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At least 145 records · Page 8Linked to original sources
PubMed1972

Consequences of glycerol deprivation on the synthesis of membrane components in a glycerol auxotroph of Staphylococcus aureus.

In a glycerol auxotroph of Staphylococcus aureus, the deprivation of glycerol affected the formation of certain membrane components. (i) There was synthesis of fatty acids at the predeprivation rate even though the fatty acids synthesized accumulated as free fatty acids rather than as esterified fatty acids; (ii) there was a complete cessation of phospholipid and vitamin K isoprenologue biosynthesis; (iii) there was conservation of the glycerol esters of the complex phospholipids and glucolipids; (iv) there was an immediate decrease in the rate of synthesis of monoglucoslydiglyceride (30%) and diglucosyldiglyceride (60%); (v) there was a 50% decrease in the rate of synthesis of the polar and nonpolar carotenoids; (vi) there was synthesis of protoheme, heme a, and nonspecific membrane protein at the predeprivation rate; and (vii) there was an abrupt cessation in the formation of new, functional glycine transport activity.

Acetates↗
PubMed1996

Synthesis and evaluation of the antiproliferative effects of 1-O-hexadecyl-2-O-methyl-3-O-(2'-acetamido-2'-deoxy-beta-D- glucopyranosyl)-sn-glycerol and 1-O-hexadecyl-2-O-methyl-3-0- (2'-amino-2'-deoxy-beta-D-glucopyranosyl)-sn-glycerol on epithelial cancer cell growth.

Two ether glucosyl diglyceride analogs were synthesized, and their antiproliferative activity against four epithelial cancer cell lines was evaluated. 1-O-Hexadecyl-2-O-methyl-3-O-(2'-acetamido-2'-deoxy-beta-D- glucopyranosyl)-sn-glycerol (4) was synthesized by reaction of 2-acetamido-2-deoxy-3,4,6-tri-O-acetyl-alpha-D-glucopyranosyl chloride with 1-O-hexadecyl-2-O-methyl-sn-glycerol followed by deacetylation by methanolic hydrolysis. The N-acetyl group of 4 was removed by hydrolysis with ethanolic potassium hydroxide to form 1-O-hexadecyl-2-O-methyl-3-O-(2'-amino-2'-deoxy-beta-D-glucopyranosyl)- sn-glycerol (5). Compounds 4 and 5 inhibited the proliferation of MCF-7, A549, A427, and T84 cancer cell lines. The IC(50) values for 5 ranged from 6.5 to 12.2 microM, whereas 4 was more effective against A549 cells (IC(50) 9 microM) than against MCF-7 (IC(50) 17 microM) and A427 (IC(50) 25 microM) cells and was inactive against T84 cells. Under identical incubation conditions, compounds 4 and 5 were potent inhibitors of the proliferation of OVCAR-3 cells with IC(50) values of 12 and 4 microM, respectively, whereas ET-18-OCH(3), hexadecylphosphocholine, and erucylphosphocholine had IC(50) values of 24, >30, and >30 microM, respectively. The cell-inhibitory profile of these ether-linked glucosyl diglycerides strengthens the hypothesis that such glycolipids represent a distinct group of antitumor ether lipids, having antineoplastic activities that differ from the well-known alkylphosphocholines and alkyllysophospholipids.

Antineoplastic Agents↗
PubMed2003

AtDGK2, a novel diacylglycerol kinase from Arabidopsis thaliana, phosphorylates 1-stearoyl-2-arachidonoyl-sn-glycerol and 1,2-dioleoyl-sn-glycerol and exhibits cold-inducible gene expression.

Diacylglycerol kinase (DGK) phosphorylates diacylglycerol (DAG) to generate phosphatidic acid (PA). Both DAG and PA are implicated in signal transduction pathways. DGKs have been widely studied in animals, but their analysis in plants is fragmentary. Here, we report the cloning and biochemical characterization of AtDGK2, encoding DGK from Arabidopsis thaliana. AtDGK2 has a predicted molecular mass of 79.4 kDa and, like AtDGK1 previously reported, harbors two copies of a phorbol ester/DAG-binding domain in its N-terminal region. AtDGK2 belongs to a family of seven DGK genes in A. thaliana. AtDGK3 to AtDGK7 encode approximately 55-kDa DGKs that lack a typical phorbol ester/DAG-binding domain. Phylogenetically, plant DGKs fall into three clusters. Members of all three clusters are widely expressed in vascular plants. Recombinant AtDGK2 was expressed in Escherichia coli and biochemically characterized. The enzyme phosphorylated 1,2-dioleoyl-sn-glycerol to yield PA, exhibiting Michaelis-Menten type kinetics. Estimated K(m) and V(max) values were 125 microm for DAG and 0.25 pmol of PA min(-1) microg(-1), respectively. The enzyme was maximally active at pH 7.2. Its activity was Mg(2+)-dependent and affected by the presence of detergents, salts, and the DGK inhibitor R59022, but not by Ca(2+). AtDGK2 exhibited substrate preference for unsaturated DAG analogues (i.e. 1-stearoyl-2-arachidonoyl-sn-glycerol and 1,2-dioleoyl-sn-glycerol). The AtDGK2 gene is expressed in various tissues of the Arabidopsis plant, including leaves, roots, and flowers, as shown by Northern blot analysis and promoter-reporter gene fusions. We found that AtDGK2 is induced by exposure to low temperature (4 degrees C), pointing to a role in cold signal transduction.

Amino Acid Sequence↗
PubMed1990

Multiple regulatory elements for the glpA operon encoding anaerobic glycerol-3-phosphate dehydrogenase and the glpD operon encoding aerobic glycerol-3-phosphate dehydrogenase in Escherichia coli: further characterization of respiratory control.

In Escherichia coli, sn-glycerol-3-phosphate can be oxidized by two different flavo-dehydrogenases, an anaerobic enzyme encoded by the glpACB operon and an aerobic enzyme encoded by the glpD operon. These two operons belong to the glp regulon specifying the utilization of glycerol, sn-glycerol-3-phosphate, and glycerophosphodiesters. In glpR mutant cells grown under conditions of low catabolite repression, the glpA operon is best expressed anaerobically with fumarate as the exogenous electron acceptor, whereas the glpD operon is best expressed aerobically. Increased anaerobic expression of glpA is dependent on the fnr product, a pleiotropic activator of genes involved in anaerobic respiration. In this study we found that the expression of a glpA1(Oxr) (oxygen-resistant) mutant operon, selected for increased aerobic expression, became less dependent on the FNR protein but more dependent on the cyclic AMP-catabolite gene activator protein complex mediating catabolite repression. Despite the increased aerobic expression of glpA1(Oxr), a twofold aerobic repressibility persisted. Moreover, anaerobic repression by nitrate respiration remained normal. Thus, there seems to exist a redox control apart from the FNR-mediated one. We also showed that the anaerobic repression of the glpD operon was fully relieved by mutations in either arcA (encoding a presumptive DNA recognition protein) or arcB (encoding a presumptive redox sensor protein). The arc system is known to mediate pleiotropic control of genes of aerobic function.

Anaerobiosis↗
PubMed1990

A comparison of absorption of glycerol tristearate and glycerol trioleate by rat small intestine.

Generally, fats rich in saturated fatty acids raise serum cholesterol, whereas fats rich in polyunsaturated fatty acids lower it. There appear to be exceptions; e.g., stearic acid (18:0)-rich fats have little or no effect on serum cholesterol concentrations. This apparent lack of cholesterolemic effect of stearic acid-rich fat could be because intestinal absorption of fat is poor or subsequent plasma and/or tissue metabolism of fat is different. To investigate mechanisms involved, we compared intestinal digestion, uptake, and lymphatic transport of glycerol tristearate (TS) and glycerol trioleate (TO, 18:1). Two groups of rats bearing intestinal lymph fistulas were used. TO rats were fed intraduodenally for 8 h at a constant rate a lipid emulsion of 25 mumols/h of TO (labeled with glycerol tri[9,10 (n)-3H]oleate), 7.8 mumols of egg phosphatidylcholine, and 57 mumols of sodium taurocholate in 3 ml of phosphate-buffered saline. TS rats were fed the same lipid emulsion except that TS replaced TO and the emulsion was labeled with glyceryl [1,3-14C]tristearate. The lymph triglyceride and radioactivity were determined. After infusion, the luminal and mucosal radioactive lipid content was analyzed. The results showed that there was significantly less lipid transported in the lymph of TS rats compared with TO rats. The results also showed a significant decrease in the absorption of TS as compared with TO. This was due in part to poor lipolysis. In addition, the lipid absorbed by the intestine of the TS rats was transported into lymph less efficiently than in TO rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2001

Synthesis and hydrolytic behaviour of glycerol-1,2-diibuprofenate-3-nitrate, a putative pro-drug of ibuprofen and glycerol-1-nitrate.

Nitroxylated derivatives of non-steroidal anti-inflammatory drugs appear to offer protection against the gastrotoxicity normally associated with non-steroidal anti-inflammatory drugs, ostensibly via local production of nitric oxide. A diester of ibuprofen and glycerol-1-mononitrate has been prepared via the condensation of ibuprofen with 3-bromopropan-1,2-diol, followed by silver-(I)-nitrate-mediated nitroxylation. The release of ibuprofen from this diester has been studied in a simulated gastric fluid model with direct analysis by reverse-phase HPLC, using an acetonitrile-water (80%:20%) mobile phase containing trifluoroacetic acid (0.005%). n-Propyl ibuprofen was found to undergo pH-dependent hydrolysis, ranging from negligible hydrolysis at pH 5 to 52% hydrolysis at pH 3, over a 2-h period in this model. The ibuprofen-glycerol mononitrate diester was subjected to the most vigorous model hydrolytic conditions and was found to undergo 50 % hydrolysis during the study period. This study shows that pro-drugs of ibuprofen and glycerol mononitrate can be obtained, and can undergo degradation to the parent drugs under conditions simulating those likely to be encountered in the stomach.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2004

Distinct intracellular localization of Gpd1p and Gpd2p, the two yeast isoforms of NAD+-dependent glycerol-3-phosphate dehydrogenase, explains their different contributions to redox-driven glycerol production.

During anaerobiosis Saccharomyces cerevisiae strongly increases glycerol production to provide for non-respiratory oxidation of NADH to NAD(+). We here report that respiratory-deficient cells become strictly dependent on the Gpd2p isoform of the NAD(+)-linked glycerol-3-phosphate dehydrogenase (Gpd). The growth inhibition of respiratory incompetent cox18Delta cells lacking GPD2 is reversed by the addition of acetoin, an alternative sink for NADH oxidation. Growth is also restored by addition of lysine or glutamic acid/glutamine, the synthesis of which involves production of mitochondrial NADH. Lysine produced a stronger growth stimulating effect than glutamic acid consistent with an upregulated expression of the IDP3 gene for peroxisomal synthesis of the glutamate precursor alpha-ketoglutarate. Gpd2p is known to be a cytosolic protein but possesses a classical mitochondrial presequence, which we show is sufficient for mitochondrial targeting. A partial mitochondrial localization of Gpd2p will provide for establishment of intramitochondrial redox balance under non-respiratory conditions. Gpd1p, the other Gpd isoform, is partly cytosolic and partly peroxisomal and becomes more strictly peroxisomal in respiratory-deficient mutants. The different cellular distribution of Gpd1p and Gpd2p thus appears to be the main reason Gpd1p cannot substitute for Gpd2p in cox18Deltagpd2Delta cells, despite similar kinetic characteristics of the two iso-enzymes.

Acetoin↗
PubMed1992

Structure and regulation of the glpFK operon encoding glycerol diffusion facilitator and glycerol kinase of Escherichia coli K-12.

The glpFK operon maps near minute 88 on the linkage map of Escherichia coli K-12 with glpF promoter proximal. The glpF gene encodes a cytoplasmic membrane protein which facilitates the diffusion of glycerol into the cell. The glpK gene encodes glycerol kinase. In the present work, the nucleotide sequence of the 5'-end of the operon, including the control region, the glpF gene, and part of the glpK gene, was determined. The facilitator was predicted to contain 281 amino acids with a calculated molecular weight of 29,780. It is a highly hydrophobic protein with a minimum of six potential transmembrane alpha helices. The transcription start site for the glpFK operon was located 71 base pairs upstream from the proposed translation start codon for glpF. Preceding the transcription start site were sequences similar to the -10 and -35 consensus sequences for bacterial promoters. Binding sites for the cAMP-cAMP receptor protein (CRP) complex and the glp repressor were identified by DNase I footprinting. The region protected by the cAMP.CRP complex contained tandem sequences resembling the consensus sequence for CRP binding. The CRP sites were centered at 37.5 and 60.5 base pairs upstream of the start of transcription. The glp repressor protected an extensive area (-89 to -7 relative to the start point of transcription), sufficient for the binding of four repressor tetramers. Two additional binding sites for the repressor were identified within the glpK coding region. The DNA containing these two operators synergistically increased the apparent affinity of glp repressor for DNA fragments containing the four operators in the promoter region of the glpFK operon. With this study, a total of 13 operators for the glp regulon have been characterized. Comparison of these operators revealed the consensus 5'-WATGTTCGWT-3' for the operator half-site (W = A or T). The relative affinity of the glp repressor for the various glp operators was assessed in vivo using a promoter-probe vector. The relative apparent affinity of the control regions for glp repressor was glpFK greater than glpD greater than glpACB greater than glpTQ. The degree of catabolite repression for each of the operons was assessed using a similar system. In this case, the relative sensitivity of the glp operons to catabolite repression was glpTQ greater than glpFK greater than glpACB greater than glpD.

Amino Acid Sequence↗
PubMed1992

Application of glycerol to freezing bovine pancreas. Part 3. Effects of freezing rate and glycerol addition on changes in pancreas proteins.

Changes in protein solubility, amino nitrogen and activity of proteases in bovine pancreas frozen at -70 and -18 degrees C after soaking in various aqueous glycerol solutions were studied. Reduction of freezing temperature causes decrease of value in all studied parameters. Additionally, an inhibitory effect of glycerol on protease activity was demonstrated.

Animals↗
PubMed1989

Muscle glycerol kinase in Duchenne dystrophy and glycerol kinase deficiency.

The complex glycerol kinase deficiency (GKD) syndrome is an X-linked recessive genetic disorder. The syndrome often includes a myopathy that is similar histologically to Duchenne muscular dystrophy (DMD). The glycerol kinase (GK) locus is in the Xp21 region in the midportion of the short arm of the X chromosome and is in close proximity to the DMD locus. We have investigated GK activity and subcellular distribution of muscle GK in DMD patients and in a patient with the complex GKD syndrome presenting with myopathy. We found no abnormality of muscle GK specific activity or subcellular distribution in DMD. In the patient with the complex GKD syndrome the specific activity and kinetics of muscle GK were normal, but the subcellular distribution of muscle GK was altered. Liver GK had less than 10% of normal activity and showed markedly altered kinetics. These findings indicate that there is no abnormality of muscle GK activity in DMD muscle. Furthermore, the normal GK activity in an individual with the complex GKD syndrome suggests that muscle and liver GK are genetically distinct. These findings support the concept that the complex GKD syndrome results from small deletions that affect closely linked but separate loci for DMD, GK and adrenal hypoplasia.

Adolescent↗
PubMed1986

Clinical value of dual-isotope fat absorption test system (FATS) using glycerol [125I]trioleate and glycerol [75Se]triether.

In order to delineate the clinical value of a dual-isotope fat absorption test system (FATS) using glycerol [75Se]triether as lipid-phase marker and glycerol [125I]trioleate as the test lipid, fecal isotope ratios from single stools (and a 72-hr stool homogenate) were compared to quantitative fecal fat excretion. The study included 11 patients without and 24 patients with steatorrhea. With a figure of 0.8% as the upper limit of normal, the test was a reliable indicator of steatorrhea with 87.5% sensitivity and 81.8% specificity; efficiency was 85.7%. Related to a prevalence of steatorrhea of 45.9% as the mean value of 1269 consecutive 72-hr specimens investigated for steatorrhea during 1978-1982, the positive (negative) predictive value of the FATS is 80.3% (87.2%). With 2% as the upper limit of normal, no false positive results ensued. It is concluded that a two-step interpretation of the FATS (0.8% limit and 2% limit) may be regarded a valid qualitative index for steatorrhea. The FATS isotope ratio using single stools correlated well with FATS ratios in the 72-hr stool homogenates (r = 0.97). FATS therefore allows a convenient estimate of steatorrhea from measuring single stools. As a quantitative measure of fecal fat excretion, the FATS is unreliable.

Adult↗
PubMed2002

Action of 1-(11-selenadodecyl)-glycerol and 1-(11-selenadodecyl)-3-trolox-glycerol against lipid peroxidation.

The antioxidant action on lipid peroxidation of the synthesized selenium compounds 1-(11-selenadodecyl)-glycerol (SeG) and 1-(11-selenadodecyl)-3-Trolox-glycerol (SeTrG, where Trolox = 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid) was investigated. We compared the reactivity of the selenium compounds toward peroxyl radicals and their inhibitory effect on lipid peroxidation, induced by several kinds of initiating species such as azo compounds, metal ions, and superoxide/nitric oxide in solution, micelles, membranes, and rat plasma. SeTrG, but not SeG, scavenged peroxyl radicals. SeG reduced methyl linoleate hydroperoxides in organic solution and in methyl linoleate micelles oxidized by ferrous ion (Fe2+)/ascorbic acid. In rat plasma SeG and SeTrG decreased the formation of lipid hydroperoxides generated by hydrophilic azo compounds. SeG and SeTrG spared alpha-tocopherol (alpha-TOH) consumption in multilamellar vesicle membranes oxidized by hydrophilic or lipophilic initiators, and only SeTrG spared alpha-TOH in superoxide/nitric oxide oxidized membranes. In rat plasma oxidized by radical initiators (either hydrophilic or lipophilic) or superoxide/nitric oxide, SeTrG suppressed alpha-TOH consumption, but SeG had no effect. The two selenium-containing compounds showed inhibitory effects on lipid peroxidation that depended on their structure, the medium where they acted, and the oxidant used.

Animals↗
PubMed1977

Study of the mechanism of action of adenosylcobalamindependent glycerol dehydratase from Aerobacter aerogenes. II. The inactivation kinetics of glycerol dehydratase complexes with adenosylobalamin and its analogs.

The inactivation kinetics of vacterial glycerol dehydratase (EC 4.2.1.30) in the course of its reaction with adenosylcobalamin (AdoCbl) and its analogs were investigated. It was shown that the inactivation rate of apoenzyme complexes with AdoCbl analogs is determined by the nature of the analogs employed and probably by the rate of their conversion into hydroxycobalamins. A possible inactivation mechanism of glycerol dehydratase is discussed.

Apoenzymes↗
PubMed1980

Measurement of fat absorption using [3H]glycerol triether and [14C]glycerol trioleate in man.

A direct test of lipid absorption has been developed using [3H]glycerol triether as a lipid marker and [14C]glycerol trioleate as the test lipid. Percentage absorption of triolein is calculated from the isotope ratio ingested and excreted in faeces. The test is independent of a complete faecal collection, reproducible and shows little day to day variation. Absorption in 25 normal subjects ranged from 96.4--100% (mean 98.6, S.D. +/- 1.15). In 24 patients with known pancreatic or small intestinal disease and steatorrhoea absorption ranged from 0.01% to 89.9%. The test has also been assessed by comparison with a standard Lundh test and faecal fat estimation in 34 patients.

Adult↗
PubMed1997

A point mutation in the glycerol kinase gene associated with a deletion in the dystrophin gene in a familial X-linked muscular dystrophy: non-contiguous gene syndrome involving Becker muscular dystrophy and glycerol kinase loci.

We report a family with an X-linked recessive muscular dystrophy characterised by exercise-induced myalgia, recurrent pigmenturia and mild proximal muscle involvement. Immunocytochemical and immunoblotting analysis in muscle, using the antibody directed against the rod domain of dystrophin, revealed a loss of immunoreactivity, but the immunolabelling using the antibodies directed against the COOH and NH2 domains of dystrophin were almost normal. The immunoreactions for alpha-sarcoglycan, gamma-sarcoglycan and beta-dystroglycan were normal. In the five male patients of this family with increased serum creatine kinase levels (from x8 to x50), mass spectrometry screening of the urine revealed a large increase in glycerol elimination which was quantified by enzymatic assay (from x14 to x39). An in-frame deletion of the dystrophin gene (exons 13-29) was found in the same five males and in three carrier females. All the deleted chromosomes also carried a missense mutation at nucleotide 947 of the Xp glycerol kinase (GK) gene resulting in a Thr to Met substitution at codon 278. These findings indicate that the two mutations cosegregate on the same chromosome in this family. This is the first reported case of two physically independent mutations, within the DMD and GK genes, which are contiguous but several hundred kilobases apart.

Adolescent↗
PubMed2005

Relaxation dynamics in glycerol-water mixtures: I. Glycerol-rich mixtures.

We discuss the relaxation dynamics of glycerol-water mixtures, as studied by dielectric spectroscopy in the frequency range from 1 Hz to 250 MHz and at temperatures between 173 and 323 K. The experimental results obtained for the glycerol-rich mixtures suggest that the main dielectric relaxation process, as well as the so-called high-frequency "excess wing" (EW) and dc conductivity, follow the same temperature dependence. This result indicates that all of these processes are induced by the same molecular origin. A new phenomenological function is proposed to describe the whole dielectric spectrum in the covered frequency range, and some possible mechanisms of dielectric behaviors through the dc conductivity, the main relaxation process, and the EW are discussed.

Glycerol↗
PubMed2003

Water and glycerol permeation through the glycerol channel GlpF and the aquaporin family.

The 2.2 A resolution crystal structure of GlpF, an E. coli aquaporin that facilitates the flow of glycerol, water and other small solutes, provides much insight into the molecular function and selectivity of aquaporins. Using GlpF and its atomic structure as a paradigm for the ten highly conserved human aquaporins, site-directed mutagenesis has been used to mutate residues that are possibly integral to the structure and function of different aquaporins. X-ray crystallography and other biophysical and molecular simulation methods allows for assessment of these changes at the structural and functional level. Initial attempts to convert the glycerol specific properties of GlpF towards a water specific aquaporin resulted in the shifting of GlpF channel properties towards that of the water aquaporins. This result reveals the great possibility of emulating and deciphering the function of other aquaporins with GlpF via mutagenesis and investigation of structure and function.

Aquaporins↗