PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “GLYCEROPHOSPHATES”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 703 records · Page 39Linked to original sources
PubMed1982

Glycerolipid biosynthesis in rat adipose tissue. 10. Changes during a starvation and re-feeding cycle.

Effects of starvation and re-feeding on adipocyte glycerolipid formation were investigated in young (age 48-55 days) and old rats (age 83-94 days). Adipocyte homogenates were used to assay glycerophosphate acyltransferase and Mg2+-dependent phosphatidase phosphohydrolase. Glycerophosphate acyltransferase was measured in the presence of [14C]glycerol 3-phosphate, palmitate, ATP, CoA and Mg2+. The release of inorganic phosphate from aqueous dispersed phosphatidase was taken as a measure of phosphatidate phosphohydrolase activity. Young rats starved for 48-72 h showed a 2-fold decline in the glycerophosphate acyltransferse activity. Older rats did not show any change in the glycerophosphate acyltransferase activity during 96 h starvation. Re-feeding of starved rats with chow for 48 h caused significant increases in the glycerophosphate acyltransferase activity. These changes were mainly limited to N-ethylmaleimide-sensitive glycerophosphate acyltransferase activity. These changes were mainly limited to N-ethylmaleimide-sensitive glycerophosphate acyltransferase. Phosphatidate phosphohydrolase activity decreased significantly (2-fold) during starvation in both young and old rats. Phosphatidate phosphohydrolase activity was regained completely after re-feeding of starved rats. Initial changes in the glycerophosphate acyltransferase and phosphatidate phosphohydrolase activities were very slow. Most notable increases in the glycerophosphate acyltransferase and phosphatidate phosphohydrolase activities were observed between 24 and 48 h after initiation of a re-feeding schedule. Mean adipocyte size decreased during starvation of rats for 72 h. Although considerable increases in the activities of both glycerophosphate acyltransferase and phosphatidate phosphohydrolase were apparent by re-feeding of starved rats for 48 h, mean adipocyte size did not change during this period. Thus, enzyme changes which occurred after re-feeding were independent of the adipocyte size. To separate the effects of age from the cell size on adipocyte glycerolipid formation during starvation and re-feeding periods, adipocytes from older rats were subjected to filtration through a nylon screen to obtain adipocytes of similar sizes. These studies suggest that the age of the animal significantly influences the effects of starvation and re-feeding on adipocyte glycerolipid formation.

Adipose Tissue↗
PubMed1989

The regulatory effect of phosphates on bone metabolism in vitro.

One of the most important indicators in vitro of the bone-cell phenotype is the synthesis of mineralized bone-like tissue. This has been achieved by supplementing isolated bone-cell and tissue cultures with organic phosphates, in particular, beta-glycerophosphate. To analyze the effects of beta-glycerophosphate on bone-cell metabolism and osteogenesis in vitro, both biochemical analyses and computer-assisted morphometry were used. Simultaneous autoradiographic and histochemical analyses of proliferating and alkaline phosphatase-positive cells were used to measure osteogenic events at the cellular level. Morphometric data showed that beta-glycerophosphate-treated cultures mineralized, but exhibited significantly less bone matrix (P less than 0.05) than non-mineralizing controls. Cultures treated with inorganic phosphate failed to mineralize. Cellular proliferation was unaffected by beta-glycerophosphate; however, there was a decrease in the amount of 3H-thymidine incorporation into the DNA of beta-glycerophosphate-treated cells as detected by autoradiography. The percentage of alkaline phosphatase-positive cells was identical in beta-glycerophosphate-treated or control cultures. In agreement with previous biochemical results, there was a decrease in the amount of alkaline phosphatase enzyme activity per cell. The kinetics of alkaline phosphatase enzymes were measured on individual cells by microdensitometry. beta-Glycerophosphate-treated cultures exhibited more rapid reaction rates than control cultures (p less than 0.05). Taken together, the results suggest that beta-glycerophosphate has global effects on bone-cell metabolism in vitro including its importance in mineralization.

Alkaline Phosphatase↗
PubMed1986

Phosphate compounds as iron chelators in animal cell cultures.

We have studied the capacity of a number of phosphate compounds to act in the double role as a phosphate source and a detoxifier of ferric chloride hydroxo compounds, i.e. as Fe(III) chelators. The tested compounds were: orthophosphate, trimetaphosphate, alpha-glycerophosphate, beta-glycerophosphate, phytic acid, and phosphorylcholine; the test organism the ciliate protozoon Tetrahymena thermophila, an animal cell; and the nutrient medium was synthetic, consisting solely of low-molecular-weight compounds. We assessed growth rates of cells in two experimental series. First, phosphate-starved cells were exposed to the tested phosphate compound as the only phosphate source and the ferric chloride concentrations were varied stepwise from 0 to 1000 microM. Second, we offered the cells orthophosphate as a phosphate source and selected phosphate compounds as chelators. The cell growth results allow the following conclusions: orthophosphate, trimetaphosphate, alpha-glycerophosphate, and beta-glycerophosphate are excellent phosphate sources; trimetaphosphate, alpha-glycerophosphate, beta-glycerophosphate, and phytic acid are excellent Fe(III) chelators; of the tested compounds trimetaphosphate, alpha-glycerophosphate, and beta-glycerophosphate are excellent in the double role as a phosphate source and a ferric chloride hydroxo detoxifier, i.e. as a Fe(III) chelator.

Animals↗
PubMed1976

The glycerophosphateacyltransferases and their function in the metabolism of fatty acids.

1. From different studies on the cellular localization, postional specificity, and regulatory properties of acyl-CoA: glycerophosphate acyltransferase (EC 2,3,1.15) AND ACYL-CoA: 1-ACYLGLYCEROPHOSPHATE ACYLTRANSFERASE (EC 2,3,1....) the following conclusions can be drawn: The glycerophosphate acyltransferase is localized in the endoplasmatic reticulum (microsomes) and in the outer membrane of the mitochondria of the animal cell. Its reaction product is 1-acylglycerophosphate (1-lysophosphatidic acid). The mitochondrial enzyme shows a high preference for saturated fatty acids while the microsomal enzyme is less specific (alternatively the microsomes contain more than one glycerophsophate acyltransferase). 2. The 1-acylglycerphosphate acyltransferase is localized in the endoplasmatic reticulum (microsomes) in the animal cell. Possibly a minor fraction of this enzyme is localized to the outer membrane of the mitochondria. This enzyme shows a strong preference for unsaturated fatty acids. 3. Both the microsomal and the mitochondrial dihydroxyacetonephosphate acyltransferase show similar fatty acid specificity as the corresponding glycerophosphate acyltransferases. It cannot be excluded that dihydroxy-acetonephosphate and glycerophosphate are acylated by the same enzymes. 4. The activity of the glycerophosphate acyltransferase(s) in the liver decreases in fasting or fat feeding and increases upon feeding of carbohydrate. The activity of carnitine palmityltransferase varies exacty opposit. These enzymes do not show dietary variations in heart and adipose tissue. 5. Under the otherwise identical conditions the rate of carnitine acylation in isolated mitochondria decreases more than the rate of glycerophosphate acylation when the concentration of palmityl-CoA is reduced. 6. In isolated liver cells (which has lost most of their carnitine) addition of carnitine increases the rate of fatty acid oxidation and decreases the rate of triglyceride formation. 7. Glycerol and fructose lower the rate of fatty acid oxidation, probably by lowering the levels of acyl-CoA and acyl-carnitine in the cells. 8. It is concluded that the relative activities of glycerophosphate acyltranse and carnitine palmityltransferase probably influence the fate of fatty acids in the cell.

Acyltransferases↗
PubMed1969

Glycerol kinase activities in muscles from vertebrates and invertebrates.

1. Glycerol kinase (EC 2.7.1.30) activity was measured in crude extracts of skeletal muscles by a radiochemical method. The properties of the enzyme from a number of different muscles are very similar to those of the enzyme from rat liver. Glycerol kinase from locust flight muscle was inhibited competitively by l-3-glycerophosphate with a K(i) of 4.0x10(-4)m. 2. The activity of glycerol kinase was measured in a variety of muscles from vertebrates and invertebrates in an attempt to explain the large variation in the activity of this enzyme in different muscles. 3. In vertebrates glycerol kinase activities were generally higher in red muscle than in white muscle; the highest activities (approx. 0.2mumole/min./g. fresh wt.) were found in the red breast muscle of some birds (e.g. pigeon, duck, blue tit) whereas the activities in the white breast muscle of the pheasant and domestic fowl were very low (approx. 0.02mumole/min./g.). 4. On the basis of glycerol kinase activities, muscles from insects can be classified into three groups: muscles that have a low enzyme activity, i.e. <0.3mumole/min./g. (leg muscles of all insects studied and the flight muscles of cockroaches and the tsetse fly); muscles that have an intermediate enzyme activity, i.e. 0.3-1.5mumoles/min./g. (e.g. locusts, cockchafers, moths, water-bugs); and muscles that have a high enzyme activity, i.e. >1.5mumoles/min./g. (e.g. bees, wasps, some blowflies). 5. The function of glycerol kinase in vertebrate and insect muscles that possess a low or intermediate activity is considered to be the removal of glycerol that is produced from lipolysis of triglyceride or diglyceride by the muscle. Therefore in these muscles the activity of glycerol kinase is related to the metabolism of fat, which is used to support sustained muscular activity. A possible regulatory role of glycerol kinase in the initiation of triglyceride or diglyceride lipolysis is discussed. 6. The function of glycerol kinase in the insect muscles that possess a high activity of the enzyme is considered to be related to the high rates of glycolysis that these muscles can perform. The oxidation of extramitochondrial NADH, and therefore the maintenance of glycolysis, is dependent on the functioning of the glycerophosphate cycle; if at any stage of flight (e.g. at the start) the rate of mitochondrial oxidation of l-3-glycerophosphate was less than the activity of the extramitochondrial glycerophosphate dehydrogenase, this compound would accumulate, inhibit the latter enzyme and inhibit glycolysis. It is suggested that such excessive accumulation of l-3-glycerophosphate is prevented by hydrolysis of this compound to glycerol; the latter would have to be removed from the muscle when the accumulation of l-3-glycerophosphate had stopped, and this would explain the presence of glycerol kinase in these muscles and its inhibition by l-3-glycerophosphate.

Adenine Nucleotides↗
PubMed2003

Detection of open and closed conformations of tryptophan synthase by 15N-heteronuclear single-quantum coherence nuclear magnetic resonance of bound 1-15N-L-tryptophan.

1-15N-L-Tryptophan (1-15N-L-Trp) was synthesized from 15N-aniline by a Sandmeyer reaction, followed by cyclization to isatin, reduction to indole with LiAlH4, and condensation of the 15N-indole with L-serine, catalyzed by tryptophan synthase. 1-15N-L-Trp was complexed with wild-type tryptophan synthase and beta-subunit mutants, betaK87T, betaD305A, and betaE109D, in the absence or presence of the allosteric ligands sodium chloride and disodium alpha-glycerophosphate. The enzyme complexes were observed by 15N-heteronuclear single-quantum coherence nuclear magnetic resonance (15N-HSQC NMR) spectroscopy for the presence of 1-15N-L-Trp bound to the beta-active site. No 15N-HSQC signal was detected for 1-15N-L-Trp in 10 mm triethanolamine hydrochloride buffer at pH 8. 1-15N-L-Trp in the presence of wild-type tryptophan synthase in the absence or presence of 50 mm sodium chloride showed a cross peak at 10.25 ppm on the 1H axis and 129 ppm on the 15N axis as a result of reduced solvent exchange for the bound 1-15N-L-Trp, consistent with formation of a closed conformation of the active site. The addition of disodium alpha-glycerophosphate produced a signal twice as intense, suggesting that the equilibrium favors the closed conformation. 15N-HSQC NMR spectra of betaK87T and betaE109D mutant Trp synthase with 1-15N-L-Trp showed a similar cross peak either in the presence or absence of disodium alpha-glycerophosphate, indicating the preference for a closed conformation for these mutant proteins. In contrast, the betaD305A Trp synthase mutant only showed a 15N-HSQC signal in the presence of disodium alpha-glycerophosphate. Thus, this mutant Trp synthase favored an open conformation in the absence of disodium alpha-glycerophosphate but was able to form a closed conformation in the presence of disodium alpha-glycerophosphate. Our results demonstrate that the 15N-HSQC NMR spectra of 1-15N-L-Trp bound to Trp synthase can be used to determine the conformational state of mutant forms in solution rapidly. In contrast, UV-visible spectra of wild-type and mutant Trp synthase in the presence of L-Trp with NaCl and/or disodium alpha-glycerophosphate are more difficult to interpret in terms of altered conformational equilibria.

Escherichia coli↗
PubMed1986

Enzymatic bases for the fatty acid positioning in phospholipids of Brevibacterium ammoniagenes.

Positional distribution of fatty acids in phospholipids from Brevibacterium ammoniagenes was analyzed to find that phosphatidylethanolamine consisted mainly of 1-saturated acyl 2-unsaturated acyl species while phosphatidylglycerol consisted mainly of 1-unsaturated acyl 2-saturated acyl species. Three acyltransferase systems were characterized in a membrane preparation--the acylations of glycerophosphate, 1-acyl-glycerophosphate, and 2-acyl-glycerophosphate--which appeared to be catalyzed by different enzymes. The distribution of fatty acids in the phosphatidylethanolamine molecule was not correlated simply with the specificities of these enzymes, but the relatively high specificity for palmitoyl-CoA of the glycerophosphate acyltransferase system to form 2-acyl-glycerophosphate, followed the relatively high specificity for oleoyl-CoA of the 2-acyl-glycerophosphate acyltransferase system, provided a basis for producing the major molecular species of phosphatidylglycerol.

1-Acylglycerol-3-Phosphate O-Acyltransferase↗
PubMed1976

Factors affecting the acyl selectivities of acyltransferases in Escherichia coli.

In Escherichia coli the synthesis of phosphatidic acid from glycerophosphate involves first the intermediate formation of 1-acyl glycerophosphate. This reaction is catalyzed by the membrane-bound acyl-CoA(acyl-ACP):glycerophosphate acyltransferase. The 1-acylglycerophosphate is then converted to phosphatidic acid by acyl-CoA(acyl-ACP):1-acylglycerophosphate acyltransferase (Okuyama, H., and Wakil, S.J. (1973) J. Biol. Chem. 248, 5197-5205). In vitro both acyltransferases utilize various saturated and unsaturated acyl-CoAs at comparable rates, resulting in the incorporation of both saturated and unsaturated fatty acids into position 1 as well as position 2 of the glycerophosphate moiety. Thus, the specificities of acyltransferase systems as compared with regard to the maximal velocities for various acyl-AoAs, do not explain the positional distribution of the individual fatty acid in phospholipid molecules. The selectivities of the acyltransferases for acyl-CoAs are variable depending upon the acceptor concentration. In the presence of both palmitoyl-CoA and oleoyl-CoA and at low concentrations of the acceptors comparable to those found in vivo, the acylation at position 1 of glycerophosphate by acyl-CoA:glycerophosphate acyltransferase showed higher preference for palmitate, whereas the acylation at position 2 by acyl-CoA:1-acylglycerophosphate acyltransferase showed higher selectivity for oleate. In the presence of saturating amounts of the acceptors, the acylation at position 1 or position 2 was less selective for the acyl-CoAs. The ratios of saturated acyl-CoA to unsaturated acyl-CoA also affect the ratios of the fatty acids incorporated in vitro into positions 1 and 2 of phosphatidic acid; relatively more palmitate was incorporated when the proportion of palmitoyl-CoA among the acyl donors was higher and vice versa. Thus, highly selective positioning of various acyl-CoAs observed at lower concentrations of the acceptors in phosphatidic acid synthesis in vitro helps to explain the selective distribution of saturated and unsaturated fatty acids at positions 1 and 2 of glycerophospholipids in the membranes. Another factor, the availability of acyl donors, affects the proportions of different molecular species of phosphatidic acid, which at least partly explains the variability of molecular species of phospholipids found in vivo.

Acyltransferases↗
PubMed1976

Identification of sn-glycero-1-phosphate and phosphoethanolamine residues linked to the membrane-derived Oligosaccharides of Escherichia coli.

A previous report from this laboratory (van Golde, L.M.G., Schulman, H., and Kennedy, E.P. (1973) Proc. Natl. Acad. Sci. U.S.A. 70, 1368-1372) described the discovery in Escherichia coli of a novel class of oligosaccharides, containing glucose as the sole sugar, substituted with glycerophosphate units derived from membrane phospholipids, and with succinic acid in O-ester linkage. These membrane-derived oligosaccharides, comprising about 0.5 to 1.0% of the dry weight of E. coli, represent a family of closely related oligosaccharides that may be subfractionated on anion exchange resins. The present paper describes studies of the oligosaccharide A-1 described by van Golde et al. in the previous report. The glycerophosphate linked to the oligosaccharide in phosphodiester bond is the sn-glycero-1-P enantiomer. This finding strongly supports the previous conclusion that the oligosaccharides are the acceptors of the polar headgroups of membrane phospholipids, since the unesterified glycerophosphate of phosphatidyl glycerol is an sn-glycero-1-P residue, otherwise rare in nature. The glycerophosphate residues in the membrane-derived oligosaccharide are not substituted in the sn-2 or sn-3 positions, since they are readily oxidized by periodate under mild conditions. Alkaline hydrolysis liberates glycerophosphate, and only negligible amounts of free glycerol, consistent with the view that the glycerophosphate residues are linked to glucose units through position 6, unfavorable for the formation of glucose cyclic phosphate intermediates that would eliminate free glycerol. Oligosaccharide A-1 (but not Fraction A-2) contains phosphoethanolamine residues equivalent to 30 to 40% of the total phosphorus. The phosphoethanolamine residues are linked to position 6 of glucose units, as proved by the isolation of glucose 6-phosphate as a product of partial acid hydrolysis.

Alkaline Phosphatase↗