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PubMed1990

Sugar-mediated induction of Agrobacterium tumefaciens virulence genes: structural specificity and activities of monosaccharides.

The virulence genes of Agrobacterium tumefaciens are induced by specific plant phenolic metabolites and sugars (G. A. Cangelosi, R. G. Ankenbauer, and E. W. Nester, Proc. Natl. Acad. Sci. USA, in press). In this report, monosaccharides, derivatives, and analogs which induce the vir regulon have been identified and the structural requirements for monosaccharide-mediated induction have been determined. Pyranose sugars with equatorial hydroxyls at C-1, C-2, and C-3 displayed strong vir gene-inducing activity; the C-4 hydroxyl could be epimeric and a wide variety of substitutions at C-5 were permissible. The acidic monosaccharide derivatives D-galacturonic acid and D-glucuronic acid were the strongest inducers among the monosaccharides tested. Eight of the 11 inducing compounds are known plant metabolites, and 7 are monomers of major plant cell wall polysaccharides. A role for monosaccharides and plant phenolic compounds as wound-specific plant metabolites which signal the ChvE/VirA/VirG regulatory system is proposed.

Bacterial Proteins↗

PubMed2002

Intestinal permeability and carrier-mediated monosaccharide absorption in preterm neonates during the early postnatal period.

Immaturity of intestinal epithelial barrier function and absorptive capacity may play a role in the pathophysiology of intestinal complications in preterm neonates during the early postnatal period. We determined the intestinal permeability and carrier-mediated absorption of monosaccharides in preterm neonates during the first 2 wk after birth. Fifty-nine preterm neonates born between 25 and 32 wk gestation were included within 24 h of birth. Neonates received exclusively parenteral nutrition during the first 7 d after birth; enteral feeding was initiated at d 8. An intestinal permeability-absorption test was performed at 1, 4, 7, and 14 d after birth. The lactulose-to-rhamnose ratio was determined as a marker of intestinal permeability. Urinary excretion percentages of D-xylose and 3-O-methyl-D-glucose were determined as markers of passive and active carrier-mediated monosaccharide absorption, respectively. Intestinal permeability transiently increased between d 1 and 7 in all neonates (p < 0.05). Carrier-mediated monosaccharide absorption increased between d 1 and 14 in neonates of 28-30 wk (p < 0.05) to the level observed in the neonates of 30-32 wk gestation. In neonates <28 wk, intestinal permeability at d 7 was higher (p < 0.05) and carrier-mediated monosaccharide absorption at d 14 was lower (p < 0.01) as compared with neonates >or=28 wk. The barrier function of the intestinal epithelium transiently decreases during the first week after birth in preterm neonates who are not enterally fed. Diminished barrier function and low monosaccharide absorptive capacity, particularly in neonates <28 wk, may predispose these patients to the development of intestinal complications during the early postnatal period.

Female↗

PubMed1998

[High performance liquid chromatographic analysis of monosaccharide composition in lacquer polysaccharide from sap of lac tree].

This paper reports the separation and determination of monosaccharide composition in lacquer polysaccharide (LPS) by HPLC. The five monosaccharides were analyzed on microBondapak NH2 column (300 mm x 7.8 mm i.d. 10 microns) and refractive index detection. The mobile phase was CH3CN-H2O-CH3OH (70:25:5, V/V) flowing at a rate of 1.6 mL/min. These monosaccharides were identified by their retention times and quantitatively determined by their peak areas. LPS samples were hydrolysed with 2.0 mol/L CF3COOH. The linear correlation coefficients were all over 0.9953. The average recoveries of monosaccharides ranged 98.8%-103.6% and relative standard deviations were below 5%. The method is simple, rapid, precise, and has been used satisfactorilly for analysis of the monosaccharides hydrolyzed from LPS, which were isolated from sap of three kinds of Lac tree (Maoba Damu, Maoba Xiaomu and Jianshi) in Hubei province.

Chromatography, High Pressure Liquid↗

PubMed2003

[Comparison of Echinops species on the basis of the monosaccharide composition of polysaccharides].

The goal of our investigation was to compare the monosaccharide composition of polysaccharides of different Echinops species. The determination of monosaccharid composition was made after Taylor reduction, acidic hydrolysis, reduction with sodium borohydride and acetylation in pyridine/aceticanhydride as alditol-acetates with gas chromatographic analysis. 4-O-methyl-glucuronic acid was found in all studied species. The best similarity was found in the case of the monosaccharide composition of E. ruthenicus and E. exaltatus where rhamnose and arabinose are the main monosaccharides and 4-O-methyl-glucuronic acid is the uronic acid component. The main monosaccharides are glucose in E. orientalis and glucose and mannose in E. commutatus. Glucuronic acid is the uronic acid component in both species.

Asteraceae↗

PubMed1969

Mitochondrial autonomy: incorporation of monosaccharides into glycoprotein by isolated mitochondria.

Isolated intact mitochondria selectively incorporate monosaccharides from nucleotide diphosphate monosaccharides into protein. Fucose, mannose, glucose, and galactose were incorporated by the mitochondria into glycoprotein; xylose was not. Structural integrity of the mitochondria was not necessary for the incorporation of monosaccharide into glycoprotein; mitochondria broken by homogenization also incorporated monosaccharide. The monosaccharides incorporated into glycoprotein were localized in the inner mitochondrial membranes, the same membranes which contain the protein into which leucine is incorporated by the isolated mitochondria.

Animals↗

PubMed2005

VvHT1 encodes a monosaccharide transporter expressed in the conducting complex of the grape berry phloem.

The accumulation of sugars in grape berries requires the co-ordinate expression of sucrose transporters, invertases, and monosaccharide transporters. A monosaccharide transporter homologue (VvHT1, Vitis vinifera hexose transporter 1) has previously been isolated from grape berries at the veraison stage, and its expression was shown to be regulated by sugars and abscisic acid. The present work investigates the function and localization of VvHT1. Heterologous expression in yeast indicates that VvHT1 encodes a monosaccharide transporter with maximal activity at acidic pH (pH 4.5) and high affinity for glucose (K(m)=70 muM). Fructose, mannose, sorbitol, and mannitol are not transported by VvHT1. In situ hybridization shows that VvHT1 transcripts are primarily found in the phloem region of the conducting bundles. Immunofluorescence and immunogold labelling experiments localized VvHT1 in the plasma membrane of the sieve element/companion cell interface and of the flesh cells. The expression and functional properties of VvHT1 suggests that it retrieves the monosaccharides needed to provide the energy necessary for cell division and cell growth at an early stage of berry development.

Base Sequence↗

PubMed2006

Pathways of glucose regulation of monosaccharide transport in grape cells.

Grape (Vitis vinifera) heterotrophic suspension-cultured cells were used as a model system to study glucose (Glc) transport and its regulation. Cells transported D-[14C]Glc according to simple Michaelis-Menten kinetics superimposed on first-order kinetics. The saturating component is a high-affinity, broad-specificity H+ -dependent transport system (Km = 0.05 mm). Glc concentration in the medium tightly regulated the transcription of VvHT1 (Vitis vinifera hexose transporter 1), a monosaccharide transporter previously characterized in grape berry, as well as VvHT1 protein amount and monosaccharide transport activity. All the remaining putative monosaccharide transporters identified so far in grape were poorly expressed and responded weakly to Glc. VvHT1 transcription was strongly repressed by Glc and 2-deoxy-D-Glc, but not by 3-O-methyl-D-Glc or Glc plus mannoheptulose, indicating the involvement of a hexokinase-dependent repression. 3-O-Methyl-D-Glc, which cannot be phosphorylated, and Glc plus mannoheptulose induced a decrease of transport activity caused by the reduction of VvHT1 protein in the plasma membrane without affecting VvHT1 transcript levels. This demonstrates hexokinase-independent posttranscriptional regulation. High Glc down-regulated VvHT1 transcription and Glc uptake, whereas low Glc increased those parameters. Present data provide an example showing control of plant sugar transporters by their own substrate both at transcriptional and posttranscriptional levels. VvHT1 protein has an important role in the massive import of monosaccharides into mesocarp cells of young grape berries because it was localized in plasma membranes of the early developing fruit. Protein amount decreased abruptly throughout fruit development as sugar content increases, consistent with the regulating role of Glc on VvHT1 expression found in suspension-cultured cells.

Biological Transport↗

PubMed2006

Molecular identification and physiological characterization of a novel monosaccharide transporter from Arabidopsis involved in vacuolar sugar transport.

The tonoplast monosaccharide transporter (TMT) family comprises three isoforms in Arabidopsis thaliana, and TMT-green fluorescent protein fusion proteins are targeted to the vacuolar membrane. TMT promoter-beta-glucuronidase plants revealed that the TONOPLAST MONOSACCHARIDE TRANSPORTER1 (TMT1) and TMT2 genes exhibit a tissue- and cell type-specific expression pattern, whereas TMT3 is only weakly expressed. TMT1 and TMT2 expression is induced by drought, salt, and cold treatments and by sugar. During cold adaptation, tmt knockout lines accumulated less glucose and fructose compared with wild-type plants, whereas no differences were observed for sucrose. Cold adaptation of wild-type plants substantially promoted glucose uptake into isolated leaf mesophyll vacuoles. Glucose uptake into isolated vacuoles was inhibited by NH(4)(+), fructose, and phlorizin, indicating that transport is energy-dependent and that both glucose and fructose were taken up by the same carrier. Glucose import into vacuoles from two cold-induced tmt1 knockout lines or from triple knockout plants was substantially lower than into corresponding wild-type vacuoles. Monosaccharide feeding into leaf discs revealed the strongest response to sugar in tmt1 knockout lines compared with wild-type plants, suggesting that TMT1 is required for cytosolic glucose homeostasis. Our results indicate that TMT1 is involved in vacuolar monosaccharide transport and plays a major role during stress responses.

Amino Acid Sequence↗

PubMed2001

Gas chromatography/combustion/isotope-ratio-monitoring mass spectrometric analysis of methylboronic derivatives of monosaccharides: a new method for determining natural 13C abundances of carbohydrates.

Monosaccharides were derivatized using methylboronic acid and N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA), and the delta13C values of these derivatives measured by gas chromatography/combustion/isotope-ratio-monitoring mass spectrometry to determine the original 13C-content of the monosaccharides. Comparison with the measured off-line delta13 values of the monosaccharides shows that no fractionation in 13C takes place during derivatization. The methylboronic derivatization method has proven to be a new method for natural abundance isotopic analysis of intact monosaccharides (arabinose, xylose, fucose, fructose and glucose). The method is rapid, does not involve isotopic fractionation during derivatization, and gives more precise delta13C values than other methods reported. The method was successfully applied to determine the delta13C value of glucose of the freshwater alga Scenedesmus communis.

Arabinose↗

PubMed2007

The distinction of underivatized monosaccharides using electrospray ionization ion trap mass spectrometry.

A convenient method for distinguishing underivatized isomeric monosaccharides has been established using electrospray ionization ion trap mass spectrometry (ESI-ITMS). Mass spectra of hexoses (glucose, galactose, and mannose), N-acetylhexosamines (N-acetylglucosamine, N-acetylgalactosamine, and N-acetylmannosamine) and hexosamines (glucosamine, galactosamine, and mannosamine) dissolved in solvent containing 1 mM ammonium acetate were obtained in the positive ion mode. Glucose was distinguished from galactose and mannose in the MS(2) spectrum of the [M+NH(4)](+) ion at m/z 198. The MS(3) spectra generated from [M+NH(4)-H(2)O-NH(3)](+) at m/z 163 showed that galactose and mannose could be distinguished by the ratio of peak intensities at m/z 145 and 127, while the three N-acetylhexosamine and hexosamine stereochemical isomers could be identified by the relative abundance ratios of product ions observed in MS(3) spectra. The investigation of MS and MS(2) spectra from complexes of these monosaccharides with Na(+) and Pb(2+) failed to distinguish these monosaccharide isomers. Therefore, multiple stage mass analysis by ESI-ITMS using either [M+NH(4)](+) or [M+H](+) was useful to distinguish between the isomers of monosaccharides.

Isomerism↗

PubMed1988

Monosaccharide analysis of glycoconjugates by anion exchange chromatography with pulsed amperometric detection.

The method of anion exchange chromatography followed by pulsed amperometric detection (AE-PAD; Johnson, D. C., and Polta, T. Z. (1986) Chromatogr. Forum 1, 37-44) has been applied to the compositional analysis of glycoconjugates. Using 22 mM NaOH as a column effluent, underivatized fucose, galactosamine, glucosamine, galactose, glucose, and mannose were readily separated in 15 min at a flow rate of 1 ml/min. The limit of quantification of the monosaccharides was better than 100 pmol (signal to noise ratio 184:1). AE-PAD was employed to quantify the monosaccharides of several glycoproteins, glycopeptides, and oligosaccharides after hydrolysis with 2 M trifluoroacetic acid. Both neutral and amino sugars could be rapidly estimated in a single chromatographic step using AE-PAD. Complete release of N-acetylglucosamine required more vigorous hydrolysis conditions (Lee, Y. C. (1972) in Methods in Enzymology (Ginsburg, V., Ed.), Vol. 28, pp. 63-73, Academic Press, New York). In both glycopeptides and oligosaccharides, approximately one less residue of Man than predicted was determined. Both AE-PAD and liquid chromatographic analysis of borate-monosaccharide complexes with fluorometric detection (Mikami, H., and Ishida, Y. (1983) Bunseki Kagaku 32, E207-E210) gave similar quantification of mannose and other sugars. The capability of rapid, sensitive quantification of underivitized monosaccharides should facilitate structural analysis of glycoconjugates.

Amino Sugars↗

PubMed1992

Structure-retention index relationships for derivatized monosaccharides on non-polar gas chromatography columns.

A gas chromatographic method for predicting the retention index of a derivatized monosaccharide is presented. The procedures are especially useful to detect and predict minute quantities of sugars in biological or chemical samples. Monosaccharides are first converted to the alditols and then derivatized by acetylation, permethylation or silylation. The derivatized monosaccharide structure-retention index relationship that has been developed is useful in the identification of unknown monosaccharides that can be readily confirmed by gas chromatography-mass spectrometry.

Acetylation↗

PubMed1989

Age influence on sucrose hydrolysis and on monosaccharide absorption along the small intestine of rat.

The consequences of aging on the hydrolysis and absorption of hexoses was assessed in vitro using everted intestinal segments. Glucose and fructose were given either as a mixture of free monosaccharides or as a disaccharide solution (sucrose). The jejuno-ileum of 3- and 24-month-old rats was everted and divided into four equal segments. For each segment, the mucosal medium contained either sucrose (140 mM) or an equimolar mixture of glucose and fructose (70 mM). Monosaccharide concentrations in the mucosal ans serosal media were measured after 1 h of incubation at 37 degrees C. In the young adult, glucose absorption was enhanced when given as sucrose. In contrast, in the aged rat, free glucose or glucose released from sucrose hydrolysis were similarly absorbed. Independently of age, fructose was better absorbed when provided in a mixture of free monosaccharides. The intestinal segments (and especially the ileum), of the aged animals exhibited higher abilities to hydrolyse sucrose and to absorb monosaccharides indicating a normal or increased intestinal hydrolytic activity and absorptive capacity for dietary sugars.

Aging↗

PubMed1984

The autoxidation of glyceraldehyde and other simple monosaccharides under physiological conditions catalysed by buffer ions.

Glyceraldehyde and other simple monosaccharides autoxidise under physiological conditions generating 1-hydroxyalkyl (carbon-centred) free radicals and intermediates of dioxygen reduction: superoxide, hydrogen peroxide and hydroxyl radicals. The major glyceraldehyde-derived product is the alpha-ketoaldehyde, hydroxypyruvaldehyde. Close similarities between the temperature dependence of the kinetics of glyceraldehyde autoxidation and glyceraldehyde enolisation to an ene-diol indicates that enolisation is the rate-determining step in the autoxidative process. Inspection of a wide range of carbonyl compounds showed that the monosaccharide moiety -CH(OH)-C- is conserved in carbonyl compounds reactive towards autoxidation, indicating that the ability to form an ene-diol is a prerequisite to monosaccharide autoxidation. The ene-diol intermediate autoxidises rapidly to the products: hydrogen peroxide, water and alpha-ketoaldehydes: beta-hydroxypyruvaldehyde is produced from glyceraldehyde and dihydroxyacetone, glyoxal from glycolaldehyde autoxidation. Ene-diol autoxidation is catalysed by hydrogen peroxide and trace metal ion contaminants; removal of either of these factors sufficiently retards ene-diol autoxidation such that ene-diol autoxidation rather than enolisation becomes the rate determining step in the overall autoxidative process. Under enolisation control, the rate of monosaccharide autoxidation is influenced by pH and the buffer system used for pH control.

Animals↗

PubMed2006

Monosaccharide-H2O2 reactions as a source of glycolate and their stimulation by hydroxyl radicals.

An analysis of the H(2)O(2)-induced breakdown and transformation of different keto-monosaccharides at physiological concentrations reveals that glycolate and other short-chained carbohydrates and organic acids are produced. Depletion of monosaccharides and glycolate synthesis occurs at increased rates as the length of the carbohydrate chain is decreased, and is significantly increased in the presence of trace amounts of Fe(2+) ions (10 microM). Rates of monosaccharide depletion (initial concentration of 3 mM) observed were up to 1.55 mmol h(-1) in the case of fructose, and 2.59 mmol h(-1) in the case of dihydroxyacetone, depending upon pH, H(2)O(2) concentration, temperature and the presence or absence of catalytic amounts of Fe(2+). Glycolate was produced by dihydroxyacetone cleavage at rates up to 0.45 mmol h(-1) in the absence, and up to 1.88 mmol h(-1) in the presence of Fe(2+) ions (pH 8). Besides glycolate, other sugars (ribose, glyceraldehyde, glucose), glucitol (sorbitol) and organic acids (formic and 2-oxogluconic acid) were produced in such H(2)O(2)-induced reactions with fructose or dihydroxyacetone. EPR measurements demonstrated the participation of the OH radical, especially at higher pH. Presence of metal ions at higher pH values, resulting in increased glycolate synthesis, was accompanied by enhanced hydroxyl radical generation. Observed changes in intensity of DEPMPO-OH signals recorded from dihydroxyacetone and fructose reactions demonstrate a strong correlation with changes in glycolate yield, suggesting that OH radical formation enhances glycolate synthesis. The results presented suggest that different mechanisms are responsible for the cleavage or other reactions (isomerisation, auto- or free-radical-mediated oxidation) of keto-monosaccharides depending of experimental conditions.

Chelating Agents↗

PubMed2002

Formation of a self-assembled phenylboronic acid monolayer and its application toward developing a surface plasmon resonance-based monosaccharide sensor.

For the surface-optoelectronic study of sugar sensing, we synthesized and characterized dithiobis(4-butyrylamino-m-phenylboronic acid) (DTBA-PBA) as a recognition molecule. DTBA-PBA has a boronic acid group that has been known to form covalently bonded complexes with the 1,2- or 1,3-diol of sugars. A self-assembled monolayer (SAM) of DTBA-PBA was formed on a gold surface and characterized by atomic-force microscopy, Fourier transform infrared reflection absorption spectroscopy, and surface electrochemical measurements. An interaction study between monosaccharides and DTBA-PBA SAM was performed using surface plasmon resonance spectroscopy. The increase in molecular interactions between DTBA-PBA SAM and monosaccharides resulted in an optically induced electron excitation change on the Au surface through a refractive index change of the interfacial recognition layer. This correlation between electron excitation and molecular interaction was measurable at very low monosaccharide concentrations (1.0 x 10(-12)M). DTBA-PBA SAM shows a selective fructose sensing among four kinds of monosaccharides, even in a low concentration range.

Biosensing Techniques↗

PubMed2000

Effect of stereochemistry on the anti-freeze characteristics of carbohydrates. A thermal study of aqueous monosaccharides at subzero temperatures.

Thermal behavior at subzero temperatures has been investigated for aqueous solutions of various monosaccharides. The heat of fusion of ice measured with differential scanning calorimetry has given linear plots against sugar concentration (wt.%), from which the amount of unfrozen water, Uw, has been determined for each monosaccharide. The results for Uw are analyzed by employing, as a measure of hydration characteristics, known physico-chemical properties of aqueous monosaccharides, such as partial molar compressibilities, etc. It was revealed that the anti-freeze characteristics of carbohydrates depend on their stereochemistry. More water remains unfrozen in the aqueous solutions of carbohydrates having poorer compatibility with the three-dimensional hydrogen-bond network of water. Monosaccharides studied can be subdivided into three groups according to the extent of the anti-freeze effect. These results are rationalized in terms of a modified stereospecific hydration model.

Calorimetry, Differential Scanning↗

PubMed1997

Analysis of monosaccharide composition by capillary electrophoresis.

The monosaccharide composition analysis described in this paper employs capillary electrophoretic separation of sugar monomers liberated from glycoproteins or oligosaccharides, by high temperature acidic hydrolysis. Trifluoroacetic acid was used for sialo- and neutral-sugar hydrolysis, and hydrochloric acid was used for amino-sugar hydrolysis. The neutral- and amino-sugars in the hydrolyzates were then labeled with a charged fluorophore, 8-aminopyrene-1,3,6-trisulfonate, while sialic acids were labeled with 9-aminoacridone. The stoichiometry of labeling was such that only one fluorophore molecule was attached to each monosaccharide molecule. The labeled monosaccharides were then separated by high-performance capillary electrophoresis with laser induced fluorescence detection. The acidic hydrolysis and fluorophore labeling conditions described in this paper are suitable for monosaccharide composition analysis of a wide variety of complex carbohydrates from glycoprotein and/or oligosaccharide samples using capillary electrophoresis.

Acetylglucosamine↗