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PubMed1984

Effect of dietary carbohydrate on monosaccharide uptake by mouse small intestine in vitro.

Using intestinal sleeves in vitro, we studied the effect of dietary carbohydrate on active monosaccharide uptake in mice. Dietary carbohydrate did not affect numerous parameters of intestinal structure, such as length, circumference, weight, protein content, villus dimensions and density, and area at the villus level. Mice on a carbohydrate-free diet had active D-glucose uptake relatively independent of position along the small intestine. A carbohydrate-containing diet reversibly and within 1 day stimulated uptake except in the ileum, restoring the proximal-to-distal gradient in glucose uptake normally observed. This stimulation involved a 81-116% increase in the Michaelis- Menton constant Vmax, and also an apparent increase in the Michaelis- Menton constant Km, that may however be an artifact arising from unstirred-layer effects. Active uptake of 3-O-methyl-D-glucose also increased, permeability to glucose remained unchanged, and proline uptake reversibly decreased (probably due to the lower protein content of the carbohydrate-containing diets). The effect of fasting on active monosaccharide uptake seemed largely due to withdrawal of dietary carbohydrate, rather than of calories per se. It is concluded that dietary carbohydrate causes induction of monosaccharide carriers in the intestine, along with its more familiar induction of pancreatic amylase and intestinal disaccharidases. Substrate-dependent carrier induction may be physiologically significant in maintaining the proximal-to-distal gradient of glucose transport. An appendix presents measurements of villus area as a function of position along the intestine.

3-O-Methylglucose↗

PubMed1998

Insulinotropic action of the polyacetate esters of two non-nutrient monosaccharides in normal and diabetic rats.

The polyacetate esters of certain non-nutrient monosaccharides, such as L-glucose and 2-deoxy-D-glucose, were recently reported to display positive insulinotropic action and, hence, proposed as possible tools for stimulation of insulin release in non-insulin-dependent diabetes. In the present study, the secretory response to four carbohydrate esters was compared in islets of both normal and hereditary diabetic Goto-Kakizaki rats. Three major findings are documented. First, in islets exposed to the dimethyl ester of succinic acid (10.0 mmol/l), D-mannoheptulose hexaacetate (1.7 mmol/l) was found to stimulate insulin release in both normal and diabetic rats. Second, relative to the control value recorded in the sole presence of the succinic acid ester, the increments in insulin output evoked by D-mannoheptulose hexaacetate, alpha-L-glucose pentaacetate and beta-D-glucose pentaacetate (all 1.7 mmol/l) were not lower and, on occasion, even higher in diabetic rats than in control animals. Last, the sole exception to such a rule was encountered in islets exposed to beta-L-glucose pentaacetate, in which case the hexose moiety of the ester might mimic the inhibitory effect of alpha-D-glucopyranose upon phosphorylase a-catalyzed glycogenolysis in islets from diabetic rats. These findings reinforce the concept that the insulinotropic action of monosaccharide esters is not solely attributable to the catabolism of their carbohydrate moiety but also to a direct effect of the esters themselves upon a yet unidentified receptor system. They also provide further support to the possible use of the esters of non-nutrient monosaccharides as insulinotropic tools in type-2 diabetes.

Animals↗

PubMedDate not supplied

Biosynthesis of acid mucopolysaccharides by the surviving new born rat skin. II. - Specific labelling of individual monosaccharides from (U14C)-glucose. Metabolic origin of L-iduronic acid.

1)Individual monosaccharides (uronic acids and aminosugars) have been purified following specific hydrolysis of the mucopolysaccharides from new born rat skin (hyaluronic acid, heparin + heparan sulfate, chondroitin sulfate A, B and C), after incubation with [U14C]-glucose under various conditions and for varying incubation periods. The yields and the specificity of the methods used for hydrolysis are discussed. 2) Monosaccharides from hyaluronic acid and the sulfated mucopolysaccharide fraction are labelled at an approximately equal rate. In addition, high rates of labelling of glucosamine isolated from the sulfated fractions confirms the preferential labelling of (heparin + heparan sulfate) demonstrated with the sulfated polymers. 3) In all fractions, aminosugars are considerably less labelled than the corresponding uronic acids, which suggests the existence of endogeneous diluting precursor pools for the former monosaccharides. 4) No drift of radioactivity from D-glucuronate to L-iduronate could be demonstrated in sulfated mucopolysaccharides after inhibition of their biosynthesis by puromycin or diluting the labelled precursor pools. Hence it has not been possible to substantiate on the surviving tissue the C5 epimerization at the polymer level, as previously demonstrated by other authors with subcellular fractions of various origin.

Animals↗

PubMed1977

Monosaccharide transport in protein-depleted vesicles from erythrocyte membranes.

Treatment of human erythrocyte membranes with dilute alkali (pH 11.5) generates sealed, protein-depleted vesicles that can be isolated by density gradient centrifugation. The vesicles are 0.5 to 2.0 micrometers in diameter, and their membranes are predominantly oriented inside-out. The vesicles lack protein bands 1, 2, 5, and 6 (nomenclature of Steck, T.L. (1974) J. Cell Biol. 62, 1-19) of the erythrocyte membrane. L-Sorbose, a substrate of the monosaccharide transport system in erythrocytes, is transported by the vesicles. Based on comparisons between erythrocytes and vesicles with regard to specificity, temparture dependence, and effects of inhibitors, we conclude that sorbose uptake into the vesicles occurs by way of the monosaccharide transport system. The specific activity of the transport system in vesicles, as determined by initial rate measurements of sorbose uptake, averaged 58% of that in erythrocytes. This finding indicates that the major polypeptides of Bands 1, 2, 5, and 6 do not play an obligatory role in monosaccharide transport.

Biological Transport↗

PubMed1996

The sink-specific and stress-regulated Arabidopsis STP4 gene: enhanced expression of a gene encoding a monosaccharide transporter by wounding, elicitors, and pathogen challenge.

A cDNA for the Arabidopsis STP4 gene (for sugar transport protein 4) was isolated, and the properties of the encoded protein were studied in Schizosaccharomyces pombe. The STP4 monosaccharide H+ symporter is composed of 514 amino acids and has a calculated molecular mass of 57.1 kD. RNA gel blot analyses revealed that STP4 is expressed primarily in roots and flowers of Arabidopsis. This was shown in more detail with STP4 promoter-beta-glucuronidase (GUS) plants yielding strong STP4-driven GUS activity in root tips and anthers. Wounding of plants transformed with STP4-GUS constructs resulted in a rapid increase in GUS activity in cells directly adjacent to the lesion. This was confirmed by RNase protection analyses in Arabidopsis wild-type plants showing a strong, wound-induced increase in STP4 mRNA levels. STP4 expression was induced rapidly in suspension-cultured Arabidopsis cells that were treated with the Pseudomonas syringae elicitor or with chitin or in Arabidopsis plants that were exposed to fungal attacks. Our data suggest that the role of STP4 is to catalyze monosaccharide import into classic sinks, such as root tips and anthers, and, most importantly, to meet the increased carbohydrate demand of cells responding to environmental stress.

3-O-Methylglucose↗

PubMedDate not supplied

Separation of reducing monosaccharides by capillary zone electrophoresis.

The separation of reducing monosaccharides derived from glycosidoproteins and glycolipids by capillary zone electrophoresis (CZE) is dependent on the pH and concentration of the borate buffer. Five saccharides were completely separated in a fused silica capillary tube (50 microns i.d., 65 cm) containing 50 mM borate buffer (pH 10.5) as carrier, with high resolution, at an applied potential of 20 kV after the reducing saccharides were derivatized with 1-naphthylamine. On-column UV (254 nm) monitoring allowed quantitation of these saccharides at least in the concentration range of 10-100 mM in reaction solution. This method was applied to the determination of the monosaccharides composition of various carbohydrate materials to demonstrate its usefulness.

Electrophoresis↗

PubMed1996

The influence of buffer composition on separation efficiency and resolution in capillary electrophoresis of 8-aminonaphthalene-1,3,6-trisulfonic acid labeled monosaccharides and complex carbohydrates.

The effect of buffer conditions -- varying in salt type, pH, and concentration -- on the separation of 8-aminonaphthalene-1,3,6-trisulfonic acid (ANTS)-labeled monosaccharides and complex-type carbohydrates was investigated. Different buffer systems for high and low electroosmotic flow conditions were chosen: a phosphate and a citrate background electrolyte, each at pH 2.5, a phosphate buffer, pH 9.0, and a borate buffer at pH 9.5. All buffer systems displayed differences in resolution and selectivity. Phosphate and borate buffer demonstrated the greatest selectivity changes for ANTS-labeled carbohydrates. While separation in the phosphate system relies mainly on differences in the charge-to-mass-ratio, additional selectivity can be achieved with borate complexation of glycoconjugates. The use of borate buffers improved monosaccharide separations whereas complex carbohydrates showed a loss in resolution. The citrate background electrolyte at low pH caused no significant changes in the separation performance. The pH 9.0 phosphate buffer showed a reversed migration order of the ANTS conjugates with a decreased resolution, compared to the pH 2.5 phosphate buffer, due to the strong electroosmotic flow generated under high pH conditions. An ovalbumin-derived oligosaccharide library demonstrates the significance of buffer selectivity for complex carbohydrate separations. The separation in the acidic phosphate and the alkaline borate buffer generates a different pattern and only the combination of both buffer systems allows an appropriate assessment of sample complexity.

Acids↗

PubMed2006

Tandem mass spectra of ammonium adducts of monosaccharides: differentiation of diastereomers.

Tandem mass spectra of ammonium adducts of monosaccharides gave characteristic fragmentation patterns involving elimination of NH3/H2O followed by multiple eliminations of H2O and cross ring cleavages. Tandem mass spectra were examined over a range of collision energies (1-20 eV) on a triple-quadrupole mass spectrometer. The breakdown behavior of the ammonium adducts revealed patterns that could differentiate diastereomers of monosaccharides.

Glucose↗

PubMed1993

Determination of monosaccharides in glycoproteins by reverse-phase high-performance liquid chromatography.

This report examines monosaccharide composition and content using the reverse-phase high-performance liquid chromatographic separation of p-aminobenzoic ethyl ester derivatives of neutral and amino sugars released from glycoproteins. After acid hydrolysis of glycoproteins with 2 M trifluoroacetic acid, sugars are derivatized with p-aminobenzoic ethyl ester (ABEE), which strongly absorbs uv light at 254 nm in the presence of sodium cyanoborohydride. Reverse-phase (RP)-HPLC of the ABEE-sugar derivatives is performed on Pico.Tag column in an isocratic mode. RP-HPLC conditions are optimized by using ternary mixture as a mobile phase and 45 degrees C as a column temperature. This procedure is very useful for the simultaneous analysis of neutral and amino sugars in a single chromatographic step using RP-HPLC without reacetylation of deacetylated amino sugars, which were produced by acid hydrolysis, and additional chromatography to remove side products. Monosaccharide composition and contents determined on glycoproteins by this method were very comparable to those previously obtained by other techniques.

4-Aminobenzoic Acid↗

PubMed1995

Analysis of monosaccharide composition of mucin oligosaccharide alditols by high-performance anion-exchange chromatography.

A simple one-step method for the analysis of monosaccharides including galactosaminitol after acidic hydrolysis is described. The hydrolyzate was re-N-acetylated and analyzed by high-performance anion-exchange chromatography and the sugars were detected by a pulsed amperometric detector. The method was applied on a mixture of neutral oligosaccharides released from mucin glycopeptides of rat small intestine by alkaline borohydride. Sugars were detected down to the nanomole range and the results were compared with monosaccharide compositional analysis performed by gas chromatography of acetylated alditols.

Acetylation↗

PubMed1998

Contribution of component monosaccharides to the coordinates of neutral and sialyl pyridylaminated N-glycans on a two-dimensional sugar map.

High-performance liquid chromatography elution data on an amide-adsorption and a reverse-phase column, expressed in glucose units, of pyridylamino N-glycans have been analyzed with a new approach using multiple regression to obtain parameters for the contribution ascribable to each of 54 monosaccharide units. Our calculation was based on the 417 different N-glycan structures determined empirically. Depending on the increase in the amount of elution data, we got good correlation (r = 0.9998 for amide-silica and r = 0.9974 for octadecylsilica) and agreement between the observed and the calculated N-glycan elution coordinate values which correspond to the sum of the unit contribution of the component monosaccharides. These calculated values of unit contribution are useful in predicting glycan structure from an observed glucose unit on the map as well as to assume a glucose unit from a given structure. As an example of the application of the unit contribution values to the estimate of a sialyl N-glycan structure, the case of trisialyl triantennary N-glycans is described.

Aminopyridines↗

PubMed1999

Quantitative cleavage of the N-glycosidic bond under the normal conditions of methanolysis used for the analysis of glycoprotein monosaccharides.

The most common method used for the liberation of monosaccharides from glycoprotein N-glycans involves anhydrous methanolysis because it liberates almost quantitatively monosaccharides as O-methylglycosides, which are resistant to further degradation. However, it is generally assumed that this method does not cleave quantitatively the N-glycosidic bonds. This paper demonstrates that classical methanolysis conditions quantitatively cleave the N-glycosidic bond (96%), liberating glucosamine (and not its O-methylglycosides) and other minor reaction products which were identified. Because other N-acetyl-d-glucosamine (GlcNAc) residues are quantitatively liberated as the O-methylglycosides of glucosamine, the GlcNAc residue involved in the N-glycosidic bond is separated from the others using gas chromatography of heptafluorobutyrate derivatives.

Chromatography, Gas↗

PubMed1981

Na dependence of monosaccharide absorption in isolated rabbit small intestine, perfused through lumen and vascular bed.

Na dependence of D-glucose and 3-O-methyl-D-glucose absorption was investigated using the isolated rabbit small intestine perfused through the lumen and the vascular bed, thus imitating in vivo conditions. No dependence of monosaccharide transport of luminal Na concentration was demonstrable if the lumen was perfused at low flow rate. Due to Na secretion, however, Na concentration in the lumen bulk phase, initially being zero, was raised to more than 20 mmol/l during the course of the experiments. Na dependence of sugar transport could be shown, however, if (1) Na secretion was decreased (by use of a vascular medium with low Na concentration) or if (2) unstirred layer thickness was reduced (by enhancement of luminal flow rate). Both conditions allowed the Na concentration near the brush border membrane to be controlled. The results provide an experimental explanation for the apparently low degree of Na dependence of monosaccharide absorption under in vivo conditions.

3-O-Methylglucose↗

PubMed1982

Dolichol-bound oligosaccharides and the transfer of distal monosaccharides in the synthesis of glycoproteins by normal and tumor mammary epithelial cells.

The main dolichol diphosphate-bound oligosaccharides present in primary cultures of both normal and tumor mouse mammary epithelial cells had the same size, yielded the same pattern after acetolysis and paper chromatography, had the same number of mannose residues susceptible to alpha-mannosidase degradation, and were composed of the same monosaccharide residues. This is the first demonstration that normal and tumor mammary cells have dolichol diphosphate-bound oligosaccharides with very similar, if not identical, structures. These compounds are intermediates in the synthesis of asparagine-linked oligosaccharides. On the other hand, normal and tumor cells showed differences in the specific activities of the enzymes involved in the transfer of the distal monosaccharides from the sugar nucleotides to glycoproteins. Sialyl- and fucosyltransferases were elevated and galactosyl- and N-acetylglucosaminyltransferases were diminished in mammary tumor cells. The intact tumor cells showed an increased fucosylation of glycoproteins of the asparagine-linkage type.

Animals↗

PubMed1981

Active transport and mediated diffusion of glucose and other monosaccharides in Endomyces magnusii.

After growth on sucrose or glucose, Endomyces magnusii possess a monosaccharide uptake which resembles that of Saccharomyces cerevisiae (a high KT of uptake, preference for alpha-anomers of D-xylose and D-glucose, enhanced uptake during anaerobiosis, attainment of a diffusion equilibrium). The uptake is inhibited by other monosaccharides and especially strongly by D-galactose. In the absence of high concentrations of metabolizable sugars. E. magnusii develops a capacity to accumulate 3-O-methyl-D-glucose and D-xylose against a concentration gradient the new system displaying a high affinity for glucose (KT less than 0.1 mM), repression by glucose, mannose or galactose. Cycloheximide (0.2%) blocks the formation of the active system.

Ascomycota↗

PubMed2004

AtSTP11, a pollen tube-specific monosaccharide transporter in Arabidopsis.

Pollen development, as well as pollen germination and pollen tube growth, requires a highly regulated supply of sugars. In this paper we describe the molecular, kinetic, and physiological characterization of AtSTP11, a new member of the H+/monosaccharide transporter family in Arabidopsis thaliana (L.) Heynh. Heterologous expression in yeast (Saccharomyces cerevisiae) showed that AtSTP11 is a high-affinity (Km = 25 microM), broad-spectrum, and uncoupler-sensitive monosaccharide transporter of the plasma membrane. In reverse transcription-polymerase chain reaction analyses we found that AtSTP11 expression is restricted to flowers. Furthermore, AtSTP11-promoter::GFP plants revealed that AtSTP11 expression is only found in pollen tubes. Using a specific antibody we could also detect the AtSTP11 protein exclusively in pollen tubes but not in other flower tissues or in pollen grains of any developmental stage. These results suggest that the newly identified AtSTP11 transporter plays a role in the supply of monosaccharides to growing pollen tubes.

Amino Acid Sequence↗

PubMed1989

Simultaneous determination of reducing monosaccharides by capillary zone electrophoresis as the borate complexes of N-2-pyridylglycamines.

Reducing monosaccharides were derivatized to N-2-pyridylglycamines and separated as their borate complexes by capillary zone electrophoresis, using a capillary tube (50 microns i.d., 65 cm) of fused silica containing 200 mM borate buffer (pH 10.5) as carrier. The derivatives of 12 saccharides were completely separated in ca. 25 min, with high resolution, at an applied potential of 15 kV. On-column uv monitoring allowed detection of these derivatives at the 10-pmol level, and quantification by the relative peak area method allowed reproducible determination of these saccharides at least in the concentration range of 10-100 mM in reaction solutions. This method was applied to the determination of the monosaccharide compositions of various carbohydrate materials to demonstrate its usefulness.

Aminopyridines↗

PubMed1986

Proton nuclear magnetic resonance studies of soybean lectin-monosaccharide interactions: computer analysis of complex binding behavior.

1H NMR was used to quantify soybean lectin binding to monosaccharides, using presaturation of HOD plus a spin-echo sequence to observe sugar -NHCOCH3 and -OCH3 to below 0.01 mM. Binding is in the very-slow-exchange limit; there is no broadening or shifting and only unbound sugar is observed for pH 5 to 8 and 25 to 75 degrees C. Preliminary results were consistent with those previously reported for methyl 2-acetamido-2-deoxy-alpha-D-galactopyranoside (Me alpha-D-GalNAcp) (K = 3 X 10(4) liters mol-1 with four sites per tetramer). More detailed studies, however, gave concave Scatchard plots for methyl 2-acetamido-2-deoxy-alpha- and beta-D-galactopyranoside, (Me alpha- and Me beta-D-GalNAcp), best fitted using K1 values of (6-12) X 10(4) liters mol-1, K2 values less than or equal to 0.5 X 10(4) liters mol-1, and four sites of each type in D2O or 80% H2O at 25 degrees C and pH 7.2. Data for methyl alpha-D-galactopyranoside were fitted with K = 0.5 X 10(4) liters mol-1 and eight sites of the same K. Monosaccharides may be binding in the recently reported "hydrophobic sites" of soybean lectin. Both methyl 2-acetamido-2-deoxy-beta-D-galactofuranoside (Me beta-D-GalNAcf) and methyl 2-acetamido-2-deoxy-alpha-D-glucopyranoside (Me alpha-D-GlcNAcP) showed some binding by 1H NMR; K's were similar to those for the high-affinity sugars, but the occupancy was much lower. The soybean lectin in this study was saturated in Ca2+ (greater than or equal to 4 mol/tetramer), but low in Mn2+, with Mn2+ plus Mg2+ less than 4. We report new melting points for D-N-acetylgalactosamine, Me alpha-D-GlcNAcp, Me beta-D-GalNAcp, and Me beta-D-GalNAcf, and a fully listed program for fitting curved Scatchard plots using Apple IIc and IIe computers.

Computers↗