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1.
In this paper the possible involvement of the mannose-receptor on the non-specific recognition and phagocytosis of heat killed yeast cells (Saccharomyces cerevisiae) by gilthead seabream (Sparus aurata L.) head-kidney leucocytes was established by studying the ability of different sugars to inhibit the uptake of the yeast cells by leucocytes. Leucocytes were preincubated for 30min with different concentrations of sugar (alpha-mannan, d-mannose, d-fucose, l-fucose, d-glucose, d-glucosamine and n-acetyl-glucosamine, all of them described as specific ligands of the vertebrate mannose-receptor) and afterwards incubated with FITC-labelled yeast cells for phagocytosis assays. The phagocytic ability (percentage of cells with one or more ingested yeast cells within the total cell population) and capacity (number of ingested yeast cells per cell) of leucocytes was analysed by flow cytometry. The results demonstrate the potential existence of a specific receptor-sugar or receptor-yeast cell binding process, which was saturable, specific and dose-dependent. More specifically, when leucocytes were preincubated with appropriate doses of d-mannose, d- or l-fucose, d-glucose or n-acetyl-glucosamine the phagocytosis of yeast cells by head-kidney leucocytes was partially blocked. Seabream leucocytes were also preincubated with chloroquine, a lysosomotropic drug which downregulates (in a nonspecific manner) the expression of mannose-receptors in mammals, before phagocytosis assays were performed. The results demonstrated that the phagocytosis of yeast was completely blocked by this substance. The overall results seem to corroborate the presence of the mannose-receptor in seabream phagocytes, which is involved in the non-specific binding and phagocytosis of yeast cells by head-kidney leucocytes.  相似文献   

2.
1. Conditions are described for the separation and estimation of the neutral monosaccharides obtained on acidic hydrolysis of human gastric mucopolysaccharides. 2. The technique involves the formation of the trimethylsilyl derivatives of the sugars and the analysis of these by gas-liquid chromatography. 3. The monosaccharides estimated in gastric mucopolysaccharides by this technique were l-fucose, d-mannose, d-galactose and d-glucose. 4. The analytical values for glucose and fucose obtained by this method agreed well with values obtained by the glucose oxidase and thioglycollic acid methods respectively. 5. Evidence is presented which clearly indicates that gas-liquid chromatography is a faster, more sensitive and more convenient technique for the measurement of these compounds than any other in use at present.  相似文献   

3.
The slug, Limax flavus, contains a lectin that appears to be highly specific for sialic acid residues of glycoproteins. The carbohydrates which inhibited the hemagglutinating activity of the slug lectin and the concentration of the carbohydrate which gave a 50% inhibition are as follows: N-acetylneuraminic acid, 0.13 mm; N-glycolylneuraminic acid, 0.90 mm; d-glucosamine, 4.9 mm; d-galactosamine, 7.6 mm; N-acetyl-d-glucosamine, 23 mm; and N-acetyl-d-galactosamine, 24 mm. d-Galactose, d-glucose, d-mannose, α-methyl-d-glucoside, α-methyl-d-mannoside, l-arabinose, d-xylose, l-fucose, d-glucuronic acid, lactose, and sucrose were found to be ineffective as inhibitors of the hemagglutinating activity of the slug lectin. Hemagglutination by slug lectin was strongly inhibited by bovine submaxillary mucin and fetuin but not by sialic acid-free bovine submaxillary mucin or fetuin.  相似文献   

4.
An extracellular polysaccharide was isolated from culture broth of Streptomyces sp. A-1845 by ethanol precipitation, DEAE-Toyopearl column chromatography and gel filtrations in Toyopearl HW75f and HW65s. The purified polysaccharide gave a single peak on Toyopearl HW65s gel filtration. Nitrogen and phosphorus content of the purified preparation were 4 and 2.5%, respectively. It was composed of d-mannose, d-galactose, d-galacturonic acid, d-xylose, d-glucosamine, l-rhamnoe, d-glucose, l-fucose, d-ribose and d-galactosamine in the ratio of 7.6, 4.0, 3.4, 3.1, 2.6, 1.9, 1.7, 1.1, 1.0 and 0.6.  相似文献   

5.
The induction of xylose reductase and xylitol dehydrogenase activities on mixed sugars was investigated in the yeasts Pachysolen tannophilus and Pichia stipitis. Enzyme activities induced on d-xylose served as the controls. In both yeasts, d-glucose, d-mannose, and 2-deoxyglucose inhibited enzyme induction by d-xylose to various degrees. Cellobiose, l-arabinose, and d-galactose were not inhibitory. In liquid batch culture, P. tannophilus utilized d-glucose and d-mannose rapidly and preferentially over d-xylose, while d-galactose consumption was poor and lagged behind that of the pentose sugar. In P. stipitis, all three hexoses were used preferentially over d-xylose. The results showed that the repressibility of xylose reductase and xylitol dehydrogenase may limit the potential of yeast fermentation of pentose sugars in hydrolysates of lignocellulosic substrates.  相似文献   

6.
The mucilage isolated from the seed coat of Hyptis suaveolens contains l-fucose, d-xylose, d-mannose, d-galactose, d-glucose and 4-O-methyl-d-glucuronic acid in the mol ratios 1.0:2.5:1.5:7.0:12.5:1.1. Fractionation of the mucilage with Fehling's solution gave a neutral and an acidic polysaccharide. The neutral polysaccharide appears to be homogeneous and is composed of d-mannose, d-galactose and d-glucose in the mol ratios 1.0:4.5:7.5. The acidic polysaccharide is composed of l-fucose, d-xylose and 4-O-methyl-d-glucuronic acid in the mol ratios 1.0:2.5:1.1. It is homogeneous on gel filtration, DEAE-cellulose chromatography, sedimentation analysis and electrophoresis.  相似文献   

7.
Chemotaxis toward sugars in Escherichia coli   总被引:18,自引:30,他引:18       下载免费PDF全文
Using a quantitative assay for measuring chemotaxis, we tested a variety of sugars and sugar derivatives for their ability to attract Escherichia coli bacteria. The most effective attractants, i.e., those that have thresholds near 10(-5) M or below, are N-acetyl-d-glucosamine, 6-deoxy-d-glucose, d-fructose, d-fucose, 1-d-glycerol-beta-d-galactoside, galactitol, d-galactose, d-glucosamine, d-glucose, alpha-d-glucose-1-phosphate, lactose, maltose, d-mannitol, d-mannose, methyl-beta-d-galactoside, methyl-beta-d-glucoside, d-ribose, d-sorbitol, and trehalose. Lactose, and probably d-glucose-1-phosphate, are attractive only after conversion to the free monosaccharide, while the other attractants do not require breakdown for taxis. Nine different chemoreceptors are involved in detecting these various attractants. They are called the N-acetyl-glucosamine, fructose, galactose, glucose, maltose, mannitol, ribose, sorbitol, and trehalose chemoreceptors; the specificity of each was studied. The chemoreceptors, with the exception of the one for d-glucose, are inducible. The galactose-binding protein serves as the recognition component of the galactose chemoreceptor. E. coli also has osmotically shockable binding activities for maltose and d-ribose, and these appear to serve as the recognition components for the corresponding chemoreceptors.  相似文献   

8.
Specificity of sugar-phospholipid interactions   总被引:1,自引:0,他引:1  
Previous studies by Lefevre et al. (6) have shown that phospholipids stimulate uptake of glucose and other sugars by lipid solvents and enhance transfer of glucose through solvent layers into water. In this paper the specificity of the process for different sugars is investigated by following uptake from thin films of sugars or from glass fiber strips coated with radioactive sugars. Hexoses were taken up slowly to molar ratios of sugar to lipid phosphorus of about 1:1. Pentoses and deoxy sugars were taken up 5–10 times more rapidly to molar ratios of between 1.5 and 2.5:1. Relative rates of formation of the complexes at 25 °C were (d-glucose = 1.0):l-fucose, 9.1; d-ribose, 6.1; d-arabinose, 5.5; l-rhamnose, 3.8; l-arabinose, 3.7; d-xylose, 3.6; d-lyxose, 3.1; 3-O-methyl-d-glucose, 1.52; d-mannose, 1.36; d-galactose, 1.13; sucrose, 0.03; and lactose, 0.015. Radioactive sugars bound to phospholipids exchanged readily with unlabeled sugar in the anhydrous state and the sugars passed slowly into the aqueous phase when the complexes were shaken with water. The relative rates of dissociation (d-glucose = 1.0): l-arabinose, 2.82; d-arabinose, 2.49; l-rhamnose, 2.26; l-fucose, 1.96; d-xylose, 1.65; 3-O-methyl-d-glucose, 0.37; d-galactose, 0.28 were in the same general order as formation, suggesting that a common intermediate may be involved in both processes. In general, sugars with high mutarotation rates reacted most rapidly indicating a possible relationship between the structural features which favor interaction with phospholipids and those which enhance mutarotation.  相似文献   

9.
Barber GA 《Plant physiology》1980,66(2):326-329
An enzyme system from fruits of the flax plant is described that catalyzes the synthesis of the sugar nucleotide guanosine 5'-diphosphate l-fucose from guanosine 5'-diphosphate d-mannose with the intermediate formation of guanosine 5'-diphosphate 4-keto-6-deoxy-d-mannose. Tritium from-[(3)H]H(2)O was incorporated into the l-fucose portion of the sugar nucleotide in the course of the reaction, and tritium at the 3,5-carbons of the d-mannose moiety of GDP-d-mannose was exchanged with protons in the medium. These results support a mechanism of synthesis analogous to that proposed for the formation of l-rhamnose and other 6-deoxy sugars.  相似文献   

10.
Mouse peritoneal exudate macrophages were rendered cytostatic and cytolytic for various mouse tumor cells in vitro by exposure to partially purified lymphokines containing macrophage-activating factor (MAF) at 37 °C for 2 hr. The macrophage activation disappeared completely when either 0.1 Md-mannose or 0.1 M methyl-d-mannoside was present with MAF. On the other hand, neither d-galactose nor d-glucose inhibited the activation, and l-fucose, l-rhamnose, and N-acetyl-d-glucosamine inhibited it only partially. Incubation of either macrophages or MAF with 0.1 Md-mannose for 2 hr had no effect on activation of the macrophages by the MAF. Treatment of the macrophages by α-d-mannosidase rendered them no longer responsive to MAF. Macrophages treated by either neuraminidase or proteolytic enzymes, but not with β-d-galactosidase lost their ability to respond to MAF. Treatment of MAF with α-d-mannosidase did not affect MAF activity. In addition, MAF activity was not reduced by passage through a column of immobilized concanavalin A. In an absorption experiment, the presence of d-mannose was shown to prevent the adsorption of MAF to macrophages, while d-galactose did not. Treatment of macrophages with plant lectins having affinity for d-mannose, sialic acid or l-fucose prevented the adsorption of MAF, but the other lectins did not. Mouse MAF failed to adsorb to guinea pig peritoneal exudate macrophage, which were suggested as having a fucose-containing glycolipid as a lymphokine receptor. Taken together, these results strongly suggest that the receptor for MAF on mouse macrophages may be a glycoprotein containing d-mannose and sialic acid as essential components.  相似文献   

11.
A heteropolysaccharide (PS-I), isolated from the hot aqueous extract of an edible mushroom, Termitomyces striatus, is composed of d-glucose, d-galactose, d-mannose and l-fucose in a molar ratio 2:1:1:1. Structural investigation of the native as well as the Smith-degraded polysaccharide was carried out using methylation analysis, periodate oxidation studies and 1D and 2D NMR spectroscopy, and the repeating unit of the polysaccharide is established as follows: [carbohydrate structure: see text]  相似文献   

12.
The kinetics of uptake, accumulation against a concentration gradient, competitive inhibition and metabolic inhibition suggest that d-glucose enters the daughter sporocysts of Microphallus similis by active transport.Studies of competitive inhibition suggest that galactose, fructose, d-fucose, α-methyl-d-glucoside, d-mannose and 3-O-methylglucose are actively absorbed at the same locus as d-glucose. Glucosamine, d-ribose and l-fucose, however, may be actively transported at a different locus or may be taken up by simple diffusion.Acetate, pyruvate, citrate and succinate are absorbed by simple diffusion.  相似文献   

13.
A radiometric assay has been developed for l-fucose which is capable of measuring quantities of this deoxysugar as low as 25 pmol. The assay couples l-fucose dehydrogenase to l-glutamate dehydrogenase and l-glutamate decarboxylase to yield radioactive CO2 which is collected and counted as a measure of l-fucose content. The assay eliminates high backgrounds observed with fluorescence assays.  相似文献   

14.
A new procedure has been devised for the rapid isolation of yeast hexokinase isoenzymes PI and PII, giving specific activities comparable to those obtained after conventional purification. Hexokinases were bound to d-glucosamine, which had been coupled to CH Sepharose 4B using 6-aminohexanoic acid as a spacer. An ATP/d-glucose/MgCl2 solution was used for elution. After concentration with DEAE-Sephacel, isoenzymes were separated by chromatofocusing. Hexokinase PI gave a single band on polyacrylamide gel electrophoresis, whereas one minor foreign band was seen for hexokinase PII.  相似文献   

15.
Seventeen saccharides were tested for their ability to bind to the trap lectins of three species of nematode-trapping fungi and prevent nematode capture. The lectin of Arthrobotrys conoides was found to be inhibited by alpha-d-glucose/d-mannose and similar saccharides. The lectins of Monacrosporium eudermatum and Monacrosporium rutgeriensis were inhibited by alpha-l-fucose and 2-deoxy-d-glucose, respectively. Human group O(H) erythrocytes agglutinated to traps of M. eudermatum but not A. conoides or M. rutgeriensis. There was no agglutination of group A or B to traps formed by all three fungi. Exposure of the traps to trypsin eliminated the ability to capture nematodes. The presence of d-glucose/d-mannose and l-fucose residues on the nematode cuticle was suggested through the use of commercially prepared lectin-peroxidase conjugates.  相似文献   

16.
Extracellular polysachcarides from bacteria and yeasts isolated from decomposed straw contained various proportions of d-galactose, d-glucose, d-mannose, uronic acid, d-xylose, l-fucose and l-rhamnose. Molecular weights of the polymers determined by viscometry and gel filtration were in the range 40 000–1800 000. All the polysaccharides stabilized aggregates of volcanic ash and most were more effective than the polysaccharide from Lipomyces starkeyi. Effectiveness seemed to be more related to molecular weight than to chemical composition.  相似文献   

17.
The effects of various sugars on the simultaneous release of insulin and accumulation of cyclic AMP were studied in collagenase isolated rat pancreatic islets. d-Glucose stimulated the formation of cyclic AMP at 3 and 60 min of incubation, whether measured by a label incorporation technique, or by the protein kinase binding assay of Gilman. Only d-glucose and d-mannose were able to stimulate insulin release and cyclic [3H]AMP accumulation in the absence of other substrate. d-fructose had a stimulatory effect in the presence of 3.3 mM d-glucose only at a high concentration (38.8 mM), and enhanced the effects of 8.3 mM glucose when added at the concentration of 8.3 mM. d-Galactose was effective only together with 8.3 mM d-glucose. The order of potency of these hexoses, both regarding insulin secretion and cyclic [3H]AMP accumulation, was glucose-mannose-fructose-galactose.l-Glucose and 3-O-methylglucose had no effects at 60 min when incubated together with 8.3 mM d-glucose, whereas at 3 min, 3-O-methylglucose induced a small stimulation of the cyclic [3H]AMP response.d-mannoheptulose and d-glucosamine inhibited the insulin and cyclic [3H]-AMP responses to 27.7 mM glucose. Mannoheptulose suppressed completely the glucose effect on cyclic nucleotide accumulation within 90 s.Although under all incubation conditions, the threshold stimulatory or inhibitory concentration of a given agent was identical for insulin release and cyclic [3H]AMP accumulation, these two variables showed quantitative differences in incubations of 60 min, the magnitude of the changes in insulin secretion being larger than that for the cyclic nucleotide. It is suggested that modulation of islet cyclic AMP level is an important step in the transmission of the effect of various sugars on insulin release; however, glucose and possibly other sugars may also enhance insulin release by additional mechanisms not involving the adenylate cyclase-cyclic AMP system of the β-cell.  相似文献   

18.
A human, alveolar glycoprotein having an apparent mol. wt. of 250 000 gave two major glycopeptide fractions (I and II) by Pronase digestion, followed by gel filtration, DEAE-cellulose column chromatography, paper chromatography, and paper electrophoresis. Glycopeptide I contained d-galactose, d-mannose, 2-acetamido-2-deoxy-d-glucose, and N-acetylneuraminic acid in the molar ratio of 2:3:4:1, whereas these sugars were present in Glycopeptide II in the molar ratio of 2:3:4:2.l-Fucose was present only in Glycopeptide II at a concentration of one l-fucose per three d-mannose residues. In both glycopeptides, 2-acetamido-2-deoxy-d-glucose was linked to an asparagine residue of the peptide chain. Based on the results of alkaline borohydride treatment, periodate oxidation, methlylation analysis, and sequential glycosidase degradation of the glycopeptides, tentative structures are proposed for both glycopeptides.  相似文献   

19.
The active principle of miracle fruit which modifies the taste of sour stimuli into a sweet taste was purified by electrofocusing and its chemical propeorties were determined. The electrofocusing resulted in separation of three species of the active proteins (I, II and III) whose isoelectric points were 9.3, 9.0 and 8.0, respectively. Application of three proteins to polyacrylamide gel electrophoresis gave single bands, respectively. All the proteins had the same molecular weight of 40 000–41 000. Essential difference was not found between amino acid compositions of these proteins. N-terminal amino acid residue of the three proteins was determined to be 16% (w/w) for protein I, 20% (w/w) for protein II and 41% (w/w) for protein III. Eight species of carbohydrates (l-fucose, d-mannose, d-galactose, d-glucose, d-xylose, l-arabinose, l-rhamnose and d-glucosamine) were identified by gas chromatography and amino acid analysis as being carbohydrate components of protein II, which was an abundant component, and their relative contents were determined. 1·10−8 M protein II was sufficient to induce the half-maximal sweet-inducing activity.  相似文献   

20.
High-capacity adsorbents for lectins, including Lotus tetragonolobusl-fucose-binding protein, were readily prepared by conjugation of monosaccharides with commercially available, epoxy-activated Sepharose. Purified, radioiodinated lectins were bound to cells of the mosquito Aedes aegyptii and of human KB tumour. Relative to human KB cells, mosquito cells bound less of lectins specific for the sugars (l-fucose and d-galactose) that are terminal residues in many mammalian glycoproteins, whereas the number of binding sites of lectins specific for core-region sugars (d-mannose and 2-acetamido-2-deoxy-d-glucose) were similar. Neuraminidase, which greatly enhanced binding of peanut agglutinin or soybean agglutinin to human KB cells, had negligible effects on binding of these lectins to mosquito cells. The comparative structures of surface oligosaccharides of mosquito and KB cells are discussed in relation to the lectin-binding studies.  相似文献   

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