 mM). Ethanolamine kinase had a Km for ethanolamine of 7.7 mM and choline was a 'mixed' type of inhibitor with a Ki of 0.037 mM. Both enzymes activities responded in a similar fashion to the adenylate energy charge. Betaine and choline phosphate partially inhibited both kinases with a 93% inhibition of the ethanolamine kinase by 5 mM choline phosphate. CTP and ethanolaminephosphate partially inhibited the ethanolamine kinase, but not the choline kinase. Other metabolites tested had negliglible effects on both kinases. The affinity-column-purified enzyme was analyzed by disc gel electrophoresis which resolved the two activities. Hence, although many of the properties of the two activities are similar, choline kinase and ethanolamine kinase must be separate enzymes. Analysis of rat liver cytosol by disc gel electrophoresis indicated four isoenzymes for choline kinase and ethanolamine kinase.

Adenine Nucleotides↗

PubMed1995

Ethanolamine oleate versus butyl cyanoacrylate for bleeding gastric varices: a nonrandomized study.

BACKGROUND AND STUDY AIMS: Sclerotherapy may be useful in patients with bleeding gastric varices. The aim of this study was to compare the effects of two sclerosants in these patients. PATIENTS AND METHODS: In a prospective nonrandomized trial, we performed single sclerotherapy for bleeding gastric varices using ethanolamine oleate (n = 24) or butyl cyanoacrylate (n = 29). The patients were followed for a mean of 14 months. RESULTS: The rate of initial hemostasis (no bleeding occurred for 48 hours after sclerotherapy) was significantly higher in the butyl cyanoacrylate group (93%) than in the ethanolamine oleate group (67%) (p = 0.014). The rate of initial hemostasis in cardiac variceal bleeding did not differ significantly between the ethanolamine oleate and butyl cyanoacrylate groups (83% vs. 100%, p = 0.140). In contrast, the hemostasis rate for fundal variceal bleeding was significantly higher in the butyl cyanoacrylate group than in the ethanolamine oleate group (88% vs. 50%, p = 0.023). Although the rebleeding rate did not differ between the two groups (30% vs. 25%, p = 0.921), the mortality rate was significantly higher in the ethanolamine oleate group (67% vs. 38%, p = 0.043). In addition, the incidence of complications in the butyl cyanoacrylate group was similar to that in the ethanolamine oleate group (46% vs. 41%, p = 0.745). CONCLUSIONS: These results suggest that initial control of fundal varices is more difficult than it is with cardiac varices, but butyl cyanoacrylate is superior to ethanolamine oleate, and the survival advantage from butyl cyanoacrylate seems to be partially related to the increased early bleeding deaths in the ethanolamine oleate group.

Adult↗

PubMed1993

Levels of ethanolamine intermediates in the human and rat visual system structures: comparison with neural tissues of a lower vertebrate (Mustelus canis) and an invertebrate (Loligo pealei).

Levels of ethanolamine intermediates in the retina and optic nerves of autopsied human donors and in the rat visual system (retina, optic nerve, lateral geniculate body, superior colliculus) were measured. Amounts were also obtained from the retina, optic nerve, and optic tectum of a primitive elasmobranch, the smooth dogfish Mustelus canis, and from the related nervous structures (retina, optic lobe, fin nerve, and stellate ganglia) of a marine invertebrate, the squid Loligo pealei. In all regions of the human and rat nervous system, the pool size of CDP-ethanolamine (values ranging between 10-31 nmol/g wet wt) was much smaller than that of free ethanolamine (values ranging between 197-395 nmol/g wet wt), whereas glycerophosphorylethanolamine was present in relatively high content (values ranging between 125-280 nmol/g wet wt). In nervous system regions of the dogfish and squid, the distribution of values followed the same general trend as observed for humans and rats, even if all regions had less ethanolamine intermediates compared to the mammalian counterpart. In dogfish and squid retina, glycerophosphorylethanolamine showed the highest pool size among the ethanolamine derivatives analyzed (16 and 44 nmol/g wet wt, respectively). The present study confirms the basic similarity of ethanolamine intermediate pool size patterns in the nervous system structures (with the exception of the retina) of animal species which have widely different phylogenetic positions. The data support the proposal that the levels reached by ethanolamine and its derivatives in the nervous tissue is the result of an ancient evolutionary development of metabolic pathways for the maintenance of phosphatidylethanolamine membraneous content.

Adolescent↗

PubMed1985

Distribution and metabolism of topically applied ethanolamine.

The distribution and metabolism of topical [14C]ethanolamine was studied in vivo, using athymic nude mice, human skin grafted onto athymic nude mice, and in vitro, using excised pig skin. Ethanolamine was the only radioactive phospholipid base detected in the human skin grafts, in the mouse skin, and in the pig skin. Ethanolamine that penetrated human skin grafts or mouse skin was extensively metabolized in the animal. The liver is a major site for metabolism of ethanolamine, containing over 24% of the applied radioactive dose. The kidneys, lungs, brain, and the heart contained 2.53, 0.55, 0.27, and 0.15% of the dose, respectively. The hepatic phospholipid bases, ethanolamine, choline, and serine, were all highly radioactive. Hepatic, human skin graft, and mouse skin proteins were also highly radioactive. Over 18% of the topical radioactive dose was oxidized to 14CO2 and 4.6% was excreted in the urine over 24 hr. Urea, glycine, serine, choline, and uric acid were the urinary metabolites of ethanolamine. In vitro data showed that a relatively small percentage of the applied dose was lost from the skin by evaporation and percutaneous penetration. The bulk of the dose remained in the epidermis. Radiometric and enzymatic assays suggest that ethanolamine enhances the hydrolysis of topically applied diisopropylfluorophosphate.

Administration, Topical↗

PubMed1989

Biosynthesis of phosphatidylethanolamine via the CDP-ethanolamine route is an important pathway in isolated rat hepatocytes.

In the present study pulse-label and pulse-chase experiments with isolated rat hepatocytes in suspension were designed to investigate the effects of the presence of either serine or ethanolamine in the medium on the rate of phosphatidylethanolamine synthesis via the CDPethanolamine pathway and by decarboxylation of phosphatidylserine. Addition of serine to the medium did not affect the incorporation of [1,2-14C]ethanolamine into phosphatidylethanolamine. Pulse-label experiments showed that the incorporation of [3H]serine into phosphatidylserine decreased in the presence of ethanolamine with a corresponding decrease of the incorporation of label into the ethanolamine base moiety of phosphatidylethanolamine. However, the radioactivity in the diacylglycerol part of phosphatidylethanolamine was considerably higher in the presence of ethanolamine than in its absence. Pulse-chase experiments with labelled serine demonstrated that the conversion of phosphatidylserine to phosphatidylethanolamine was not affected by varying concentrations of ethanolamine. Our observations indicate that in the presence of ethanolamine the biosynthesis of phosphatidylethanolamine via the CDPethanolamine pathway is enhanced relative to the synthesis by decarboxylation of phosphatidylserine.

Animals↗

PubMed1989

Conversion of ethanolamine, monomethylethanolamine and dimethylethanolamine to choline-containing compounds by neurons in culture and by the rat brain.

The incubation of neurons from chick embryos in primary culture with [3H]ethanolamine revealed the conversion of this base into monomethyl, dimethyl and choline derivatives, including the corresponding free bases. Labelling with [methyl-3H]monomethylethanolamine and [methyl-3H]dimethylethanolamine supported the conclusion that in chick neuron cultures, phosphoethanolamine appears to be the preferential substrate for methylation, rather than ethanolamine or phosphatidylethanolamine. The methylation of the latter two compounds, in particular that of phosphatidylethanolamine, was seemingly stopped at the level of their monomethyl derivatives. Fetal rat neurons in primary culture incubated with [3H]ethanolamine showed similar results to those observed with chick neurones. However, phosphoethanolamine and phosphatidylethanolamine and, to a lesser extent, free ethanolamine, appeared to be possible substrates for methylation reactions. The methylation of water-soluble ethanolamine compounds de novo was further confirmed by experiments performed in vivo by intraventricular injection of [3H]ethanolamine. Phosphocholine and the monomethyl and dimethyl derivatives of ethanolamine were detected in the brain 15 min after injection.

Animals↗

PubMed1988

Carcinoembryonic antigen is anchored to membranes by covalent attachment to a glycosylphosphatidylinositol moiety: identification of the ethanolamine linkage site.

The COOH-terminal amino acid of carcinoembryonic antigen (CEA) is shown to covalently link with ethanolamine, evidence consistent with the anchorage of CEA to the plasma membrane through a phosphatidylinositol-glycan tail. Purified CEA was digested with trypsin, and the resulting peptides were isolated by reverse-phase HPLC. Tryptic hexapeptide T12, terminating atypically with alanine, corresponded in sequence (Ser-Ile-Thr-Val-Ser-Ala) with the last six residues (637-642) of the third repeating domain in the mature CEA protein. Mass determination of the hexapeptide by fast atom bombardment mass spectrometry suggested the presence of an additional ethanolamine moiety. This finding and the absence of the subsequent 26 hydrophobic residues predicted by cDNA sequence is evidence that hexapeptide T12 is the COOH-terminal peptide of mature CEA. A synthetic peptide identical to hexapeptide T12 was prepared, and ethanolamine was coupled to its COOH-terminal alanine; chromatographic properties of this synthetic ethanolamine-coupled peptide and peptide T12 were the same. B/E-linked-scan mass spectral analysis of the ethanolamine-coupled synthetic peptide and peptide T12 revealed a fragment ion series consistent with the presence of a COOH-terminal ethanolamine. Release of membrane-bound CEA from the CEA-expressing cell line LS 174T was shown by indirect immunofluorescence and flow cytometry after treatment with phosphatidylinositol-specific phospholipase C. We conclude that CEA is processed posttranslationally to remove the hydrophobic COOH-terminal residues (643-668) with subsequent addition of an ethanolamine-glycosylphosphatidylinositol moiety and that treatment of a colonic cell line with phosphatidylinositol-specific phospholipase C releases membrane-bound CEA.

Adenocarcinoma↗

PubMed1977

Microbial metabolism of amino alcohols. Control of formation and stability of partially purified ethanolamine ammonia-lyase in Escherichia coli.

Induction of ethanolamine ammonia-lyase formation in Escherichia coli required both the ethanolamine and vitamin B12, and was gratuitous during growth on glycerol. Ethanolamine analogues inhibited enzyme activity and inhibited growth with ethanolamine as the the nitrogen source, but did not act as inducers. Enzyme formation was more rapid when ethanolamine was added to cultures containing vitamin B12 rather than the reverse. Enzyme formation was subject to catabolic repression, glucose and acetate being particularly effective. Chloramphenicol, I-aminopropan 2-01 and 1,3-diaminopropan-2-01 prevented enzyme induction. Ethanolamine ammonia-lyase, resolved from its cobamide coenzyme, was purified 35-fold. The apoenzyme was stable for several days in the presence of ethanolamine, dithiothreitol, glycerol and K+ ions. Enzyme formation therefore requires both substrate and cobamide coenzyme to be present simultaneously as inducers.

Amino Alcohols↗

PubMed1995

Ethanolamine utilization in Salmonella typhimurium: nucleotide sequence, protein expression, and mutational analysis of the cchA cchB eutE eutJ eutG eutH gene cluster.

A fragment of the Salmonella typhimurium ethanolamine utilization operon was cloned and characterized. The 6.3-kb nucleotide sequence encoded six complete open reading frames, termed cchA, cchB, eutE, eutJ, eutG, and eutH. In addition, the nucleotide sequences of two incomplete open reading frames, termed eutX and eutI, were also determined. Comparison of the deduced amino acid sequences and entries in the GenBank database indicated that eutI encodes a phosphate acetyltransferase-like enzyme. The deduced amino acid sequences of the EutE and EutG proteins revealed a significant degree of homology with the Escherichia coli alcohol dehydrogenase AdhE sequence. Mutations in eutE or eutG completely abolished the ability of mutants to utilize ethanolamine as a carbon source and reduced the ability to utilize ethanolamine as a nitrogen source. The product of eutE is most probably an acetaldehyde dehydrogenase catalyzing the conversion of acetaldehyde into acetyl coenzyme A. The product of the eutG gene, an uncommon iron-containing alcohol dehydrogenase, may protect the cell from unconverted acetaldehyde by converting it into an alcohol. The deduced amino acid sequence of cchA resembles that of carboxysome shell proteins from Thiobacillus neapolitanus and Synechococcus sp. as well as that of the PduA product from S. typhimurium. CchA and CchB proteins may be involved in the formation of an intracellular microcompartment responsible for the metabolism of ethanolamine. The hydrophobic protein encoded by the eutH gene possesses some characteristics of bacterial permeases and might therefore be involved in the transport of ethanolamine. Ethanolamine-utilization mutants were slightly attenuated in a mouse model of S. typhimurium infection, indicating that ethanolamine may be an important source of nitrogen and carbon for S. typhimurium in vivo.

Alcohol Dehydrogenase↗

PubMed1989

Biosynthetic incorporation of [3H]ethanolamine into protein synthesis elongation factor 1 alpha reveals a new post-translational protein modification.

Biosynthetic incorporation of [3H]ethanolamine into proteins was assessed in the human erythroleukemia cell line K562. A single predominant labeled protein of about 50 kDa was observed following electrophoresis of cell extracts on polyacrylamide gels in the presence of sodium dodecyl sulfate. Subcellular fractionation showed this protein to distribute similarly to a 46-kDa [3H]ethanolamine-labeled protein reported previously (Tisdale, E. J., and Tartakoff, A. M. (1988) J. Biol. Chem. 263, 8244-8252). In particular, the protein was enriched in cytosolic and microsomal fractions relative to plasma membrane and thus did not appear to correspond to the class of proteins with glycoinositol phospholipid anchors, the only post-translational protein modification involving ethanolamine that had been described previously. Two-dimensional polyacrylamide gel analysis involving isoelectric focusing followed by electrophoresis in sodium dodecyl sulfate indicated that the protein was very basic, and nitrocellulose blots of one- and two-dimensional gels subjected to 3H autoradiography and immunostaining with antisera to purified rabbit elongation factor (EF) 1 alpha revealed that the protein was EF-1 alpha. Copurification of rabbit EF-1 alpha and the [3H]ethanolamine-labeled protein from K562 cells further supported this identification. Analysis of tryptic fragments produced from the copurified proteins by reverse-phase high pressure liquid chromatography showed two radiolabeled peptides. Amino acid analysis demonstrated 1 residue of ethanolamine in each peptide, and peptide sequencing revealed that the ethanolamine-containing component(s) was attached to Glu301 and Glu374 in the EF-1 alpha protein sequence deduced from a human EF-1 alpha cDNA. These data confirm a new class of post-translational protein modifications involving ethanolamine.

Animals↗

PubMed1988

Extensive labeling with [3H]ethanolamine of a hydrophilic protein of animal cells.

Murine T-lymphomas and Thy-1- mutants were labeled overnight with [3H]ethanolamine to detect proteins which possess a glycophospholipid anchor. When labeled cells were treated with 10% trichloroacetic acid and then analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography, both Thy-1 and a second intensely labeled protein (46 kDa) were observed. The presence of the radiolabeled 46-kDa protein in wild type and class E Thy-1 negative cells (cells in which Thy-1 is synthesized but cannot be labeled with [3H]ethanolamine) suggested incorporation into a distinct moiety. Labeling of the 46-kDa protein with [3H]ethanolamine is rapidly inhibited by cycloheximide. Further characterization of the 46-kDa protein by subcellular fractionation and Triton X-114 partitioning indicated that the protein is located in the cytosol. The protein is basic and does not bind to either concanavalin A or wheat germ agglutinin. Labeling of a 46-kDa protein has also been demonstrated in Chinese hamster ovary, COS, rat myeloma, cloned human T-lymphocytes, and HeLa cells. Pronase digestion of the [3H]ethanolamine-labeled 46-kDa protein of wild type lymphoma cells generated a nonbasic and polar labeled fragment which is labile to strong acid and base ([3H]ethanolamine is liberated), insensitive to periodate oxidation and alkaline phosphatase, and does not bind to concanavalin A or wheat germ agglutinin. Judging from methylation studies, the labeled ethanolamine residue does not contain a free amino group. Based on these results, we report a novel post-translational modification of selected protein(s) by the covalent addition of [3H]ethanolamine.

Amino Acids↗

PubMed1983

Significance of yeast peroxisomes in the metabolism of choline and ethanolamine.

The yeasts Candida utilis and Hansenula polymorpha were able to grow in media containing choline or ethanolamine as the sole nitrogen source. During growth in the presence of these substrates, large peroxisomes developed in the cells, and extracts of choline-grown C. utilis cells contained increased levels of amine oxidase and catalase. Incubation of whole cells with choline in the presence of the amine oxidase inhibitor aminoacetonitrile led to excretion of dimethylamine and methylamine. Cytochemical experiments in which spheroplasts prepared from choline-grown cells were incubated with CeCl3 and choline, trimethylamine, dimethylamine or methylamine revealed positively stained peroxisomes, whereas in the presence of 1 mM aminoacetonitrile staining was not observed. This indicated that choline was degraded via methylated amines and that peroxisomes played a role in its metabolism. A similar involvement of peroxisomes in choline degradation was observed in H. polymorpha. Cell-free extracts of ethanolamine-grown C. utilis and H. polymorpha also contained increased levels of amine oxidase and catalase. Ethanolamine was oxidized by cell-free extracts of both organisms after growth in the presence of ethanolamine or choline. Incubation of spheroplasts of ethanolamine- or choline-grown C. utilis with CeCl3 and ethanolamine resulted in positively stained peroxisomes. In this organism peroxisomes were therefore also involved in ethanolamine degradation.

Ascomycota↗

PubMed1992

Ethanolamine is released from glial cells in primary culture on stimulation with foetal calf serum and phorbol ester.

Ethanolamine is released to the external medium at increased rates over basal levels when [3H]ethanolamine-labelled glial cells in primary culture, subcultures of astrocytes and O-2A lineage glia or C6 glioma cells are treated with phorbol ester or foetal calf serum. On equilibrium labelling of mixed glial cultures 90-95% of incorporated [3H]ethanolamine was in ethanolamine-containing phospholipids and 2% in the phosphatidylcholine component. On stimulation of glia with phorbol ester or foetal calf serum ethanolamine, and not phosphoethanolamine or choline, was released to the medium suggesting that a phospholipase D-mediated turnover of lipid, perhaps partially linked to protein kinase C, is involved. The results show that cells in primary culture behave similarly to cell lines in that signal transduction pathways involve a stimulated turnover of ethanolamine-phospholipids with the external release of ethanolamine.

Animals↗

PubMed1978

Evidence for the existence of a single enzyme catalyzing the phosphorylation of choline and ethanolamine in primate lung.

Choline kinase (ATP:choline phosphotransferase, EC 2.7.1.32) has been isolated and purified 1000-fold from adult African Green monkey lung with a yield of 10%. The purified enzyme also phosphorylated ethanolamine (ratio of ethanolamine kinase to choline kinase = 0.30). This ratio remained constant throughout the purification procedure. The Km for choline (3.0 - 10(-5) M) was lower than that of ethanolamine (1.2 - 10(-3) M.) Choline was also found to inhibit ethanolamine kinase activity by 50% at a concentration of 0.005 mM, while ethanolamine inhibited choline only at very high concentrations (100--150 mM). When the enzyme was subjected to inactivation by heat, hemicholinium-3, trypsin digestion, and p-hydroxymercuribenzoate, both ethanolamine kinase and choline kinase activities were destroyed at the same rate. Freezing and thawing in the absence of glycerol also destroyed both activities at the same rate. Based on these findings, we conclude that in adult African Green monkey lung tissue, there is only one enzyme for the phosphorylation of ethanolamine and choline, and that choline phosphorylation predominates.

Animals↗

PubMed1967

Phosphorylation of choline and ethanolamine in Ehrlich ascites-carcinoma cells.

1. Ehrlich ascites-cell extracts convert choline and ethanolamine approximately equally well into their respective phosphoryl derivatives. 2. Choline is a potent inhibitor of ethanolamine phosphorylation, but ethanolamine has little effect on choline phosphorylation. 3. 2,3-Dimercaptopropanol, cysteine and Ca(2+) inhibit ethanolamine phosphorylation, but have no detectable effect on choline phosphorylation. 4. Choline-phosphorylating activity in Ehrlich ascites-cell extracts is more stable during storage than ethanolamine-phosphorylating activity. 5. Choline phosphorylation is stimulated in the presence of benzoylcholine, succinylcholine, butyrylcholine and propionylcholine, whereas ethanolamine phosphorylation is inhibited. This relationship is reciprocal: the compounds causing the greatest stimulation of choline phosphorylation bring about the greatest inhibition of ethanolamine phosphorylation.

Adenosine Triphosphate↗