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PubMed2005

Characterization of exopolysaccharides produced by cyanobacteria isolated from Polynesian microbial mats.

Six cyanobacterial isolates recovered from Polynesian microbial mats, called "kopara," were cultured using laboratory-closed photobioreactors and were shown to produce exopolymers as released and capsular exopolysaccharides (EPS). These polymers have been chemically characterized using colorimetric and elemental assays, infrared spectrometry, and gas chromatography. Both capsular and released EPS consisted of 7 to 10 different monosaccharides with neutral sugars predominating. Interestingly, four isolates exhibited sulfate contents ranging from 6% to 19%. On the basis of preliminary data, cyanobacteria from this unusual ecosystem appear to be an important source of novel EPS of a great interest in terms of their biological activities.

Bacterial Capsules↗
PubMed2006

Disruption of the ste22 gene encoding a glycosyltransferase and its function in biosynthesis of Ebosin in Streptomyces sp. 139.

Streptomyces sp.139 produces an exopolysaccharide (EPS) designated Ebosin with remarkable anti-rheumatic arthritis activity in vivo. The ste (Streptomyces eps) gene cluster required for Ebosin biosynthesis has been identified. According to similarities with other proteins in the database, ste22 shows high homology with glycosyltransferases originated from different microorganisms. In this study, the ste22 gene was disrupted by double crossover via homologous recombination. The EPS produced by the mutant strain Streptomyces sp.139 (ste22(-)) has a different monosaccharide composition profile in comparison with that of Ebosin. This derivative of Ebosin retained the original antagonistic activity of IL-1R in vitro but lost the bioactivities of anti-inflammation and pain relief in vivo.

Antirheumatic Agents↗
PubMed2003

Functional characterization of the Frt1 sugar transporter and of fructose uptake in Kluyveromyces lactis.

Most yeast hexose transporters studied so far at the molecular level mediate facilitated diffusion of glucose and fructose. Here, we report that a novel Kluyveromyces lactis gene, FRT1, encodes a proton-coupled fructose-uptake transporter. Frt1, when expressed in a Saccharomyces cerevisiae hxt null mutant strain that is unable to take up monosaccharides, restored growth on fructose. Determination of substrate specificities and kinetic parameters revealed Frt1 as a fructose transporter with a K(m) of 0.16+/-0.02 mM. Uptake of fructose was accompanied by an initial alkalization of the medium, indicating a proton-coupled uptake mechanism. Deletion of the FRT1 gene in a K. lactis strain already deleted for its RAG1 and HGT1 hexose transporter genes completely prevented uptake of and growth with fructose but not with glucose. Kinetic parameters of Frt1 in K. lactis, as assessed in a rag1 hgt1 mutant strain, were comparable with those obtained after heterologous expression in S. cerevisiae. Transcription of the FRT1 gene, which was undetectable when cells were grown in ethanol, was induced by various sugars. Our results indicate that, unlike S. cerevisiae, K. lactis exhibits proton symport systems for the uptake of hexoses, in addition to their facilitated diffusion.

Biological Transport↗
PubMed2000

Expression of glucose transporters in lactating human mammary gland epithelial cells.

BACKGROUND: Human milk contains 60-80 g/l lactose and and oligosaccharides. To synthesize this large amount of carbohydrates, the lactating mammary gland has a high demand for precursor molecules. such as glucose and galactose. AIM OF THE STUDY: In the present study we investigated the molecular basis for the uptake of glucose and galactose into the human mammary gland. METHODS: Using RT-PCR, Southern and Western blotting we analyzed the expression of SGLT1 (sodium glucose cotransporter 1) und GLUT1 (sodium independent glucose transporter) in epithelial cells isolated from fresh human milk. RESULTS: Southern blot analysis of the amplicions revealed the expression of SGLT1 mRNA but not of GLUT1 mRNA in milk epithelial cells. Using Western blotting, SGLT1 protein was identified in human milk cells. CONCLUSIONS. Our findings indicate that 1) the cell fraction isolated from fresh human milk is a suitable model for investigating gene expression in the human mammary gland and 2) lactating human mammary gland epithelial cells are supplied with monosaccharides mainly via SGLT1.

Blotting, Southern↗
PubMed2003

Cell differentiation, secondary cell-wall formation and transformation of callus tissue of Pinus radiata D. Don.

Tracheid and sclereid differentiation was induced in callus cultures of Pinus radiata D. Don by culturing on a basal medium containing activated charcoal but no phytohormones; sclereids differentiated in callus derived from xylem strips, but not in callus derived from hypocotyl segments. The tracheids differentiated in hypocotyl-derived callus had helical, scalariform, reticulated or pitted secondary cell-wall patterns, but those differentiated in xylem-derived callus had a reticulate or pitted pattern. The thickened tracheid and sclereid walls contained lignin as indicated by the red colour reaction given with phloroglucinol-HCl. The presence of lignin in the cell walls of differentiated callus was confirmed using pyrolysis gas chromatography-mass spectrometry by the detection of phenylpropanoid components derived from lignin. Lignin was also detected using solid-state (13)C cross-polarisation/magic-angle spinning nuclear magnetic resonance spectroscopy and quantified as thioglycolic acid lignin. Monosaccharide analyses of the cell walls isolated from differentiated and undifferentiated calli showed that the cell walls of the differentiated calli contained higher proportions of glucose and mannose, consistent with the presence of greater proportions of gluco- and/or galactogluco-mannans in the secondary cell walls of the differentiated cells. A protocol for the stable transformation of undifferentiated, xylem-derived cultures was successfully developed. Transgenic cell lines were established following Biolistic particle bombardment with a plasmid containing the coding region of the nptII gene and the coding region of the cad gene from P. radiata. Expression of the nptII gene in transgenic lines was confirmed by an NPTII-enzyme-linked immunosorbent assay. The overexpression of cad in the transgenic lines resulted in a down-regulation of cinnamyl alcohol dehydrogenase (EC 1.1.1.195) expression.

Alcohol Oxidoreductases↗
PubMed2000

Isolation and characterisation of cell wall polysaccharides from cocoa (Theobroma cacao L.) beans.

Cell wall material (CWM) was prepared from sun-dried cocoa (Theobroma cacao L.) bean cotyledons before and after fermentation. The monosaccharide composition of the CWM was identical for unfermented and fermented beans. Polysaccharides of the CWM were solubilised by sequential extraction with 0.05 M trans-1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid (CDTA), 0.05 M Na2CO3, and 1 M, 4 M and 8 M KOH. The non-cellulosic sugar composition for each fraction was similar for unfermented and fermented samples, indicating that fermentation caused no significant modification of the structural features of individual cell wall polysaccharides. Pectic polysaccharides accounted for 60% of the cell wall polysaccharides but only small amounts could be solubilised in solutions of CDTA, Na2CO3, and 1 M and 4 M KOH. The bulk of the pectic polysaccharides were solubilised in 8 M KOH and were characterised by a rhamnogalacturonan backbone heavily substituted with side-chains of 5-linked arabinose and 4-linked galactose. Linkage analysis indicated the presence of additional acidic polysaccharides, including a xylogalacturonan and a glucuronoxylan. Cellulose, xyloglucan and a galactoglucomannan accounted for 28%, 8% and 3% of the cell wall polysaccharides, respectively. It is concluded that the types and structural features of cell wall polysaccharides in cocoa beans resemble those found in the parenchymatous tissue of many fruits and vegetables rather than those reported for many seed storage polysaccharides.

Cacao↗
PubMed1999

Composition of the sugar moiety of Tamm-Horsfall protein in patients with urinary diseases.

The sugar moiety of Tamm-Horsfall protein (THP) is altered by pathological conditions. The aim of this study was to investigate the composition of THP glycans in urinary diseases. THP was isolated from the urine of patients with urinary tract infection (group A), glomerulonephritis or interstitial nephritis (group B), and Bartter's syndrome (BS) (group C). Monosaccharides, N-glycan profile, THP reactivity with specific lectins and some other proteins were analyzed. THP of patients from groups A, B, and C showed lower amounts of N-acetylgalactosamine (P<0.05, P<0.005, and P<0.05, respectively) than controls; this was reflected in lower reactivity with Phaseolus vulgaris lectin (P<0.005, P<0.05, and P<0.005). Reduced amounts of N-acetylglucosamine were noticed in groups A (P<0. 05) and B (P<0.05). In group A lower amounts of galactose and alpha2, 6-linked sialic acid, as determined by reactivity with Datura stramonium lectin (P<0.005) and Sambucus nigra lectin (P<0.005), were observed. In patients with BS there was a shift from tetrasialylated glycans towards less-sialylated chains. We found also that THP of all patients binds more strongly to IgG(1) (P<0.005, for all patient groups). Our results indicate that the urinary diseases examined affect the THP sugar moiety and the binding of THP to IgG(1).

Acetylglucosamine↗
PubMed2006

Alcoholic fermentation of carbon sources in biomass hydrolysates by Saccharomyces cerevisiae: current status.

Fuel ethanol production from plant biomass hydrolysates by Saccharomyces cerevisiae is of great economic and environmental significance. This paper reviews the current status with respect to alcoholic fermentation of the main plant biomass-derived monosaccharides by this yeast. Wild-type S. cerevisiae strains readily ferment glucose, mannose and fructose via the Embden-Meyerhof pathway of glycolysis, while galactose is fermented via the Leloir pathway. Construction of yeast strains that efficiently convert other potentially fermentable substrates in plant biomass hydrolysates into ethanol is a major challenge in metabolic engineering. The most abundant of these compounds is xylose. Recent metabolic and evolutionary engineering studies on S. cerevisiae strains that express a fungal xylose isomerase have enabled the rapid and efficient anaerobic fermentation of this pentose. L: -Arabinose fermentation, based on the expression of a prokaryotic pathway in S. cerevisiae, has also been established, but needs further optimization before it can be considered for industrial implementation. In addition to these already investigated strategies, possible approaches for metabolic engineering of galacturonic acid and rhamnose fermentation by S. cerevisiae are discussed. An emerging and major challenge is to achieve the rapid transition from proof-of-principle experiments under 'academic' conditions (synthetic media, single substrates or simple substrate mixtures, absence of toxic inhibitors) towards efficient conversion of complex industrial substrate mixtures that contain synergistically acting inhibitors.

Biomass↗
PubMed2006

Altered expression and glycosylation of plasma proteins in rheumatoid arthritis.

Altered glycosylation of plasma proteins has been directly implicated in the pathogenesis of rheumatoid arthritis (RA). The present study investigated the changes in the Concanavalin-A (Con-A)-bound plasma proteins in the RA patients in comparison to that of the healthy controls. Two proteins (MW approximately 32 kDa and approximately 62 kDa) showed an alteration in expression while an altered monosaccharide profile (high mannose) was observed in the approximately 62 kDa protein in the samples collected from RA patients. The 2-dimensional polyacrylamide gel electrophoresis analysis of the Con-A-bound plasma samples showed a large number of protein spots, a few of which were differentially expressed in the RA patients. Some unidentified proteins were detected in the RA patients which were absent in the control samples. The present study, therefore, enunciates the role of carbohydrates as well as that of the acute phase response in the disease pathogenesis.

Adult↗
PubMed2006

A possible path to the RNA world: enantioselective and diastereoselective purification of ribose.

A theoretical mechanism resulting in the prebiotic appearance of enantiopure ribose, which would be needed for the origin of RNA and the "RNA world" is proposed. The mechanism simultaneously explains the emergence of biological homochirality and could answer the question of why nucleic acids are based on ribose rather than another sugar. Cleavage of certain non-chiral mineral crystals is known to lead to formation of chiral surfaces. In a chromatography-like process a mixture of racemic carbohydrates originating from the formose reaction is proposed to have been separated on such a chiral surface. Monosaccharides interact with surfaces through their hydroxyl groups, either by hydrogen bond formation or complex formation with metal ions. alpha-Ribopyranose, which has all hydroxyl groups on one side of the ring, is known to interact more strongly than other sugars with surfaces, as corroborated by certain chromatographic and electrophoresis data. A similar scenario leading to enantiopure ribose is separation on a flat, but not necessarily chiral surface in the presence of a strong electric field capable of orienting highly polar derivatives of sugars.

Carbohydrates↗
PubMed2004

Identification and characterization of a novel cassava (Manihot esculenta Crantz) clone with high free sugar content and novel starch.

This study reports the identification of a new class of cassava (Manihot esculenta Crantz) with a storage root showing unusual free sugar accumulation and novel starch. Twenty-seven clones high in free sugar were identified under cultivation in primitive rural community areas in the Amazon. Iodine test and glucose oxidase-peroxidase reagent strips were used, in the field, for identification of starch and glucose, respectively. Five out of these 27 clones of cassava were cultivated at EMBRAPA Genetic Resources and Biotechnology and used for biochemical characterization, starch synthesis enzyme activities and gene expression analysis. Carbohydrates were fractioned into free sugar, polymerized water-soluble and -insoluble alpha-polyglucan. Clones of series CAS36 accumulate over 100 times more free sugar (mainly glucose) than commercial varieties. Monosaccharide composition analysis revealed one clone with distinct water-soluble sugars not present in the commercial cultivar. Structure analysis of the water-soluble and -insoluble alpha-polyglucan revealed the presence of a glycogen-like starch in clone CAS36.1. This clone indicated disruption in the starch synthesis pathway for enzyme activities and protein blot analyses in ADPG-pyrophosphorylase and branching enzyme, and their corresponding protein. Gene expression analysis indicated the lack of transcript for the gene coding for branching enzyme, but not for the gene coding for the ADPG-pyrophosphorylase small subunit. In addition, the pattern of distribution of sugar and starch content showed to be related to tissue age in the storage root.

1,4-alpha-Glucan Branching Enzyme↗
PubMed1987

Assay of reducing sugars in the nanomole range with 2,2'-bicinchoninate.

The photometric assay of reducing sugars with 2,2'-bicinchoninate was improved and its conditions were optimized. Optical density is linear between 1 and 25 nmol sugar/sample, and the assay is not affected by borate, phosphate, or other buffer anions. The molar extinction coefficients produced by the standard procedure with the 12 most common monosaccharides occurring in carbohydrates and conjugated glycocompounds are listed.

Indicators and Reagents↗
PubMed1988

Fast atom bombardment-mass spectrometry of glycosphingolipids extracted from thin-layer chromatography plates.

A method is described for analysis of glycosphingolipids extracted from thin-layer chromatography plates. Mixtures of glycolipids and gangliosides were separated by thin-layer chromatography and the individual bands were eluted, permethylated, and, after purification, analyzed by fast atom bombardment-mass spectrometry. The glycosphingolipids could be characterized from their fast atom bombardment mass spectra in terms of partial monosaccharide sequence, ceramide composition, and molecular weight. The sensitivity of the method allows characterization of 1-5 micrograms of glycosphingolipid.

Animals↗
PubMed1989

High-performance liquid chromatography of reducing carbohydrates as strongly ultraviolet-absorbing and electrochemically sensitive 1-phenyl-3-methyl-5-pyrazolone derivatives.

We found that 1-phenyl-3-methyl-5-pyrazolone reacts with reducing carbohydrates almost quantitatively to yield 2:1 compounds having no stereoisomers, which strongly absorb the uv light at 245 nm and are easily oxidizable on a glassy carbon electrode. Reverse-phase partition chromatography on a column of Capcell Pak C18 with uv or electrochemical detection allowed rapid analysis of aldoses and N-acetylhexosamines with the detection limit of 1 pmol or 100 fmol, respectively. This method proved especially useful for analysis of component monosaccharides of glycorproteins. It was also shown to be valid for separation of reducing oligosaccharides; maltodextrins with a degree of polymerization up to 19 were similarly derivatized and separated on this stationary phase.

Animals↗
PubMed1990

Analysis of inositol by high-performance liquid chromatography.

A high-performance liquid chromatographic (HPLC) method has been developed for identification and quantification of inositol isomers and monosaccharides in inositol-containing glycans. The method, which can determine 10 pmol of inositol, utilizes an Aminex HPX-87C column packed with an 8% crosslinked cation-exchange resin in the calcium form eluted with deionized water at 50 degrees C. NaOH solution is added to the column effluent through a postcolumn tee to increase the pH (pH greater than 11.6) before entering a pulsed amperometric detector which is highly sensitive for polyhydroxylated compounds. Samples in which inositol is linked to sugar through a glycosidic bond are hydrolyzed with 5.5 N trifluoroacetic acid, 100 degrees C, 4 h, and then reduced with NaBH4. Samples in which inositol is linked via a phosphate ester are hydrolyzed with 6 N HCl, 110 degrees C, 24 h. This method has been applied to the analysis of inositol in the hamster prion proteins (PrP) PrP27-30, and PrPSc.

Animals↗
PubMed1992

Multivalent ligand binding by serum mannose-binding protein.

The serum-type mannose-binding protein (MBP) is a defense molecule that has carbohydrate-dependent bactericidal effects. It shares with mammalian and chicken hepatic lectins similarity in the primary structure of the carbohydrate-recognition domain, as well as the ligand-binding mode: a high affinity (KD approximately nM) is generated by clustering of approximately 30 terminal target sugar residues on a macromolecule, such as bovine serum albumin, although the individual monosaccharides have low affinity (KD 0.1-1 mM). On the other hand, MBP does not manifest any significant affinity enhancement toward small, di- and trivalent ligands, in contrast to the hepatic lectins whose affinity toward divalent ligands of comparable structures increased from 100- to 1000-fold. Such differences may be explained on the basis of different subunit organization between the hepatic lectins and MBP.

Acute-Phase Proteins↗
PubMed1981

Interaction of monolayers of concanavalin A with mono- and polysaccharides. A study by means of infrared-attenuated total reflectance spectroscopy.

The effects of pH, Mn2+ and Ca2+ and urea denaturation on the interaction of monolayers of concanavalin A on saline with the polysaccharide dextran B-1355 and the monosaccharides methyl alpha-D-mannopyranoside and D-galactose have been investigated. Infrared absorption spectra of compressed monolayers of the protein and the protein-dextran complex coated on a germanium plate have been obtained by means of attenuated total reflectance spectroscopy. Except in one case of denaturation, the amide I absorption of concanavalin A peaked around 1631 cm-1, indicating a predominance of the beta-pleated sheet conformation, in agreement with its secondary structure in the solution and crystalline phases. The contribution to the absorbance of the concanavalin A-dextran films at 3300 cm-1 due to absorption by the O-H stretching modes of the polysaccharide is a measure of its binding. Increasing the pH from 6.1 to 7.5 appreciably reduced the dextran binding, at pH 9.3 the binding was zero. Adding 1 mM Mn2+ and Ca2+ to the subphase at pH 7.5 restored both the dextran binding and the affinity of concanavalin A for methyl alpha-D-mannopyranoside to that of the native protein at pH 6.1. At this latter pH, the weak binding of dextran to monolayers of demetallized concanavalin A (apo-concanavalin A) was also restored to that for the native molecule by the addition of these divalents. This indicates the requirement of concanavalin A for these ions to maintain the integrity of the saccharide-binding site. The loss of dextran binding with urea denaturation was also observed. These results parallel those for solutions of the protein, indicating the validity of the monolayer system for the study of these interactions.

Calcium↗
PubMed1986

Characteristics of D-galactose transport systems by luminal membrane vesicles from rabbit kidney.

The characteristics of renal transport of D-galactose by luminal membrane vesicles from either whole cortex, pars recta or pars convoluta of rabbit proximal tubule were investigated by a spectrophotometric method using a potential-sensitive carbocyanine dye. Uptake of D-galactose by luminal membrane vesicles prepared from whole cortex was carried out by an Na+-dependent and electrogenic process. Eadie-Hofstee analysis of saturation-kinetic data suggested the presence of multiple transport systems in vesicles from whole cortex for the uptake of D-galactose. Tubular localization of the transport systems was studied by the use of vesicles derived from pars recta and pars convoluta. In pars recta, Na+-dependent transport of D-galactose and D-glucose occurred by means of a high-affinity system (half-saturation: D-galactose, 0.15 +/- 0.02 mM; D-glucose, 0.13 +/- 0.02 mM). These results indicated that the "carrier' responsible for the uptake of these hexoses does not discriminate between the steric position of the C-4 hydroxyl group of these two isomers. This is further confirmed by competition experiments, which showed that D-galactose and D-glucose are taken up by the same and equal affinity transport system by these vesicle preparations. Uptake of D-galactose and D-glucose by luminal membrane vesicles isolated from pars convoluta was mediated by a low-affinity common transport system (half-saturation: D-galactose, 15 +/- 2 mM; D-glucose, 2.5 +/- 0.5 mM). These findings strongly suggested that the "carrier' involved in the transport of monosaccharides in vesicles from pars convoluta is specific for the steric position of the C-4 hydroxyl group of these sugars and presumably interacts only with D-glucose at normal physiological concentration.

Animals↗

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