Choline phosphotransferase

Miquel, K., Pradines, A., Terce, F., Sehni, S., and Favre, G., 1998, Compehhve inhibition of choline phosphotransferase by geranylgeraniol and famesol inhibits phosphatidylchohne synthesis and induces apoptosis in human lung adenocarcinoma A549 ceUs. JBiol Chem. 273 26179-26186... 

ALKENYLGLYCEROPHOSPHOETHANOL-AMINE HYDROLASE 1-ALKYL-2-ACETYLGLYCEROL CHOLINE PHOSPHOTRANSFERASE 1-ALKYL-2-ACETYLG LYCEROPHOSPHO-CHOLINE ESTERASE Alkylation,... 

Adversely affects phospholipid composition and synthesis in roots and microsomes from seedlings by inhibition of choline phosphotransferase (6)... 

Belver, A. and J.P. Donaire. 1987. Phospholipid metabolism in roots and microsomes of sunflower seedlings inhibition of choline phosphotransferase activity by boron. Phytochem. 26 2923-2921. 

These studies demonstrate that choline ingested in the form of lecithin or lecithin precursors [diacylglycerol choline phosphotransferase (CDP)-choline] can improve mild memory loss associated with the aging process. Choline chloride, however, appears to be less effective than lecithin for improving memory, likely because of its lower bioavailability (300). 

The type II pneumocytes synthesize phosphatidylcholine in a fashion quite different from that in other cells. Most other cells synthesize phosphatidylserine from cytidine diphosphate diacylglycerol and serine. The phosphatidylserine is then decarboxylated to yield phosphatidyl ethanoiamine. The final step is the successive donation of three methyl groups via S-adenosylmethionine to form phosphatidylcholine. The pulmonary biosynthetic pathway is shown in Figure 54-2. The enzyme choline phosphotransferase forms PC directly from cytidine diphosphocholine and diacylglycerol. Phosphatidylinositol formation peaks at about 35 weeks. As PI decreases in concentration, PG begins to increase. 

The uptake of exogenous choline for PC synthesis is accepted (31,32), although the nature of transport is contentious (33,34). The disparate observations are perhaps due to variance in experimental technique age of the erythrocytes employed cation imbalance reaction termination conditions in vitro choline concentration and innate characteristics of the two Plasmodium species examined (33,34). It is also possible that interspecies differences in the enzymes involved in the ensuing metabolic fate of choline, for example choline kinase (35) or choline phosphotransferase (36), also influence the results, as well as interactions between the alternative pathways of PC synthesis from PE and PS. In a study of regulation of PC biosynthesis in P. knowlesi-infected erythrocytes (37), the parasite showed a comprehensive ability to modulate the pathway of PC synthesis from external choline depending on the availability of precursors, or alternative pathways. 

DAG produced via the action of PA phosphatase can also be converted to PC by the catalytic action of choline phosphotransferase (CPT). Production of polyunsaturated FAs via the catalytic action of membrane-bound desaturases occurs while monounsaturated FAs are esterifled to the glycerol backbone of PC. The combined forward and reverse reactions catalyzed by lysophosphatidylcholine acyltransferase (LPCAT) are believed to facilitate acyl exchange at the sn-2 position of PC, with the acyl-CoA pool thereby allowing incorporation of polyunsaturated FA into TAG via the acyl-CoA-dependent acyltransferase reactions in the mainstream of TAG biosynthesis. The reverse reaction of CPT to produce DAG provides a second opportunity to introduce polyunsaturated FA into TAG. In addition, phospholipase A2 may catalyze the release of free FA from PC. The liberated FA could be reesterified as acyl-CoA for use in the mainstream of TAG biosynthesis. 

McMaster, CR Bell, RM. CDP-choline 1,2-diacylglycerol choline phosphotransferase. 

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... 

Choline, 277,280 Choline kinase, 504 Choline phosphotransferase, 504,512 Chordata, wax esters, 147 Chromatography, 179,273-77,279,281-83 Chromic acid, 274 Chrysanthemum coronarium, 52 Chrysobalanus icaco, 11 Churning in butter production, 224 Chylomicrons, 382,534-39 Cigarette smoking and cardiovascular disease, 534 Cinnamon oil, 51 Circular dichroism, 300 Citric acid and esters, 228,232,453 Claviceps, 151,492... 

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...

When applied to barley aleurone layers, gibberellic acid stimulated the incorporation of [met/iy/- CJcholine into PC (Evins and Varner, 1971). Absci-sic acid prevented this effect of gibberellic acid. Johnson and Kende (1971) showed that gibberellin stimulated both PC cytidyltransferase and choline phosphotransferase and that these stimulations could be prevented by absci-sic acid, cycloheximide, and actinomycin D. 

If these drugs reach the endoplasmic reticulum an altered formation of the diacylglycerol pool specific for the choline-phosphotransferase may explain the inhibition observed. The shift in the biosynthetic flow towards IPG may be due to a rapid inhibition of phos-phatidate phosphatase as a result of this CPG and EPG as well as... 

PC is synthesized in plant cells via the CDP-choline pathway, which includes three enzymatic steps catalyzed by choline kinase (EC 2.7.1.32 CKI), CTPiphosphocholine cytidylyltransferase (EC 2.7.7.15 CCT) and CDP-choline diacylglycerol choline-phosphotransferase (EC 2.7.8.2 CPT). Among them, CCT has been reported to be a rate-limiting enzyme [3]. 

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