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PubMed1987

Comparison of cytidinediphospho-sn-1,2-diglyceride transfer from microsomal and liposomal to mitochondrial membranes.

Transfer of [3H]CDP-diglycerides from isolated guinea pig liver microsomal and liposomal membranes to guinea pig mitochondrial membranes was studied by incubating microsomal or liposomal membranes carrying [3H]CDP-diglycerides with mitochondrial membranes and determining the CDP-diglyceride-dependent incorporation of sn-3-[14C]glycerolphosphate into mitochondrial [14C]polyglycerophosphatides. A significant difference in the amount of transferred [3H]CDP-diglycerides and the composition of mitochondrial [14C]polyglycerophosphatides was found depending on whether [3H]CDP-diglycerides were transferred from microsomal or liposomal membranes. This amount was around 12% when [3H]CDP-diglycerides were transferred from the microsomal membranes and around 4.6% when they were transferred from the liposomal membranes. Furthermore, about 60% of [14C]phosphatidylglycerol and 35% of [14C]phosphatidylglycerophosphate were found in the microsomes-mitochondria system and about 9% of [14C]phosphatidylglycerol and 79% of [14C]phosphatidylglycerophosphate were found in the liposomes-mitochondria system, establishing an important role for the membrane donor in the transfer of [3H]CDP-diglycerides to mitochondria. Furthermore, if the transfer of [3H]CDP-diglycerides from the microsomal to the mitochondrial membranes was assayed by the determination of [3H]CDP-diglycerides in reisolated mitochondrial membranes without further incorporation into mitochondrial polyglycerophosphates, it amounted to about 38%.

Animals↗
PubMed1979

Production of diglyceride from phosphatidylinositol in activated human platelets.

Human platelets generate diglyceride within 5 s of exposure to thrombin. Production of diglyceride is transient. 15 s after the addition of thrombin, the levels of diglyceride have increased up to 30-fold, but decrease thereafter. Prior incubation of platelets with 2 mM dibutyryl cyclic AMP prevents both the generation of diglyceride and the secretion of serotonin. Acetylsalicylic acid (100 microgram/ml), which completely inhibits prostaglandin endoperoxide synthesis, does not block diglyceride production and serotonin secretion induced by thrombin. Based on studies examining the incorporation of [3H]arachidonic acid into diglyceride of prelabeled platelets exposed to thrombin, it is concluded that neither phosphatidic acid nor triglyceride is the source of the diglyceride. Phosphatidylinositol appears to be the most likely source, both because its loss of radiolabel is sizable and rapid enough to account for the appearance of radiolabel in diglyceride, and because a phosphatidylinositol-specific phosphodiesterase, described in this report, exists in platelets. The phosphatidylinositol-phosphodiesterase, which produces diglyceride and inositol phosphate, requires Ca+2 and shows optimal activity at pH 7. The enzyme does not act upon phosphatidylcholine, phosphatidylethanolamine, or phosphatidylserine.

Arachidonic Acids↗
PubMedDate not supplied

Localization of the tri- and digalactosyl diglyceride in the thylakoid membrane with serological methods.

Trigalactosyl diglyceride was isolated from leaves of Urtica dioica and characterized by thin layer chromatography, infrared spectroscopy and by its fatty acid composition. An antiserum to the trigalactolipid was obtained by immunization of rabbits. By means of inhibition experiments with oligosaccharides and mono- and digalactosyl glycerol it was demonstrated that the antibodies are directed towards the alpha-galactosyl-(1 leads to 6)-alpha-galactosyl-(1 leads to 6)-beta-galactosyl-(1 leads to 1)-glycerol configuration of the trigalactosyl diglyceride. Monogalactosyl diglyceride and sulfoquinovosyl diglyceride do not react with this antiserum. However, a cross reaction was observed with digalactosyl diglyceride. The presence of antibodies to tri- and digalactosyl diglyceride was demonstrated in antisera to different chloroplast preparations of Antirrhinum majus and Spinacia oleracea. The antiserum to the trigalactolipid agglutinates stroma-freed chloroplasts. Membrane fragments obtained by the ultra sonication were precipitated. The antiserum is exhausted by trigalactosyl diglyceride but not by digalactosyl diglyceride or digalactosyl glycerol. The antiserum treated with digalactosyl glycerol and digalactosyl diglyceride also agglutinated stroma-freed chloroplasts. 1 g stroma-freed chloroplasts binds 0.17 g antibodies to trigalactolipid. Membrane fragments bind more antibodies to trigalactolipids than stroma-freed chloroplasts. From the agglutination tests it follows that the antigenic determinants of the trigalactolipid and the digalactolipid are localized in the outer surface as well as in the surface directed towards the inside of the thylakoid membrane.

Animals↗
PubMed1990

Differential metabolism of diradyl glycerol molecular subclasses and molecular species by rabbit brain diglyceride kinase.

Elevations in the mass of ether-linked diglycerides (i.e. 1-O-alk-1'-enyl-2-acyl-sn-glycerol (AAG) and 1-O-alkyl-2-acyl-sn-glycerol (Alkyl AG)) during cellular activation are prolonged in comparison to their 1,2-diacyl-sn-glycerol (DAG) counterparts. Since the metabolic removal of DAG is determined, in large part, by the rate of its phosphorylation by diglyceride kinase, we quantified differences in the activity of diglyceride kinase utilizing individual subclasses of diradyl glycerols as substrate. Rabbit brain microsomal diglyceride kinase activity was over 30-fold greater utilizing DAG as substrate (25.8 nmol.mg-1.min-1) in comparison to AAG (0.8 nmol.mg-1.min-1). No alterations in the affinity of microsomal diglyceride kinase for ATP were present (Km approximately 0.5 mM) utilizing each diradyl glycerol subclass. Similar subclass specificities for diglyceride kinase (i.e. DAG greater than Alkyl AG much greater than AAG) were present in brain and liver cytosol as well as in liver microsomes utilizing multiple assay conditions. In sharp contrast, Escherichia coli diglyceride kinase phosphorylated DAG, Alkyl AG, or AAG diradyl glycerol molecular subclasses at identical rates. Furthermore, although DAG was rapidly hydrolyzed by diglyceride lipase, catabolism of AAG or Alkyl AG by plasmalogenase, alkyl ether hydrolase, or diglyceride/monoglyceride lipase was undetectable. Collectively, these results demonstrate the importance of the differential catabolism of each diradyl glycerol molecular subclass as a primary determinant of their biologic half-lives. Since individual subclasses of diglycerides have distinct physical properties and physiologic functions, these results underscore the importance of lipid subclass specific metabolism in tailoring individual cellular responses during activation.

Animals↗
PubMed1990

Molecular species analysis of mitogen-stimulated 1,2-diglycerides in fibroblasts. Comparison of alpha-thrombin, epidermal growth factor, and platelet-derived growth factor.

Recent studies have implicated the hydrolysis of phosphoinositides and phosphatidylcholine in agonist-stimulated events. The potent mitogen, alpha-thrombin, stimulates the generation of diglycerides in a biphasic and sustained manner in IIC9 fibroblasts (Wright, T. M., Rangan, L. A., Shin, H. S., and Raben, D. M. (1988) J. Biol. Chem. 263, 9374-9380). Using measurements of radiolabeled headgroup release and molecular species analysis, we previously determined that alpha-thrombin generates diglycerides through the hydrolysis of both the phosphoinositides and phosphatidylcholine at early times (15 s), and at later times (greater than or equal to 5 min) through the hydrolysis of primarily, if not exclusively, phosphatidylcholine (Pessin, M. S., and Raben, D. M. (1989) J. Biol. Chem. 264, 8729-8738). In contrast, IIC9 fibroblasts respond to the mitogenic treatments of (a) alpha-thrombin following chymotrypsin pretreatment or (b) epidermal growth factor by increasing their levels of diglycerides in a monophasic and sustained manner (Wright, T. M., Rangan, L. A., Shin, H. S., and Raben, D. M. (1988) J. Biol. Chem. 263, 9374-9380). In this report, we have analyzed the molecular species of the diglycerides generated by these two different treatments and have also examined the lipid response of IIC9 fibroblasts to platelet-derived growth factor. Based on both the molecular species analyses and the release of radiolabeled head-groups, all three of these different mitogenic treatments generate diglycerides primarily through the stimulation of phosphatidylcholine hydrolysis. However, while similar, the molecular species profiles of the diglycerides generated by these three treatments are not identical to the molecular species profile of total cellular phosphatidylcholine. In addition, the molecular species profiles of the diglycerides generated by these three mitogenic treatments greatly resemble each other, with significant differences between any two profiles occurring in at most one molecular species. This finding differs from that seen with alpha-thrombin stimulation alone, where the molecular species profile of the diglycerides generated following 5 min of alpha-thrombin stimulation is nearly identical to the molecular species profile of total cellular phosphatidylcholine. These data support the possibility of hormone-sensitive phosphatidylcholine pools or selective diglyceride metabolism.

Animals↗
PubMed1988

Structural studies on the diglyceride-mediated activation of protein kinase C.

Diglyceride analogs were studied with respect to their abilities to activate protein kinase C (Ca2+- and phospholipid-dependent protein kinase) in the presence of low calcium and phospholipid. Analogs which lacked either a free hydroxyl group at the 3 position or an ester moiety at the 1 position were without activity. It was concluded that the hydrophilic moieties of the active diglycerides are crucial for activity. However, diglyceride analogs containing additional hydrophilic moieties in one of the acyl side chains did not exhibit enhanced activity when compared to diglycerides containing two fatty acyl groups. Diglyceride analogs with a modified glycerol backbone were also studied. Homologous diglycerides with either one or two methylene groups between the 3-methylene group of the diglyceride and the hydroxyl group possessed markedly reduced activities when compared to the appropriate unmodified diglyceride. Isomers of these homologues which contained either a methyl group at the 1 position, or dimethyl groups incorporated at the 1 and 3 positions, were virtually without activity. Where studied, none of the diglyceride analogs prepared possessed antagonist activity. The results of these experiments are discussed with respect to the extreme specificity observed.

Calcium↗
PubMed1969

Biosynthesis of glucosyl diglycerides by Mycoplasma laidlawii strain B.

Monoglucosyl diglyceride is synthesized from 1,2-diglyceride and uridine-5'-diphosphoglucose (UDP); diglucosyl diglyceride from monoglucosyl diglyceride, and uridine-5'-diphosphoglucose by membranes of Mycoplasma laidlawii strain B. All of these enzymatic activities reside in the membrane. Membranes solubilized by detergent action or succinylation and acetone powders of membranes were inactive. Requirements for Mg(2+), UDP, and appropriate lipid acceptor were demonstrated for biosynthesis of both glycolipids. Glucose-1-phosphate plus uridine triphosphate could replace the UDP requirement. A medium of relatively high ionic strength and a critical concentration of sodium lauryl sulfate stimulated biosynthesis of the monoglucosyl diglyceride. The optimal pH for both reactions was 8.0. A specificity for 1,2-diglyceride from the homologous organism was found for optimal synthesis of the monoglucosyl diglyceride, and a specificity for monoglucosyl diglyceride was found in the case of diglucosyl diglyceride synthesis. Both reactions were specific for UDP.

Buffers↗
PubMed1975

Isolation and characterization of cytidine diphosphate diglyceride from beef liver.

Cytidine diphosphate diglyceride was isolated from beef liver by a combination of silicic acid column, DEAE-cellulose column, and this layer chromatography. The product (5.8 to 17.4 mumol/kg of liver) contained cytidine/phosphate/fatty acids in the molar proportions 1.05/2.0/2.05 (theoretical, 1.0/2.0/2.0) (average for three preparations). The liponucleotide was split quantitatively by a partially purified hydrolase from Escherichia coli, specific for CDP-diglyceride, (Raetz, C. R. H., Hirschberg, C. B., Dowhan, W., Wickner, W. T., and Kennedy, E. P. (1972) J. Biol. Chem. 247, 2245-2247) into phosphatidic acid and a water-soluble nucleotide that was chromatographically identical with CMP. No dCMP was located in these hydrolysates. The liver liponucleotide was more effective than a synthetic preparation of CDP-diglyceride in promoting the formation of phosphatidylinositol with guinea pig brain microsomes. The fatty acid composition of CDP-diglyceride was compared with metabolically related phospholipids from beef liver. The liponucleotide had a similar composition to phosphatidylinositol, characterized by a high level of stearate and with arachidonate as the major unsaturated fatty acid. The content of arachidonate in both lipids was significantly higher than that in phosphatidic acid. The profile of fatty acids of cardiolipin was quite unlike that of CDP-diglyceride. These findings suggest several alternatives for the metabolic origins of beef liver CDP-diglyceride: (a) CDP-diglyceride is formed from an atypical pool of phosphatidic acid, (b) the enzyme is selective for arachidonoyl-containing species of phosphatidic acid, (c) the liponucleotide may also be derived from phosphatidylinositol by the back-reaction of CDP-diglyceride: inositol phosphatidyltransferase.

Animals↗
PubMed1989

Molecular species analysis of 1,2-diglycerides stimulated by alpha-thrombin in cultured fibroblasts.

Diglycerides derived from the phospholipase C-mediated hydrolysis of phosphoinositides are implicated as important mediators of agonist-induced responses, including the stimulation of cell division. alpha-Thrombin-stimulated proliferation of fibroblasts is associated with a sustained increase in cellular diglycerides, while the hydrolysis of phosphoinositides is transient (Wright, T. M., Rangan, L. A., Shin, H. S., and Raben, D. M. (1988) J. Biol. Chem. 263, 9374-9380). A rigorous assessment of this apparent discrepancy requires an analysis of the molecular species of the lipids involved. In this report, we have analyzed the molecular species of 1,2-diglycerides present in quiescent and alpha-thrombin-stimulated IIC9 Chinese hamster embryo fibroblasts. The molecular species profiles of the stimulated diglycerides were compared to the profiles of molecular species contained in cellular phospholipids. We demonstrate that 1) stimulation of IIC9 cells by alpha-thrombin results in an increase in the levels of diglyceride molecular species already present in control, quiescent cultures, without the addition of new species or the complete loss of existing species; 2) the diglycerides present in control cultures as well as in cultures stimulated with alpha-thrombin are all ester-linked; and 3) while the phosphoinositides contribute a significant proportion of the diglycerides generated 15 s following alpha-thrombin addition, phosphatidylcholine contributes most of the diglycerides generated after 5 min and 1 h.

Animals↗
PubMed1983

Chloroform-soluble nucleotides in Escherichia coli. Role of CDP-diglyceride in the enzymatic cytidylylation of phosphomonoester acceptors.

CDP-diglyceride, the precursor of all the phospholipids in Escherichia coli, is cleaved in vitro to phosphatidic acid and CMP by a membrane-bound hydrolase. Since the physiological function of CDP-diglyceride hydrolase is unknown, we have explored the possibility that this enzyme acts in vivo as either a phosphatidyl- or cytidylyltransferase. To distinguish between these two alternatives, partially purified hydrolase was incubated with CDP-diglyceride in the presence of 50% H218O. Analysis of the reaction products by 31P NMR showed that 18O is incorporated exclusively into CMP, suggesting that the enzyme is a cytidylyltransferase. This conclusion is further supported by the following experimental results: (i) the hydrolase catalyzes the transfer of CMP from CDP-diglyceride to Pi; (ii) numerous phosphomonoesters, such as glycerol 3-phosphate, phosphoserine, and glucose 1-phosphate also function as CMP acceptors, but the corresponding compounds lacking the phosphate residues are not substrates for the enzyme; and (iii) CDP-diglyceride hydrolase exchanges [32P]phosphatidic acid for the phosphatidyl moiety of CDP-diglyceride and 32Pi for the beta-phosphate residue of CDP, indicating the involvement of a novel CMP-enzyme complex. These data suggest a biosynthetic role for CDP-diglyceride hydrolase, and extend the possible functions of CDP-diglyceride in the E. coli envelope.

Chloroform↗
PubMed1974

Heptose-containing pentaglycosyl diglyceride among the lipids of Acholeplasma modicum.

A pentaglycosyl diglyceride with the tentative structure of galactosyl-galactosyl-mannoheptosyl-glucosyl-glucosyl diglyceride was found to be the major glycolipid in Acholeplasma modicum. The heptose is d-glycero-d-mannoheputose. The diglyceride-terminating moiety possesses the structure O-alpha-d-glucopyranosyl-(1 --> 2)-O-alpha-d-glucopyranosyl-sn-1,2-diglyceride. Other glycolipids occurring in this organism are a diglucosyl diglyceride and a monoglucosyl diglyceride with structures identical to the terminal segments of the pentaglycosyl diglyceride. More fully acylated derivatives of these two glycolipids also occur. The phospholipids are all of the glycerophosphoryl type. The neutral lipids are composed of diglycerides and four polyterpenes. The polyterpenes consist of both colored and colorless carotenoids and become radiolabeled with both [(14)C]acetate and [(14)C]mevalonate.

Acetates↗
PubMed1984

CDP-diglyceride hydrolase from pig liver mitochondria.

A CDP-diglyceride hydrolase activity, measured by the release of [3H]CMP from labeled CDP-diglyceride, has been identified in pig liver mitochondria. A modified preparatory method for the synthesis of [3H]CDP-diglyceride of high specific activity and purity is also reported. Activity of the hydrolase is enriched 2.5-fold in mitochondrial membranes (over whole mitochondria) and can be solubilized by nonionic detergents such as Triton X-100 with further enrichment of activity (i.e., 7.9-fold). The CDP-diglyceride hydrolase has a Km of 12.8 microM for CDP-diglyceride and a broad pH range with optimum activity at approximately pH 6.2. Of the CDP-diglycerides tested, the hydrolytic rate is highest for dioleoyl CDP-diglyceride. Activity is inhibited by all divalent cations in whole mitochondria, except in the presence of phosphatidylglycerol in which CMP release is stimulated by Co2+ and Mn2+. The increase in CMP release in the presence of Co2+ or Mn2+ can be accounted for entirely by diphosphatidylglycerol synthase activity which requires either cation. This effect is not seen in Triton X-100 solubilized mitochondrial membranes which contain no diphosphatidylglycerol synthase. All preparations are inhibited by mixed phospholipids (Asolectin) and by Trixon X-100 which abolishes activity completely at concentrations greater than 0.5% (w/v). CDP-diglyceride hydrolase is also inhibited by AMP (46%) and by cytidine nucleotides (CTP greater than CDP greater than cytidine) except CMP. A role for this activity in the regulation of biosynthesis of mitochondrial polyglycerophosphatides is proposed.

Animals↗
PubMed1966

Monogalactosyl and digalactosyl diglycerides from heterotrophic, hetero-autotrophic, and photobiotic Euglena gracilis.

The lipid of Euglena gracilis, dark-grown in a complete medium, contained 2% galactose. The lipid of Euglena gracilis, light-grown in either a complete or an inorganic medium, contained 13-14% galactose. Pure monogalactosyl and digalactosyl diglyceride fractions, isolated by column plus thin-layer chromatography, contained 50% of the lipid-bound galactose of dark-grown cells, and 80% of that of light-grown cells. Molar ratios of monogalactosyl to digalactosyl compounds ranged from 2 to 3. The results show that galactosyl diglycerides, stored in large amount in light-grown cells, persist in small amount in the dark-grown cells. Fatty acids in both the monogalactosyl and the digalactosyl diglycerides were mainly of the 16- and 18-carbon varieties, with high proportions of trienes. The monogalactosyl diglycerides were rich in hexadecatetraenoic acid. Strictly photobiotic cells had twice as much hexadecadienoic and hexadecatetraenoic acids in their monogalactosyl diglycerides, and three times as much hexadecadienoic and octadecadienoic acids in their digalactosyl diglycerides as did illuminated cells grown in a complete medium. Dark-grown (obligate) heterotrophs contained galactosyl diglycerides with high percentages of monoenes. Great compositional variations in the galactosyl diglycerides are thus induced by light and also by nonlipid exogenous metabolites.

Chromatography↗
PubMed1975

Biosynthesis of mitochondrial phospholipids using endogenously generated diglycerides.

When isolated mitochondria or microsomes from rat liver were treated with phospholipase C, the incorporation of radioactive phospholipid precursors was markedly enhanced, presumably as a result of production of diglycerides by hydrolysis of endogenous phospholipids. Incorporation of CDP[14C]choline into lecithin in rat liver or BHK-21 mitochondria could be attributed to residual contamination from elements of the endoplasmic reticulum, with added diglycerides or with endogenous diglycerides produced by the phospholipase C treatment. A similar stimulation of [gamma32P]ATP incorporation into phospholipids was observed with exogenous or endogenous diglycerides, but the mitochondrial diglyceride kinase in either case was also related to the degree of microsomal contaminants. It was concluded that previous studies showing negligible capacity of mitochondria for lecithin biosynthesis de novo were not explainable on the basis of limited accessibility of added diglycerides, and that formation of phosphatidic acid by diglyceride kinase was not of significance in rat liver mitochondria.

Adenosine Triphosphate↗
PubMed1975

Identification of cytidine diphosphate-diglyceride in the pineal gland of the rat and its accumulation in the presence of DL-propranolol.

CDP-diglyceride, an important metabolic intermediate in the biosynthesis of phospholipids, has been isolated for the first time from a mammalian tissue. The isolated material, labeled in incubations of intact rat pineal glands with 32P, [3H]cytidine, or [3H]CTP in the presence of DL-propranolol, was chromatographically identical with authentic CDP-diglyceride and was able to serve as phosphatidyl donor in the enzymatic synthesis of phosphatidylinositol and phosphatidyglycerol. It yielded the expected products upon enzymatic and chemical degradation. No dCDP-diglyceride was detected No radioactive CDP-diglyceride was detected following incubations in the absence of propranolol. Stimulation of CDP-diglyceride labeling from 32P1 occurred at propranolol concentrations between 0.03 and 1.0 mM. Net synthesis of the liponucleotide was shown. At 0.1 mM, propranolol incrased the incorporation of radioactivity into phosphatidylglycerol, phosphatidylinositol, and phosphatidic acid. When inositol (10 mM) and propranolol (0.1 mM) were both present, phosphatidylinositol labeling was further increased, wheas stimulation of phosphatidylglycerol and CPD-diglyceride labeling was abolished. Since CDP-diglyceride did not accumulate in the absence of the drug, its availability may normally be the limiting factor in phosphatidylinositol and phosphatidylglycerol biosynthesis. When propranol is present, inositol may become limiting and thus may lead to the observed labeling pattern.

Animals↗
PubMed1975

Phosphatidylkojibiosyl diglyceride. The covalently linked lipid constituent of the membrane lipoteichoic acid from Streptococcus faecalis (faecium) ATCC 9790.

Water-soluble [14C]glycerol-labeled lipoteichoic acid isolated from the membrane preparations of Streptococcus faecalis (faecium) ATCC 9790 released chloroform-soluble radioactivity upon mild acid hydrolysis. Chromatography of the radioactive, chloroform-extractable material revealed the presence of a very polar lipid (lipid I). Depending upon the conditions of acid hydrolysis, lipid I accounted for as much as 92% of the total 14C-labeled lipids released. More stringent conditions of acid hydrolysis reduced the amount of lipid I and increased the quantity of the other lipids. Lipid I on further mild acid hydrolysis yielded phosphatidylkojibiosyl diglyceride almost quantitively. The other lipids released from the lipoteichoic acid were kojibiosyl diglyceride, monoglucosyl diglyceride, monoglyceride, diglyceride, and phosphatidylmonoglucosyl diglyceride. These lipids are most likely the degradation products of phosphatidylkojibiosyl diglyceride because they are all simpler, structural derivatives of the phosphoglucolipid and they increase in concentration with increasing acid hydrolysis. These and other data demonstrate that the glycerol phosphate polymer of the membrane lipoteichoic acid of S. faecalis (faecium) ATCC 9790 is covalently linked through a phosphodiester bond to phosphatidylkojibiosyl diglyceride.

Carbon Radioisotopes↗
PubMed1975

Phosphatidylkojibiosyl Diglyceride: metabolism and function as an anchor in bacterial cell membrane.

The recently discovered phosphoglycolipid, phosphatidylkojibiosyl diglyceride (PKD), was first observed as a biosynthetic by-product of glycosyl diglyceride metabolism in Streptococcus faecalis (faecium) ATCC 9790. Its structure is 1, 2-diacyl-3-O-alpha-Dglucopyranosyl-6'-O-phosphoryl- [1'', 2''-diacyl-3''-O-sn-glycerol]-alpha-D-glucopyranosyl)-sn-glycerol. The biosynthesis of phosphatidyl-kojibiosyl diglyceride occurs by a novel transphosphatidylation reaction in which a phosphatidyl glycerol to the primary alcohol function at the 6 position of the internal glucose of kojibiosyl diglyceride. The reaction is catalyzed by a membrane-derived enzyme. Phosphatidyl-kojibiosyl diglyceride is bound covalently through a phosphodiester bond to the polyglycerol phosphate moiety of membrane lipoteichoic acid from S. faecalis. Phosphatidylkojibiosyl diglyceride has four nonpolar long chain fatty acyl groups and appears to have the necessary physico-chemical properties to anchor the long hydrophilic glycerol phosphate polymer of lipoteichoic acid to the hydrophobic enviroment of the membrane of S. faecalis and probably other gram-positive bacteria as well.

Cell Membrane↗
PubMed1983

Biosynthesis of D-alanyl-lipoteichoic acid: role of diglyceride kinase in the synthesis of phosphatidylglycerol for chain elongation.

Lipophilic and hydrophilic D-alanyl-lipoteichoic acids are elongated in Lactobacillus casei by the transfer of sn-glycerol 1-phosphate units from phosphatidylglycerol to the poly(glycerophosphate) moiety of the polymer. These sn-glycerol 1-phosphate units are added to the end of the poly(glycerophosphate) which is distal to the glycolipid anchor; 1,2-diglyceride results from this addition. The presence of a diglyceride kinase was suggested by the ATP-dependent phosphorylation of 1,2-diglyceride to phosphatidic acid. Inorganic phosphate was used to initiate the synthesis of lipophilic lipoteichoic acid (LTA) and the elongation of both lipophilic and hydrophilic LTA. Three observations suggest that phosphate and other anions play a role in the in vitro synthesis of LTA and its precursors. First, the conversion of 1,2-diglyceride to phosphatidic acid by diglyceride kinase was stimulated. Second, the synthesis of phosphatidylglycerol was increased. Third, the elongation of lipophilic and hydrophilic LTA was enhanced. These observations indicated that one effect of phosphate might be to enhance the utilization of 1,2-diglyceride for the synthesis of phosphatidic acid. This phospholipid is a precursor of phosphatidylglycerol, the donor of sn-glycerol 1-phosphate for elongation of LTA.

Adenosine Triphosphate↗