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PubMed1990

Carbohydrate content of apolipoprotein B-48 from rat chylomicrons of varying density.

Monosaccharide composition was determined in apolipoprotein B-48 (apoB) of chylomicrons of rat mesenteric lymph. Chylomicrons were separated into three fractions based on density. Triglyceride and apolipoprotein content were determined in each. ApoB was isolated and quantified using precipitation with isopropanol. Chylomicrons were collected in lymph under normal conditions, and with Poloxalene 2930 when chylomicron secretion was inhibited. Most of the triglyceride was carried in the least dense fraction, while the highest apoB content was in the most dense fraction under normal conditions. Mannose and galactosamine contents of apoB were similar in all fractions while contents of both glucosamine and galactose were highest in the least dense fraction. When chylomicron secretion was inhibited by Poloxalene, the amount of triglyceride recovered in the least dense fraction was significantly reduced. Despite the inhibition of lipid transport in the least dense fraction of chylomicrons by Poloxalene, there was little change in apoB recoveries and in the relative content of various monosaccharides in the apoB from each of the three fractions as compared to results obtained during lipid absorption under normal conditions. In conclusion, carbohydrate composition of apoB of chylomicrons is heterogeneous and varies with chylomicron density.

1-Propanol↗
PubMedDate not supplied

Intestinal digestion and absorption of sucrose in experimental diabetes.

Intestinal sucrose hydrolysis and absorption of monosaccharide products was studied in vivo utilizing the segmental perfusion technique in diabetic and control rats. The proximal jejunum was perfused with 20 mM sucrose, 140 mM NaCl and 0.5% PEG with 14C-PEG, as the nonabsorbable marker. Rates of sucrose hydrolysis and adsorption of monosaccharide products (fructose, and glucose) were determined. There were no statistically significant differences between the diabetic and control rats. This indicates that the previously reported increase in sucrase activity in diabetes does not correlate with enhanced rates of sucrose hydrolysis. Several possibilities for the interpretation of these results are discussed.

Animals↗
PubMed2004

The effects of enrofloxacin on decorin and glycosaminoglycans in avian tendon cell cultures.

Tendonitis and tendon rupture have been reported to occur during or following therapy with fluoroquinolone antibiotics. Though the pathogenesis is unknown, several studies suggest that fluoroquinolone antibiotics alter proteoglycan content in soft tissues, including tendons, and thereby alter collagen fibrillogenesis. To better understand the mechanism of action of fluoroquinolones, we studied the effects of enrofloxacin, a widely used fluoroquinolone in veterinary medicine, on avian tendon cell cultures established from gastrocnemius tendons from 18-day-old chicken embryos. We found that cell proliferation was progressively inhibited with increasing concentrations of enrofloxacin. This was accompanied by changes in morphology, extracellular matrix content and collagen fibril formation as detected by electron microscopy. We also observed a 35% decrease in the content of total monosaccharides in enrofloxacin-treated cells. The ratio of individual monosaccharides was also altered in enrofloxacin-treated cells. Enrofloxacin also induced the synthesis of small amounts of keratan sulfate in tendon cells. Moreover we observed enrofloxacin-induced changes in glycosylation of decorin, the most abundant tendon proteoglycan, resulting in the emergence of multiple lower molecular bands that were identifiable as decorin after chondroitinase ABC and N-glycanase treatment of extracts from enrofloxacin-treated cells. Medium conditioned by enrofloxacin-treated cells contained less decorin than did medium conditioned by control cells. We hypothesize that enrofloxacin induces either changes in the number of N-linked oligosaccharides attached to the core protein of decorin or changes in decorin degradation process. In conclusion, our data suggest that enrofloxacin affects cell proliferation and extracellular matrix through changes in glycosylation.

Animals↗
PubMed2001

Ecophysiological Characterization of Rhizosphere Bacterial Communities at Different Root Locations and Plant Developmental Stages of Cucumber Grown on Rockwool.

Bacterial communities from the rhizosphere of cucumber were characterized with respect to growth rates and carbon source utilization, in order to develop a selection strategy for biocontrol agents against Pythium aphanidermatum. Rhizosphere samples were collected from different root regions (root tips, the root base, and the intermediate region where lateral roots emerge) and developmental stages (the seedling, vegetative, and generative stage) from plants cultivated on reused rockwool. By colony counts on 1/10 strength TSA on subsequent days after plating, percentages of fast- and slow-growing isolates (i.e., forming visible colonies within 2 days, or after 3 or more days, respectively) were determined for each rhizosphere sample. At all plant developmental stages, root tips had the highest percentages of fast growing isolates, and root bases the lowest. During plant growth, the relative amounts of slowly growing bacteria increased. Community-level carbon source utilization was determined for the different rhizosphere samples with Biolog GN plates. Principal component analysis showed that rhizosphere samples from different developmental stages and root locations had distinct carbon source utilization patterns. Communities from root tips of seedlings showed the highest utilization of several monosaccharides. Communities from tips and intermediate regions of plants in the vegetative stage utilized relatively many amino acids and several organic acids, and in the generative stage, more di- and polysaccharides were used. Root base samples scored low with respect to carbon source utilization, except for some disaccharides. From the different rhizosphere samples, 826 bacteria, randomly collected from 1/10 strength TSA plates, were screened on the utilization of 9 carbon sources. The 9 selected carbon sources were chosen because they are reported to occur in the rhizosphere, to be used by the zoospores of Pythium in the infection process, or appeared to be discriminant in the analysis of community-level carbon source utilization performed in this study. It appeared that monosaccharides (glucose and fucose), amino acids (alanine and asparagine), and organic acids (galacturonic, succinic, and linoleic acid) were used for growth mainly by bacteria from the root tips, and to a lesser extent from the intermediate region, of young plants. Disaccharides were predominantly utilized by isolates from plants in the vegetative stage. Overall, the results indicated that growth rates and carbon source utilization reflect the adaptation of bacteria to the rhizosphere environment. The possibility of using these characteristics to screen for rhizosphere competent biocontrol agents that compete for substrates with P. aphanidermatum is discussed.

Journal Article↗
PubMed2004

Molecular analysis of the xylFGH operon, coding for xylose ABC transport, in Thermoanaerobacter ethanolicus.

A xylose ABC (ATP-binding cassette) transport operon, xylFGH, was cloned from Thermoanaerobacter ethanolicus, a thermophilic ethanol-producing eubacterium. The cistrons code for a periplasmic D-xylose-binding protein (XylF, partial sequence of 250 amino acids), ATP-binding protein (XylG, 505 amino acids), and integral membrane protein (XylH, 388 amino acids). These results, together with previous work, indicate that duplicate copies of both xylF and xylH are present in the T. ethanolicus chromosome, suggesting ancient gene duplication or lateral gene transfer events. XylG resembles other eubacterial monosaccharide ABC-ATPases in that its two nucleotide-binding domains (NBDs) are highly homologous, yet significantly different with respect to putative catalytic residues. Unlike most other integral membrane ABC transport proteins, XylH apparently contains 11 or 12 transmembrane segments (TMS) and is similar to a small group of ABC permeases that defy the "2 x 6" helix paradigm. This is the first report of a monosaccharide ABC transport operon in a thermophilic anaerobic eubacterium.

ATP-Binding Cassette Transporters↗
PubMed2004

Absence of turnover and futile cycling of sucrose in leaves of Lolium temulentum L.: implications for metabolic compartmentation.

To study the interdependence of sucrose accumulation and its hydrolyzing enzyme, soluble acid invertase (AI; EC 3.2.1.26), in fructan-accumulating temperate grasses and cereals, experiments were performed in which sucrose synthesis was abolished in leaves of Lolium temulentum by four independent inhibitory factors, each having a distinct mechanism of action. Trials in the light with mannose or vanadate and in the dark with anoxia or cyanide showed that previously accumulated sucrose was stable in the tissue over a 5- to 6-h period. Conversely, putatively vacuolar AI activity in tissue homogenates was sufficient to completely convert endogenous sucrose to monosaccharide within the same period. Continuous invertase-mediated breakdown of sucrose was thus not a feature of this tissue. It is concluded that AI and sucrose were not in metabolic contact in vivo, implying differential compartmentation. In darkness, in uninhibited leaves, sucrose concentrations fell linearly with respect to time at a rate of -0.6 mg g(-1) FW h(-1), over a 5- to 6-h period. This value is equivalent to rates of dark respiration measured by gas exchange. Dark-utilisation of sucrose was not accompanied by monosaccharide accumulation in the tissue. The rate of sucrose loss was 3-fold lower than rates of extractable AI activity. Hence, if AI was involved in dark-utilisation, then this implies at least a partial differential localisation of enzyme and substrate. However, the dark-consumption of sucrose was completely abolished by anoxia and by cyanide. It follows that dark-mobilisation (unlike invertase hydrolysis per se) was respiration-dependent and did not result from a simple co-localisation of sucrose and invertase. Taken together, the results show that sucrose and invertase do not share the same metabolic compartment in grass leaves. It is possible that invertase has no role in the mobilisation of stored sucrose in leaves of the fructan-accumulating grasses.

Darkness↗
PubMed2000

Fractionation of carbohydrates in Arabidopsis root cell walls shows that three radial swelling loci are specifically involved in cellulose production.

Three non-allelic radial swelling mutants (rsw1, rsw2 and rsw3) of Arabidopsis thaliana L. Heynh. were shown to be specifically impaired in cellulose production. Fractionation methods that identify, characterise and quantify some of the major cell wall polysaccharides in small quantities of seedlings demonstrated that changes in the production of cellulose are much more pronounced than changes in the production of non-cellulosic polysaccharides. A crude cell wall pellet was sequentially extracted with chloroform methanol (to recover lipids), dimethyl sulphoxide (starch), ammonium oxalate (pectins) and alkali (hemicelluloses). Crystalline cellulose remained insoluble through subsequent treatments with an acetic/nitric acid mixture and with trifluoroacetic acid. Cetyltrimethylammonium bromide precipitation resolved neutral and acidic polymers in the fractions, and precipitation behaviour, monosaccharide composition and glycosidic linkage patterns identified the major polysaccharides. The deduced composition of the walls of wild-type seedlings and the structure and solubility properties of the major polymers were broadly typical of other dicots. The three temperature-sensitive, radial swelling mutants produced less cellulose in their roots than the wild type when grown at their restrictive temperature (31 degrees C). There were no significant differences at 21 degrees C where no radial swelling occurs. The limited changes seen in the monosaccharide compositions, glycosidic linkage patterns and quantities of non-cellulosic polysaccharides support the view that the RSW1, RSW2 and RSW3 genes are specifically involved in cellulose synthesis. Reduced deposition of cellulose was accompanied by increased accumulation of starch.

Arabidopsis↗
PubMed2003

Gustatory perception and metabolic utilization of sugars by Myrmica rubra ant workers.

The suitability of various nectar and honeydew sugars as a food source for the polyphagous ant species M. rubra (L.) was studied. The sugars used included monosaccharides (fructose, glucose, galactose, mannose, rhamnose), disaccharides (sucrose, maltose, trehalose, melibiose, lactose) and trisaccharides (melizitose, raffinose, erlose). Single-sugar solutions were tested on ant workers in a long-term laboratory bioassay in which acceptance of the solutions and ant survival were recorded. The acceptance of the sugars was confirmed in a second bioassay in which feeding time was established. Enzymatic hydrolysis of sucrose, maltose and melibiose was investigated through HPLC analyses of workers fed these disaccharides. Sugar acceptance and feeding time were related to ant survival. Considering the monosaccharide units of which the sugars are composed, fructose seems especially suitable as a short-term energy source, while glucose appears to be used both directly and for storage. The presence of a galactose unit appears to reduce sugar suitability. It is suggested that the workers possess invertase and maltase and to a lesser degree also galactosidase. The gustatory perception is correlated with the profitability of sugars in further metabolic processes.

Animals↗
PubMed2005

Development of an enzymatic assay for the determination of cellulose bioavailability in municipal solid waste.

As there is a constant need to assess the biodegradation potential of refuse disposed of in landfills, we have developed a method to evaluate the biodegradability of cellulosic compounds (cellulose and hemicellulose) in municipal solid waste. This test is based on the quantification of monosaccharides released after the hydrolysis of solid waste samples with an optimised enzyme preparation containing commercially available cellulases and hemicellulases. We show that the amounts of monosaccharides could be related to the biodegradability of the cellulosic material contained in the samples. This enzymatic cellulose degradation test was assayed on 37 samples originating from three Belgian landfills and collected at different depths. As results correlated well with those obtained with a classical biochemical methane potential assay, this new and rapid test is sufficiently reliable to evaluate cellulose bioavailability in waste samples.

Biodegradation, Environmental↗
PubMed1988

Determination of iduronic acid and glucuronic acid in glycosaminoglycans after stoichiometric reduction and depolymerization using high-performance liquid chromatography and ultraviolet detection.

The reduction of uronic acids in glycosaminoglycans (GAGs) prior to depolymerization reactions is one way in which the uronic acid content of polysaccharides can be studied without major losses. The obtained monosaccharides can be recovered from the subsequent depolymerization with a yield better than 95%. Following reduction, depolymerization, and lyophilization, D-glucuronic acid is converted to D-Glc and L-iduronic acid to 1,6-anhydro-idose. Per-O-benzoyl derivatives of these monosaccharides can be separated and detected in nanogram amounts using reversed phase HPLC. A linear detector response was obtained for injections up to 22 nmol (4 micrograms) of Glc and 1,6-anhydro-idose and the detection limit was 5 and 7 pmol, respectively. Reduction, depolymerization, and derivatization with subsequent chromatography of various GAGs can be readily performed in the 1- to 30-micrograms range.

Chromatography, High Pressure Liquid↗
PubMed1989

A simple and rapid microplate assay for glycoprotein-processing glycosidases.

A simple and convenient microplate assay for glycosidases involved in the glycoprotein-processing reactions is described. The assay is based on specific binding of high-mannose-type oligosaccharide substrates to concanavalin A-Sepharose, while monosaccharides liberated by enzymatic hydrolysis do not bind to concanavalin A-Sepharose. By the use of radiolabeled substrates [( 3H]glucose for glucosidases and [3H]mannose for mannosidases), the radioactivity in the liberated monosaccharides can be determined as a measure of the enzymatic activity. This principle was employed earlier for developing assays for glycosidases previously reported (B. Saunier et al. (1982) J. Biol. Chem. 257, 14155-14161; T. Szumilo and A. D. Elbein (1985) Anal. Biochem. 151, 32-40). These authors have reported the separation of substrate from the product by concanavalin A-Sepharose column chromatography. This procedure is handicapped by the fact that it cannot be used for a large number of samples and is time consuming. We have simplified this procedure and adapted it to the use of a microplate (96-well plate). This would help in processing a large number of samples in a short time. In this report we show that the assay is comparable to the column assay previously reported. It is linear with time and enzyme concentration and shows expected kinetics with castanospermine, a known inhibitor of alpha-glucosidase I.

Animals↗
PubMed1991

Fluorometric determination of carbohydrate with 2-aminothiophenol.

The 2-aminothiophenol-based fluorometric assay of Nakano et al. (1973, J. Pharm. Soc. Jpn. 93, 350-353) for monosaccharides has been modified to improve the speed, applicability, and sensitivity of the method. The improved assay is applicable to complex carbohydrates as well as to monosaccharides. Less than 50 ng of carbohydrate in a final volume of 2 ml can be quantitatively measured within 30 min. The assay is reasonably compatible with the presence of a variety of reagents commonly used in aqueous buffer solutions. The assay is especially useful for monitoring column eluents during the purification of small quantities of carbohydrates or their conjugates.

Aniline Compounds↗
PubMed1991

Sugar analysis of glycoproteins and glycolipids after methanolysis by high-performance liquid chromatography with pulsed amperometric detection.

A procedure for the analysis of the monosaccharide composition of glycoproteins and glycolipids by methanolysis and high-performance liquid chromatography with pulsed amperometric detection is described. The advantage over previous methods is the analysis of underivatized methyl glycosides of all glycoconjugate monosaccharides including sialic acid and uronic acid in a single chromatographic step at the subnanomolar level.

Animals↗
PubMed1992

Cryoprotective activity of synthetic glycophospholipids and their interactions with trehalose.

A series of glycophospholipids have been synthesized by conjugating mono-, di- and trisaccharides with dioleoylphosphatidylethanolamine (DOPE) by reductive amination. These synthetic glycophospholipids were incorporated into egg phosphatidylcholine (PC) vesicles and tested for the release of vesicle-entrapped calcein after five cycles of freeze and thaw. N-isomaltotriosyl-DOPE and N-(N-acetylneuramin-lactosyl)-DOPE had approximately equal activity in cryoprotection; whereas N-lactosyl-DOPE and N-galactosyl-DOPE were without effect. However, the cryoprotective effect of trehalose was significantly reduced with the incorporation of N-lactosyl-DOPE and N-galactosyl-DOPE, but not with the trisaccharide-DOPE conjugates. FTIR studies of mixtures of trehalose and glycophospholipid revealed that trehalose forms H-bonding with the phosphodiester group of N-(N-acetylneuramin-lactosyl)-DOPE but not that of N-galactosyl-DOPE. The presence of interaction of trehalose with the trisaccharide-DOPE conjugate and the absence of interaction with the monosaccharide-DOPE conjugate were also demonstrated by the change of the HII phase transition temperature of dielaidoyl phosphatidylethanolamine as measured by the differential scanning calorimetry. The ability of trehalose to restore the membrane order of the rigid dipalmitoyl phosphatidylcholine bilayer perturbed by the presence of glycophospholipids is also correlated with the ability of trehalose to interact with trisaccharide-DOPE conjugate but not with the monosaccharide-DOPE conjugate. These observations have shed some light on the mechanism of the cryoprotective activity of the membrane bound carbohydrates.

Calorimetry, Differential Scanning↗
PubMed1976

Further studies on a highly purified glycoprotein from the intimal region of procine aorta.

Highly purified glycoprotein from the intimal region of porcine aorta was isolated with minor modifications of the procedure described previously. The molecular weight of the glycoprotein as determined by sedimentation equilibrium method either in presence of 0.1 M NaCl or 6 M guanidine-HCl containing beta-mercaptoethanol was 72 000. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the native glycoprotein and its S-carboxyamidomethyl derivative at different acrylamide concentrations showed no difference in the molecular weight indicating the absence of subunits. Attempts to determine the identity of the amino-terminal acid by a dansylation technique indicated that the amino group is not free. The carboxy-terminal amino acid was found to be serine after treatment of the glycoprotein with carboxypeptidase A. The glycoprotein did not contain an alkali-labile (O-glycosidic) carbohydrate-protein linkage as tested by the beta-elimination reaction. The release of monosaccharides from the glycoprotein as a function of time was studied employing mild acid hydrolysis (0.5 M HCl, 80 degrees C) and also by the use of neuraminidase, alpha-D-and beta-D-glucosidases and beta-D-N-acetylglucosaminidase. From the observations of the release of monosaccharides and analogy with standard features determined by other investigators on soluble aortic glycoproteins, a prediction has been made as to the general features of the carbohydrate moiety of the glycoprotein.

Amino Acids↗
PubMed1984

Structural analysis of heparin by methylation and g.l.c.-m.s.: preliminary results.

Heparin is a complex mixture of polysaccharides differing in biological activity and structure, and attempts to relate this activity to structure have suffered, owing to a lack of sufficiently sensitive and specific analytical methods. Application of methylation analysis to determination of the structure of heparin is described. Carboxyl-reduced heparin was converted into its pyridinium salt, this was dissolved in Me2SO, and free OH and NH groups were methylated with dimethylsulfinyl anion. Sulfate groups were removed by solvolysis, and after dialysis, the polymer was acetylated and depolymerized by acetolysis. The resulting monosaccharides were converted into alditol acetates, which were separated by capillary, gas-liquid chromatography, and identified by both electron impact and chemical ionization mass spectrometry. Seventeen different monosaccharides were identified in the hydrolyzate. All of the expected internal hexosaminyl and glycosyluronic residues were identified. Although several sugars were identified as nonreducing termini, only a hexosamine 6-sulfate was identified as a reducing-terminus sugar. The results indicate that methylation analysis of heparins and other complex, sulfated glycosaminoglycans is feasible.

Chemical Phenomena↗
PubMed1994

Determination of the concentrations of oligosaccharides, complex type carbohydrates, and glycoproteins using the phenol-sulfuric acid method.

The concentrations of methyl glycosides, oligosaccharides, glycopeptides, and glycoproteins can be accurately determined by using calibration curves composed of the appropriate monosaccharide(s) obtained with a modified version of the colorimetric phenol-sulfuric acid method. Calibration curves of micrograms sugar vs. 490 nm for Man, Glc, or Gal are shown to provide reliable determinations (typically +/- 3-4%) of corresponding methyl glycosides and linear and branched-chain oligosaccharides containing the corresponding reactive hexose residue. For complex oligosaccharides containing a known mixture of reactive hexose units, the appropriate mixture of monosaccharides are shown to provide equally accurate calibration curves for concentration determinations. In the case of the soybean agglutinin, which is a tetramer possessing one Man9 oligomannose-type chain per subunit, the protein concentration was determined from the Man calibration curve which agreed with that obtained from the molar extinction coefficient of the protein.

Carbohydrate Conformation↗
PubMed1995

Circular dichroism of the O-specific polysaccharide of Vibrio cholerae O1 and some related derivatives.

The O-specific polysaccharide (O-SP) of Vibrio cholerae O1 is a homopolymer of alpha-(1 --> 2)-linked 4-amino-4, 6-dideoxy-D-mannopyranose whose amino group is acylated with 3-deoxy-L-glycero-tetronic acid [N-(3-deoxy-L-glycero- tetronyl)-alpha-D-perosamine]. The circular dichroism (CD) of the O-SP as well as of a number of N-acyl (formyl, acetyl, 4-hydroxybutyl, 3-deoxy-L-and D-glycero-tetronyl) derivatives of methyl alpha-glycosides of 4-amino-4,6-dideoxy-D-mannopyranose (methyl alpha-D-perosaminide) has been studied for solutions in water, acetonitrile and 1,1,1-trifluoroethanol. The strong solvent dependence of the sign and intensity of the CD observed for the monosaccharide amides bearing achiral acyl groups is explained by solvent-mediated change of the orientation of the amido group relative to the proximal hydroxyl group at C-3. A change in the population of the nonplanar conformers with a pyramidal arrangement of bonds at the amido nitrogen has also been considered. The effect of solvents upon the CD spectra of compounds bearing chiral N-acyl substituents is less pronounced than that of their counterparts bearing achiral N-acyl substituents. The sign of the CD for the O-SP was found negative in all solvents used. This result is in agreement with the negative sign of the CD of the n --> pi electron transition observed, independent of the solvent, for the monosaccharide derivative containing the L-glycero-3-deoxytetronamido group, and the positive sign found for its D-glycero-counterpart.

Acetonitriles↗