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PubMed1981

Intracellular monosaccharide and amino acid concentrations and activities and the mechanisms of insulin action.

Current amino acid and monosaccharide transport models are based on an assumption which equates the intracellular chemical activity of a solute with its concentration. This assumption was tested for alpha-aminoisobutyric acid and 3-O-methylglucose in a giant cell, the amphibian oocyte, by using recently developed cryomicrodissection and internal reference phase techniques. We found the following. (i) alpha-Aminoisobutyric acid and 3-O-methylglucose activities were much greater in cytoplasm than was suggested by concentration data; i.e., activity coefficients were higher than in ordinary water solutions. This is attributable to the inaccessibility of considerable water as solvent (solute exclusion). (ii) Solute concentrations varied regionally as follows: nucleus > > animal cytoplasm > vegetal cytoplasm. Insulin increased the nucleus/cytoplasm concentration asymmetry, apparently by increasing cytoplasmic solute exclusion. (iii) Nuclear activity coefficients more closely resembled those of ordinary saline solutions so that nucleus/ extracellular concentration ratios reflected transmembrane activity gradients better than did cytoplasm (or whole cell)/extracellular ratios. (iv) Mediated passive alpha-aminoisobutyric acid and 3-O-methylglucose transport were constituent oocyte membrane properties. Membrane active transport was initiated with time (in the presence of substrate) and by insulin. (v) Increased temperature mimicked insulin in enhancing transmembrane alpha-aminoisobutyric acid activity gradients and increasing the nucleus/cytoplasm concentration asymmetry. These results indicated that concentration data are a misleading measure of cellular amino acid and monosaccharide activity; some consequences of this observation were explored. A model is proposed in which cell water has reduced solvent capacity or is compartmentalized (considered less likely) and is susceptible to physiological modulation. The model accounts for many observations in small cells, suggesting generality of the exclusion phenomenon and a previously unrecognized metabolic control mechanism.

3-O-Methylglucose↗
PubMed1991

Sialic acid storage diseases. A multiple lysosomal transport defect for acidic monosaccharides.

A defective efflux of free sialic acid from the lysosomal compartment has been found in the clinically heterogeneous group of sialic acid storage disorders. Using radiolabeled sialic acid (NeuAc) as a substrate, we have recently detected and characterized a proton-driven carrier for sialic acid in the lysosomal membrane from rat liver. This carrier also recognizes and transports other acidic monosaccharides, among which are uronic acids. If no alternative routes of glucuronic acid transport exist, the disposal of uronic acids can be affected in the sialic acid storage disorders. In this study we excluded the existence of more than one acidic monosaccharide carrier by measuring uptake kinetics of labeled glucuronic acid [( 3H]GlcAc) in rat lysosomal membrane vesicles. [3H]GlcAc uptake was carrier-mediated with an affinity constant of transport (Kt) of 0.3 mM and the transport could be cis-inhibited or trans-stimulated to the same extent by sialic acid or glucuronic acid. Human lysosomal membrane vesicles isolated from cultured fibroblasts showed the existence of a similar proton-driven transporter with the same properties as the rat liver system (Kt of [3H]GlcAc uptake 0.28 mM). Uptake studies with [3H]NeuAc and [3H]GlcAc in resealed lysosome membrane vesicles from cultured fibroblasts of patients with different clinical presentation of sialic acid storage showed defective carrier-mediated transport for both sugars. Further evidence that the defective transport of acidic sugars represents the primary genetic defect in sialic acid storage diseases was provided by the observation of reduced, half-normal transport rates in lymphoblast-derived lysosomal membrane vesicles from five unrelated obligate heterozygotes. This study reports the first observation of a human lysosomal transport defect for multiple physiological compounds.

Animals↗
PubMed1980

The effect of intestinal solute load on water secretion in infants with acquired monosaccharide intolerance.

The osmotic effect of unabsorbed glucose on intestinal secretion of water and electrolytes was investigated by jejunal perfusion in eight infants ranging from 2 to 17 months of age. All infants had or were recovering from acquired monosaccharide intolerance. Isocaloric solutions of glucose and glucose polymer containing 1% polyethylene glycol as a nonabsorbable marker were tested. The osmolalities of the glucose polymer solutions were 1/3 to 1/6 that of the glucose. No major differences were noted in carbohydrate absorption whereas mean water flux changed from secretion of 0.37 ml/min to absorption of 0.023 ml/min when glucose was replaced by glucose polymer. Sodium and potassium flux followed the same pattern. The results of this study indicate that the increased intestinal secretion in acquired monosaccharide intolerance may be a function of osmolar load in the presence of a reduced absorptive capacity.

Body Water↗
PubMed2004

Ovarian monosaccharides (glucose and fructose): hormonal effects and their role in final oocyte maturation and egg quality in catfish Heteropneustes fossilis, Bloch.

In the catfish H. fossilis, ovarian glucose and fructose levels showed significant annual variations that could be correlated with the gonado-somatic index. The concentration of the sugars, which was low in resting phase of gonad increased with the onset of oogenesis, reaching the peak in prespawning (June) phase. Glucose is the predominant monosaccharide in the late oogenesis, while fructose in early oogenesis and resting phase. Administration of a single injection of HCG (100 IU/fish) decreased glucose at 4 hr but increased fructose (6 hr) in the resting phase. In the preparatory phase (active oogenesis), fructose decreased significantly at 4 hr and glucose at 6 and 12 hr. In the prespawning phase, HCG administration induced a significant decrease in glucose level at 2 hr but increased it significantly at 16 and 18 hr. Fructose concentration, on the other hand, decreased > or = 4 hr. The involvement of different energy substrates (glucose, fructose, 2-deoxyglucose and pyruvate) on final oocyte maturation and viability of eggs were demonstrated in an in vitro study, employing incubation of mature oocytes in medium containing one or the other energy substrates. Glucose at 4 and 8 mM concentrations increased the viability of eggs without affecting germinal vesicle break down (GVBD) and at high concentrations (16 and 32 mM) marginally increased GVBD but decreased viability. Pyruvate at high concentrations (> or = 8 mM) produced a positive effect on both GVBD and viability. Fructose and 2-deoxyglucose did not elicit any effect on these parameters. The results suggest that glucose has an active role in catfish oogenesis and maintaining egg quality and HCG influences monosaccharide metabolism in a season-dependent manner.

Animals↗
PubMed2005

Expression of cytokines and monosaccharide transporters in the duodenal mucosa of patients with gastrointestinal symptoms in rural Thailand.

Levels of cytokines and GLUT family monosaccharide transporters in the duodenal mucosa were examined in patients from Nong Khai, Thailand, who had underwent gastroscopy because of gastrointestinal problems. Duodenal biopsy specimens were collected from a total of 33 patients (24 males and 9 females, 45.0 +/- 13.5 years old). Ten patients had present or recent intestinal helminth infections, including strongyloidiasis, taeniasis or ascariasis (group A), 7 were urease-test positive, indicating Helicobacter pylori infection (group B), and 16 had neither helminth infections nor urea-test positivity (group C). Total RNA was extracted from the biopsied specimens and a semi-quantitative RT-PCR was performed. The positivities for IL-13, IL-5 and IFN-gamma mRNA expressions in the patients were 24.2, 60.6 and 100%, respectively, with the highest IL-13 and IL-5 positivities in group A, followed by group C and B. The IL-5 positive rate was significantly higher among patients with high peripheral blood eosinophil counts (> 4%) than in patients with low peripheral blood eosinophil counts. GLUT-1 and GLUT-5 were detectable in all the patients. Although GLUT-1 expressions did not differ among groups A, B and C. GLUT-5 expressions were significantly lower in group B than in group C. These results indicate that helminth and H. pylori infections result in different immunopathological responses in the duodenal mucosa, lower expressions of type 2 cytokines and monosaccharide transporters in H. pylori infections than in helminth infections.

Adult↗
PubMed1978

[Study of amino monosaccharides by thermoionic detection in gas-liquid chromatography. Application to a pyroglobulin IgM (author's transl)].

The monosaccharides of proteic samples liberated by methanolysis and submitted to trimethylsilylation by the trimethylsilylimidazole (TSIM) are determined by gas-liquid chromatography. The neutral sugars are detected in simple flame ionization (FID) and the amino sugars identified separatively by the use of a thermoionic detector (TID) which responds selectively to nitrogenous and phosphorated compounds. The method described has been tested on standard mixtures of monosaccharides and on a well known glycoprotein : the uromucoid. Then it has been applied to a pyroglobulin IgM (mu2, chi2).

Amino Sugars↗
PubMed1984

[Effect of monosaccharides on net ion fluxes across the sperm membrane. Contribution to capacitation].

Monosaccharide supply, monosaccharide fluxes and ion fluxes play an important role in the process of capacitation of spermatozoa. Therefore we investigated the influence of D-glucose and D-fructose on the net -fluxes of Na+ and Rb+. The Na+ fluxes were very low and showed no alterations, when glucose or fructose were present in the incubation medium. On the other hand the net-Rb+-fluxes, which can be regarded as representative for the net-K+-fluxes, were energy dependent and ouabain-sensitive. Moreover D-glucose and D-fructose increased significantly the affinity of Rb+ towards its transport system. The specifity of these interactions is discussed.

Fructose↗
PubMed1998

Factors that cause the beta-anomeric preference of Na+/glucose cotransporter for intestinal transport of monosaccharide conjugates.

The intestinal transport of glucose- and galactose-conjugated acetaminophen (APAP glycoside) by Na+/glucose cotransporter (SGLT1) was studied. SGLT1-mediated transport of APAP glycosides preferred glucoside>galactoside and beta-anomer>alpha-anomer. These preferences agree with previous studies. NMR spectroscopic and molecular modeling studies indicated that the conformation of the glucose ring of alpha- and beta-glucosides of APAP, as well as glycosides in previous studies, is in the 4C1 chair form, the same form as glucose itself. Molecular dynamics analysis also indicated that the glucose ring was in the 4C1 chair form, and that there are differences between the rotational spaces of aglycones and hydroxy groups of glucose moieties between anomers. Therefore, we conclude that the beta-anomeric preference of glucose conjugate transport by SGLT1 is not due to the conformation of the glucose ring, but to the configuration of the aglycone at C-1 of the monosaccharide moiety.

Acetaminophen↗
PubMed2002

Ethanol impairs monosaccharide uptake and glycosylation in cultured rat astrocytes.

Astrocyte and glial-neuron interactions have a critical role in brain development, which is partially mediated by glycoproteins, including adhesion molecules and growth factors. Ethanol affects the synthesis, intracellular transport, subcellular distribution and secretion of these glycoproteins, suggesting alterations in glycosylation. We analyzed the effect of long-term exposure to low doses of ethanol (30 mm) on glycosylation process in growing cultured astrocytes in vitro. Cells were incubated for short (5 min) and long (90 min) periods with several radioactively labeled carbohydrate precursors. The uptake, kinetics and metabolism of these precursors, as well as the radioactivity distribution in protein gels were analyzed. The levels of GLUT1 and mannosidase II were also determined. Ethanol increased the uptake of monosaccharides and the protein levels of GLUT1 but decreased those of mannosidase II. It altered the carbohydrate moiety of proteins and increased cell surface glycoproteins containing terminal non-reduced mannose. These results indicate that ethanol impairs glycosylation in rat astrocytes, thus disrupting brain development.

Animals↗
PubMed1964

PHOSPHOLIPID-SUGAR COMPLEXES IN RELATION TO CELL MEMBRANE MONOSACCHARIDE TRANSPORT.

Phospholipids extracted from "ghosts" of human erythrocytes or from other sources carry substantial quantities of glucose or other monosaccharides from the dry state into highly nonpolar solvents. Various characteristics of this weak association phenomenon show suggestive parallels with known properties of the mediated sugar-transfer system in the membrane of the intact red cell.

Biological Transport↗
PubMed1981

The monosaccharide transporter of the human erythrocyte. Transport activity upon reconstitution.

The transport function of the purified monosaccharide transporter from human erythrocytes has been investigated. By a cycle of cholate solubilization and removal, the purified transporter was incorporated into phospholipid vesicles of about 300 A diameter, at a density of about one per vesicle. This distribution permitted an all-or-none assay for transport activity, in which the fraction of the intravesicular volume that rapidly equilibrated with D-glucose in the medium yielded an estimate of the moles of protein functional in transport. It was found that almost every transporter molecule capable of binding cytochalasin B was also capable of transport. The rate of transporter-catalyzed exchange of D-glucose between the medium and the vesicles at equilibrium was also measured. In this assay, the transport activity of the purified protein, expressed per mol of cytochalasin B binding of site, was about 5% of that of the transporter in the intact erythrocyte under similar conditions. These results show that the reduced transport activity of the purified transporter found in various rate assays is due to most of the molecules functioning at a lower rate, rather than a few molecules functioning at the in vivo rate.

Biological Transport, Active↗
PubMed1997

Automated docking of monosaccharide substrates and analogues and methyl alpha-acarviosinide in the glucoamylase active site.

Glucoamylase is an important industrial glucohydrolase with a large specificity range. To investigate its interaction with the monosaccharides D-glucose, D-mannose, and D-galactose and with the substrate analogues 1-deoxynojirimycin, D-glucono-1,5-lactone, and methyl alpha-acarviosinide, MM3(92)-optimized structures were docked into its active site using AutoDock 2.1. The results were compared to structures of glucoamylase complexes obtained by protein crystallography. Charged forms of some substrate analogues were also docked to assess the degree of protonation possessed by glucoamylase inhibitors. Many forms of methyl alpha-acarviosinide were conformationally mapped by using MM3(92), characterizing the conformational pH dependence found for the acarbose family of glucosidase inhibitors. Their significant conformers, representing the most common states of the inhibitor, were used as initial structures for docking. This constitutes a new approach for the exploration of binding modes of carbohydrate chains. Docking results differ slightly from x-ray crystallographic data, the difference being of the order of the crystallographic error. The estimated energetic interactions, even though agreeing in some cases with experimental binding kinetics, are only qualitative due to the large approximations made by AutoDock force field.

1-Deoxynojirimycin↗
PubMed2004

Monosaccharides as silicon chelators: pentacoordinate bis(diolato)(phenyl)silicates with the cis-furanose isomers of common pentoses and hexoses.

Five-coordinate phenylsilicates are formed from the reaction of trimethoxy(phenyl)silane with monosaccharides in methanol in the presence of a stoichiometric amount of base. Five complexes have been isolated and characterized with two ketoses and three aldopentoses. The silicon central atom in [K([18]crown-6)][PhSi(beta-D-Fruf 2,3H-2)2].MeOH (1, Fru=fructose) is part of two chelate rings, with the ligands being beta-D-fructofuranose-O2,O3 dianions. The beta-furanose isomer is best suited for silicon ligation because it exhibits a torsion angle close to 0 degrees for the most acidic diol function, thus assuring a flat chelate ring. The same structural principles are also found in [K([18]crown-6)][PhSi(beta-D-Araf1,2H-2)2].2 MeOH (2, Ara=arabinose), [K([18]crown-6)][PhSi(alpha-D-Ribf1,2H-2)2] (3, Rib=ribose), [K([18]crown-6)][PhSi(alpha-D-Xylf1,2H-2)2]. acetone (4, Xyl=xylose), and [K([18]crown-6)][PhSi(alpha-D-Rulf2,3H-2)2] (5, Rul=ribulose).

Chelating Agents↗
PubMed1990

Thin-layer electrophoretic separation of monosaccharides, oligosaccharides and related compounds on reverse phase silica gel.

The electrophoretic mobilities of monosaccharides, oligosaccharides, sugar alcohols and sugar acids were determined in 0.3 M borate buffer, pH 10, using thin-layer electrophoresis on silanized silica gel, pretreated with octanol-1. A rapid separation of a number of sugars, occurring in foods, could be achieved. Using a 0.05-0.1 M neutral solution of barium acetate as electrolyte, thin-layer electrophoresis allowed excellent and rapid separation as well as identification of all common uronic acids which are constituents of many acidic polysaccharides.

Electrophoresis↗
PubMed1994

Capillary zone electrophoresis of derivatized acidic monosaccharides.

A new and specific precolumn derivatization reaction for acidic monosaccharides was introduced and evaluated in the separation and sensitive detection of carbohydrates by capillary electrophoresis. The derivatization reaction involved the attachment of sulfanilic acid (a UV absorbing tag) or 7-amino-naphthalene-1,3-disulfonic acid (a UV absorbing and fluorescing tag) via a condensation reaction between the amino group of the derivatizing agent and the carboxyl group of the sugar in the presence of a water-soluble carbodiimide. The derivatization reaction replaced the weak carboxylic acid of the sugar by a strong sulfonic acid, which is fully ionized at all pH. This allowed the electrophoresis of the sugar derivatives over a wide pH range and permitted the determination of acidic carbohydrates at very low femtomole levels by UV and fluorescence detection.

2-Naphthylamine↗
PubMed2003

High-speed electrophoretic analysis of 1-phenyl-3-methyl-5-pyrazolone derivatives of monosaccharides on a quartz microchip with whole-channel UV detection.

1-Phenyl-3-methyl-5-pyrazolone (PMP) derivatives of monosaccharides were analyzed by electrophoresis on a quartz microchip with whole-channel UV detection. Rapid separation of PMP derivatives of aldopentoses was achieved by plain-zone electrophoresis in a neutral phosphate buffer with the height equivalent to a theoretical plate at the micrometer level. Zone electrophoresis as borate complexes was also successful for the separation of PMP derivatives of a few aldoses, which were separated within 1 min. Separation by microchip electrophoresis was compared to that by capillary electrophoresis, and the difference was discussed in terms of column efficiency and sample column capacity.

Antipyrine↗
PubMed2006

Effect of monosaccharide composition, glycosidic linkage position and anomericity on the electrophoretic mobility of labeled oligosaccharides.

Fluorophore-assisted carbohydrate electrophoresis (FACE) is useful for separation and characterization of oligosaccharides from various sources and for comparing several samples at once. While characterizing fungal surface glycans by FACE we observed that samples and standards of the same mass did not comigrate as expected. Subsequent experiments showed that the samples did not contain contaminating sugars. Therefore, our observation suggested that glycan electrophoretic mobility is affected by factors in addition to molecular mass. This work assesses the contribution of monosaccharide composition, linkage position, and linkage anomericity to glycan mobility. Commercially available (and synthesized when available) bioses of known composition were derivatized with a charged fluorophore, and electrophoretic mobilities compared in a slab gel format. The results indicate that all three parameters mentioned above affect observed migration. Further, no migration patterns emerged to suggest a set of rules for assigning band identity based on mobility alone. These results emphasize the importance of including known, matched, standards to facilitate interpretation of FACE data.

Candida albicans↗
PubMed1986

Monosaccharide composition of lipopolysaccharides from Campylobacter jejuni and Campylobacter coli.

The monosaccharide composition of the LPS from 5 Campylobacter jejuni strains and 7 Campylobacter coli strains has been studied. All LPS's contained KDO, heptose, glucosamine, glucose, and (with one exception) galactose. All C. jejuni and 3 C. coli LPS's contained greater than 1% galactosamine. 3-Amino-3.6-dideoxyglucose was present in all but one C. coli LPS and in only one C. jejuni LPS.

Campylobacter↗