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Structural study of the sugar chains of CD36 purified from bovine mammary epithelial cells: occurrence of novel hybrid-type sugar chains containing the Neu5Ac alpha 2-->6GalNAc beta 1-->4GlcNAc and the Man alpha 1-->2Man alpha 1-->3Man alpha 1-->6Man groups.

CD36 is a glycoprotein included in the bovine milk fat globule membrane derived from mammary secretory epithelial cells during lactation. Asparagine-linked sugar chains were quantitatively released from CD36 as oligosaccharides by hydrazinolysis. These sugar chains were converted to radioactive oligosaccharides by reduction with NaB3H4 and separated into neutral and acidic fractions by paper electrophoresis. Most of the acidic oligosaccharides were converted to neutral ones by sialidase digestion, indicating that they are sialyl derivatives. The neutral and sialidase-treated acidic oligosaccharides were fractionated by Bio-Gel P-4 column chromatography in combination with serial chromatography on immobilized lectin columns including a Wistaria floribunda agglutinin (WFA)-agarose column. WFA is known to bind oligosaccharides terminating with either an alpha- or beta-N-acetylgalactosamine residue. Structural studies of oligosaccharides in each fraction by sequential exoglycosidase digestion as well as methylation analysis revealed that CD36 contains high mannose-type, hybrid-type, and bi, tri-, and tetraantennary complex-type sugar chains. A portion of the hybrid-type and the complex-type sugar chains which bound to a WFA-agarose column (28% of all oligosaccharides) contained the GalNAc beta 1-->4GlcNAc group(s) instead of the Gal beta 1-->4GlcNAc group(s) in their outer chain moieties. Like oligosaccharides found in human luteinizing hormone [Weisshaar, G., Hiyama, J., Renwick, A. G., & Nimtz, M. (1991) Eur. J. Biochem. 195, 257-268], some of the GalNAc beta 1-->4GlcNAc groups found in the CD36 oligosaccharides were sialylated as the Neu5Ac alpha 2-->6GalNAc group. Furthermore, most of the hybrid-type sugar chains of CD36 with the Gal/GalNAc beta 1-->4GlcNAc beta 1-->2 outer chain on their Man alpha 1-->3 arm contained an unusual Man alpha 1-->2Man alpha 1-->3 group on their Man alpha 1-->6 arm.

Animals↗

Manufacture of fermentable sugar solutions from sugar cane bagasse hydrolyzed with phosphoric acid at atmospheric pressure.

Sugar cane bagasse, a renewable and cheap bioresource, was hydrolyzed at 100 degrees C using phosphoric acid at different concentrations (2, 4, or 6%) and reaction times (0-300 min) to obtain fermentable sugar solutions, which have a high concentration of sugars (carbon source for microorganism growth) and a low concentration of growth inhibitors (acetic acid and furfural). Xylose, glucose, arabinose, acetic acid, and furfural were determined following the hydrolysis. Kinetic parameters of mathematical models for predicting these compounds in the hydrolysates were obtained. Derived parameters such as efficiency of hydrolysis or purity of hydrolysates were considered to select as optimal conditions 6% phosphoric acid at 100 degrees C for 300 min. Using these conditions, 21.4 g of sugars L(-)(1) and <4 g of inhibitors L(-)(1) were obtained from the hydrolysis with a water/solid ratio of 8 g of water g(-)(1) of sugar cane bagasse on a dry basis.

Atmospheric Pressure↗

A novel sugar-stimulated covalent switch in a sugar sensor.

The bgl sensory system is composed of a membrane-bound sugar sensor, BglF, and a transcriptional regulator, BglG. The sensor BglF has several enzymatic activities: in its nonstimulated state, it acts as BglG phosphorylase; in the presence of beta-glucoside in the growth medium, it acts as BglG dephosphorylase and as the beta-glucoside phosphotransferase. The same active site on BglF, Cys-24, is responsible for the phosphorylation of both the stimulating sugar and the BglG protein. BglF is composed of three domains, two hydrophilic and one hydrophobic. Our previous results suggested that catalysis of the sugar-stimulated functions depends on specific interactions between the B domain, which contains the active site cysteine, and the integral membrane C domain. We report here that the stimulating sugar triggers the formation of a disulfide bond between the active site cysteine and another cysteine in the membrane-embedded domain of BglF. Inability of a mutant BglF protein to form the disulfide bridge between the B and C domains correlates with its inability to catalyze the sugar-stimulated functions. The ability of the cysteine residue in BglF to bind covalently either to a phosphoryl group or to another cysteine residue, depending on the protein stimulation state, suggests a novel way to control signaling by alternative bond formation.

Bacterial Proteins↗

A comparative study of the effects of white sugar, unrefined sugar and starch on the efficiency of food utilization and thermogenesis.

Energy balance studies with weanling rats and mice were carried out to investigate the chronic effects of diets containing white sugar, unrefined sugar, and starch as sole carbohydrate on body composition and energetic efficiency. The results show no significant differences in energetic efficiency and in body composition of both rats and mice fed the different carbohydrate diets. However, there is a tendency for the sugar-fed animals to have higher metabolizable energy intakes, but rarely was this sufficient to increase body energy since there were corresponding increases in metabolic rate. These studies indicate that differences in energy balance between sugar and starch are small and that any increase in thermogenesis that occurred in some of the groups fed sugar-rich diets was in response to the higher energy intake rather than due to a lower efficiency of utilization of sucrose per se.

Animals↗

Blood sugar levels and renal sugar excretion after the intake of high carbohydrate diets in cats.

The effect of starch and sugars on blood sugar level and renal excretion of sugars and galactitol was investigated. Fifty-nine adult cats were divided into seven dietary groups (carbohydrate content in dry matter): STARCH (29-37% starch, decomposed or raw), SUC (36% sucrose), LAC1 and LAC2 (11 and 28% lactose, respectively), GLUC (40% glucose), GAL (39% galactose) and a carbohydrate-free control diet, FAT. Diet STARCH did not significantly influence postprandial blood glucose level (3.65 +/- 0.68 mmol/l +/- SD, n = 16) compared with diet FAT (3.20 +/- 0.77 mmol/l, n = 14) 1, 3 or 6 h after feeding (weighted means). Diet GLUC led to a steep rise in blood glucose concentration 1 h after feeding (5.08 +/- 0.69 mmol/l, n = 6). Diet SUC induced a mild persistent hyperglycemia without marked postprandial changes (4.52 +/- 0.52 mmol/l, n = 15, weighted mean of 0, 3 and 6 h post-prandially). Diet GAL induced persistent hypoglycemia before and after feeding (2.58 +/- 0.38 mmol/l, n = 13) and considerable postprandial galactosemia (3.26 +/- 1.38 mmol/l, n = 7). In the groups STARCH and FAT, glucose was only detectable in traces in urine, whereas all diets containing sugars led to glucosuria. In group SUC, fructose and sucrose were found in urine and in both lactose groups galactose and lactose were found. Diet GAL led to galactosuria (140 mmol galactose/l). In group LAC1, and especially in group GAL, galactitol was detected in urine. These results point to a rather limited capacity of the cat to metabolize sugars.

Animals↗

Sugar uptake and proton release by protoplasts from the infected zone of Vicia faba L. nodules: evidence against apoplastic sugar supply of infected cells.

Symbiotic dinitrogen fixation of legume nodules is fuelled by phloem-imported carbohydrates. These have to pass several cell layers to reach cells infected with Rhizobium bacteroids. It is unclear whether apoplastic steps are involved in carbohyd-rate translocation within the nodule. Protoplasts were isolated from the infected and uninfected cells of the central tissue of Vicia faba nodules using a recently developed protocol. These protoplasts were used to elucidate pathways for sugar transport in this tissue. Both types of protoplasts released protons into the medium. Acidification was inhibited by vanadate and erythrosin B. However, it was stimulated by fusicoccin only in uninfected cells. A symport of sugars with protons can therefore be energized in both cell types. Uptake of 14C-labelled sugars was determined using a phthalate centrifugation technique. Uninfected protoplasts accumulated glucose through high-affinity H+/glucose-symport that was not competitively inhibited by fructose or sucrose. Uninfected protoplasts also absorbed sucrose with biphasic kinetics. At 0.1, 1, and 10 mM sucrose, uptake was inhibited by CCCP. Fusicoccin did not stimulate the linear phase of sucrose uptake. Glucose inhibited sucrose uptake nearly completely. This was not related to sucrose cleavage in the medium because sucrose was absorbed at a much higher rate than glucose, and glucose concentration did not increase in sucrose-containing protoplast suspensions. By contrast with uninfected protoplasts, infected cells did not show transporter-mediated glucose or sucrose uptake. The findings underline a role of uninfected cells in sugar translocation. Infected cells are not apoplastically supplied with sugars and possibly depend on uninfected cells for carbon supply.

Carbohydrate Metabolism↗

Release of O-linked sugar chains from glycoproteins with anhydrous hydrazine and pyridylamination of the sugar chains with improved reaction conditions.

A method for preparation of pyridylamino (PA-) derivatives of O-linked sugar chains from glycoproteins was developed. A glycopeptide containing O-linked Gal beta 1-3GalNAc was prepared from fetuin and treated with anhydrous hydrazine followed by N-acetylation of free amino groups. Sugar chains released were pyridylaminated with improved reaction conditions and excess reagents were removed by gel filtration. Gal beta 1-3GalNAc-PA obtained together with PA-Gal as a by-product was quantified by HPLC. Conditions for the hydrazine treatment were investigated and the treatment at 40 degrees C for 350 h gave the best results for releasing O-linked sugar chains. The total yield of Gal beta 1-3GalNAc-PA from the glycopeptide was 53% under the established conditions and that of PA-Gal was 18%. The present method was applied to a glycoprotein, and the expected PA-O-linked sugar chains were obtained. Under these conditions, N-linked sugar chains were also released.

Acetylgalactosamine↗

Structural study of the sugar chains of human lactoferrin: finding of four novel complex-type asparagine-linked sugar chains.

Human lactoferrin contains 2 asparagine-linked sugar chains in 1 molecule. These sugar chains were released as oligosaccharides by hydrazinolysis from two lactoferrin samples of different races. The two oligosaccharide fractions gave exactly the same fractionation pattern upon paper electrophoresis and Bio-Gel P-4 column chromatography after sialidase digestion. A structural study of the oligosaccharides obtained from the two samples by sequential exoglycosidase digestion in combination with methylation analysis also gave the same results indicating that there is no racial difference both in quality and quantity of the sugar chain moiety of lactoferrin. In addition to the two acidic sugar chains, NeuAc alpha 2 leads to 6Gal beta 1 leads to 4GlcNAc beta 1 leads to 2Man alpha 1 leads to 6(NeuAc alpha 2 leads to 6Gal beta 1 leads 4GlcNAc beta 1 leads to 2Man alpha 1 leads to 3)Man beta 1 leads to 4GlcNAc beta 1 leads to 4(Fuc alpha 1 leads to 6)GlucNAc and Gal beta 1 leads to 4(Fuc alpha 1 leads to 3)GlcNAc beta 1 leads to 1Man alpha 1 leads to 6(NeuAc alpha 2 leads to 6Gal beta 1 leads 4GlcNAc beta 1 leads to 2Man alpha 1 leads to 3)Man beta 1 leads to 4GlcNAc beta 1 leads to 4(Fuc alpha 1 leads to 6)GlcNAc, and two novel acidic sugar chains, Gal beta 1 leads to 4(Fuc alpha 1 leads to 3)GlcNAc beta 1 leads to Man alpha 1 leads to 6(NeuAc alpha 2 leads to 6Gal beta 1 leads to 4GlcNAc beta 1 leads to 3Gal beta 1 leads to 4GlcNAc beta 1 leads to 2 Man alpha 1 leads to 3)Man beta 1 leads to 4GlcNAc beta 1 leads to 4(Fuc alpha 1 leads to 6(GlcNAc and Gal beta 1 leads to 4(Fuc alpha 1 leads to 3)GlcNAc beta 1 leads to 3Gal beta 1 leads to 4GlcNAc beta 1 leads to 2Man alpha 1 leads to 6(NeuAc alpha 2 leads to 6Gal beta 1 leads to 4GlcNAc beta 1 leads to 2Man alpha 1 leads to 3)Man beta 1 leads to 4GlcNAc beta 1 leads to 4(Fuc alpha 1 leads to 6)GlcNAc, were found to occur in human lactoferrin.

Asian People↗

Sugar specificity and sugar-proton interaction for the hexose-proton-symport system of Chlorella.

The substrate specificity of the glucose-proton symport system was studied to gain information about the spatial relationship between the binding sites for glucose and proton. Charged glucose analogues such as amino sugars or sugar acids were not transported by the uptake system, with the exception of 2-amino-2-deoxy-D-glucose. This glucosamine was taken up in the charged form in uniport mechanism, i.e. without symport of proton. This result was interpreted to mean that the proton-binding site of the symport system is close to the hydroxyl at carbon 2 of glucose. This interpretation was strengthened by the following facts: The steric position of hydroxyl groups at carbons 1, 2 or 3 of glucose were especially important for efficient transport. O-Methylation was not tolerated at carbon 1, but it was tolerated at carbons 3, 4 or 6. The stoichiometric flow of proton and sugar could be disturbed by removal of hydroxyl group at carbon 1 of glucose. The pH-dependence of sugar transport is sugar-specific, e.g. the amino group at carbon 2 of glucose improves transport at higher pH. The configuration at carbon 2 of glucose influences the specificity for the symported ion. It is concluded that the coupled flow of proton and glucose occurs by simultaneous coordinate movement of both in a transmembrane channel.

Biological Transport↗

Comparative study of the sugar chains of alkaline phosphatases purified from rat liver and rat AH-130 hepatoma cells. Occurrence of fucosylated high-mannose-type and hybrid-type sugar chains.

The N-linked sugar chains of alkaline phosphatases, purified from rat AH-130 hepatoma and from normal rat liver, were released quantitatively as oligosaccharides by hydrazinolysis and were labeled by reduction with NaB3H4. A comparative study of their structures revealed that following structural differences are induced by hepatocyte carcinogenesis: complex-type tetraantennary sugar chains and hybrid-type sugar chains appear; outer-chain moieties of the sugar chains of the hepatoma enzyme contain exclusively the Gal(Beta 1-4)GlcNAc groups (type 2 chains) but those of the normal enzyme contain other Gal(Beta 1-)GlcNAc groups and type 2 chains; and novel fucosylated high-mannose-type sugar chains are found in the oligosaccharides of the hepatoma enzyme.

Alkaline Phosphatase↗

Dental caries in pre-school children: associations with social class, toothbrushing habit and consumption of sugars and sugar-containing foods. Further analysis of data from the National Diet and Nutrition Survey of children aged 1.5-4.5 years.

This project examined the relative significance of dietary sugars, toothbrushing frequency and social class as predictors of caries experience (caries vs. no caries) among 1,450 British pre-school children who took part in the National Diet and Nutrition Survey. This cross-sectional survey was based on a representative sample of children aged 1.5-4.5 years studied in 1992/3. Children were classified into four groups according to social class and toothbrushing habit. Diet/caries associations were examined for biscuits and cakes, sugar confectionery, chocolate confectionery and soft drinks, and the percentage of energy from non-milk extrinsic sugars, using data on amount and frequency of consumption from 4-day weighed dietary records. In stepwise logistic regressions, the strength of the association between social class and caries experience was twice that between toothbrushing and caries, and nearly three times that between sugar confectionery and caries (other dietary variables were not significant). The association of caries with sugar confectionery (both in amount and frequency) was only present among children whose teeth were brushed less than twice a day. Toothbrushing frequency appeared to have a stronger impact on caries prevention in non-manual compared with manual children. Household expenditure on confectionery was associated with caries only among children from the manual group. The findings suggest the hypothesis that regular brushing (twice a day) with a fluoride toothpaste may have greater impact on caries in young children than restricting sugary foods.

Age Factors↗

Reducing the cariogenic effect of sugar by adding fluoride to sugar--project background.

For various reasons, the use of the more widely used fluoride vehicles--such as water, salt, and toothpastes--is not feasible in some communities. There is some theoretical and laboratory evidence to support the view that adding fluoride to sugar and sugar products has potential to reduce their cariogenic effect. However, the clinical evidence is minimal. The minimum concentration of fluoride in sugar which will bring about a caries-preventive effect needs to be determined. Logistical issues requiring investigation include the most efficient method of adding fluoride to sugar and the distribution and consumption patterns of sugar in target populations. The practical application of this knowledge to large populations is the priority focus of this investigation.

Cariostatic Agents↗

[The effects of indigestible dextrin on sugar tolerance: I. Studies on digestion-absorption and sugar tolerance].

It is widely acknowledged that high viscosity water-soluble dietary fibers such as pectin and guar gum affect a lowering of blood glucose levels and a reducing of insulin secretion following a sugar load. However, as dietary fibers vary in origin and in chemical properties, their physiological functions differ as well. In this study the effects of Indigestible Dextrin (PF-C), a low viscosity, water-soluble dietary fiber obtained through acid and heat-treatment of potato starch, on various aspects of sugar tolerance were examined. First, the influence of PF-C on sucrose hydrolysis was examined in rat intestinal mucosa cell homogenate confirming that PF-C did not inhibit sucrase activity. Then, in order to investigate the influence of PF-C on sugar digestion-absorption, an experiment was performed by using the everted intestinal sac of the rat in vitro. PF-C did not have an effect on glucose-transport into the serosal medium, whereas PF-C did inhibit the transport of hydrolyzed-glucose from sucrose, with no change in the hydrolysis of sucrose. Recently, Crane et al. reported that there is a specific route for hydrolyzed glucose from sucrose in glucose-absorption on the enteric surface (disaccharidase related transport system). The possibility exists that PF-C specifically affects this pathway. Further, total glucagon released into the serosal medium stimulated by both glucose and sucrose were reduced by PF-C. On the basis of these results, an oral sugar tolerance test was conducted in both rats and healthy human subjects. In male Sprague-Dawley rats (8 weeks old, 250-280g) concurrent administration of PF-C (0.6g/kg body weight) reduced an increase in plasma insulin levels with no change in glucose levels following a glucose (1.5g/kg body weight) load. Further noted were reductions in increases in both plasma glucose and insulin levels following a sucrose (1.5g/kg body weight) plus PF-C (0.6g/kg body weight) load to that of the sucrose (1.5g/kg body weight) single load. These findings reflect the above mentioned in vitro results. Moreover, in healthy male subjects the increase in both plasma insulin and glucagon-like immunoreactivity (Gut GLI) levels following a Trelan-G75 load were significantly reduced by concurrent administration of PF-C. From these observations it would appear that the effectiveness of reducing insulin secretion by PF-C results due to the decrease in sugar absorption by inhibiting the disaccharidase-related transport system.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗

H+-Coupled sugar transporter, an initiator of sugar-induced Ca2+-signaling in plant cells.

Using Ca2+-dependent photoprotein aequorin-transformed tobacco BY-2 cell suspensions, the sugar-induced increase in cytosolic free Ca2+ concentration ([Ca2+]cyt) was investigated by measuring the luminescence intensity. When 0.5 M sucrose or some other sugars were fed to the cells, strong and transient luminescence was observed. Salts or sugar analogues didn't show this effect. In addition, the intensity of sucrose-induced aequorin luminescence was gradually enhanced when cells were exposed to sugar-starvation. This was observed with the concurrent expression of the sucrose/H+ co-transporter, NtSUT1A. The [Ca2+]cyt increase may initiate Ca2+-signaling leading to the expression of genes related to biosynthesis of storage carbohydrates in a sink organ. The sugar-signaling may play an important role in the conversion on nutritional stage of plant tissue, source organ to sink organ.

Aequorin↗

Interrelationship between sugar-evoked increases in transmural potential difference and sugar influxes across the mucosal border in the small intestine.

The relationship between changes in the transmural potential induced by actively transported sugars(deltaPDs) and influxes of the sugars(Js's) was investigated in the isolated guinea pig small intestine. Under the condition that medium electrical conductivity. remains unchanged, deltaPD and Js were closely correlated, e.g., both showed very similar patterns of regional difference along the intestine, and the values of the half saturation concentration (Km) for a sugar estimated from electrical and flux measurements were nearly identical. No such correlation was observed when medium conductivity varied. However, a simple correction of the sizes of deltaPDs for medium conductivity restored a close parallelism between deltaPDs and Js's. The sugar-induced increase in Na+ flux estimated from the increase in short-circuit current varied in parallel with Js regardless of the medium conductivity, and a fixed stoichiometrical relationship (approximately one-to-one coupling) was seen between Na+ and sugar fluxes. It is concluded that the dominant factor affecting the interrelation between deltaPD and Js is the resistance of the paracellular shunt which is directly proportional to medium electrical conductivity

Animals↗

Identification of sugar-tolerant yeasts isolated from high-sugar fermented vegetable extracts.

In Japan, high-sugar fermented vegetable extracts are novel functional food products for which sugar-tolerant yeasts are employed during processing. In order to understand the yeast distribution in these foods and their role in the functionality of such foods, we isolated sugar-tolerant yeasts from nine sample products, together with one sample each of fermented extract of ume (Japanese apricot) and honey. Twenty-three strains were identified as Zygosaccharomyces rouxii; one strain as Z. bailii; one strain as Torulaspora delbrueckii; and one strain as Candida bombicola. Nearly 90% of the identified strains belonged to Z. rouxii with variations in fermentation and assimilation properties. All strains grew well on 50% w/w glucose medium, and all but two strains grew on 60% w/w glucose medium. Sixteen strains belonged to the strong sugar tolerance type (poor or no growth at 1% and maximum growth at 30 or 40% w/w glucose); four strains to the moderate type (grew well at 1% and maximum growth at 10 or 20% w/w glucose); and seven strains to the weak type (maximum growth only at 1% w/w glucose). One strain of Z. rouxii, V19, grew up to 80% (w/w) glucose in liquid medium. In view of salt tolerance, only two strains belonged to the moderate type (maximum growth at 0.5 or 1 m NaCl); the remaining strains all belonged to the weak type (maximum growth only at 0 m NaCl). This suggests that sugar tolerance and salt tolerance of yeasts have different aspects.

Journal Article↗

Effect of sugar analogues on growth, sugar utilization, and acid production by Streptococcus mutans.

Studies on the effect of various structural analogues of glucose of phosphoenolpyruvate (PEP)-dependent sugar transport in Streptococcus mutans showed that sugars with alterations at carbon 2 were markedly inhibitory. Low concentrations of the nonfermentable analogue D-2-deoxyglucose (2-deoxyg) blocked the growth of S mutans in broth media containing various fermentable sugars. Acid production by S mutans from both exogenous glucose and intracellular storage polysaccharide was inhibited by 2-deoxyG. The analogue is bacteriostatic, and large quantities of intracellular 2-deoxyG-6-PO4 accumulate during exposure of S mutans to the sugar.

Animals↗

A quantitative determination by capillary gas-liquid chromatography of neutral and amino sugars (as O-methyloxime acetates), and a study on hydrolytic conditions for glycoproteins and polysaccharides in order to increase sugar recoveries.

Complete gas-liquid chromatographic separation of O-methyloxime acetates (syn and anti isomers) prepared from eight neutral sugars, three hexosamines, and muramic acid has been obtained, using a fused-silica Carbowax 20M capillary column. A single hydrolytic step for carbohydrate-containing biological material (less than or equal to 2.5 X 10(-3) M sugar solution in 4 N trifluoroacetic acid at 125 degrees C for 1 h) has been developed, and results have been compared with those obtained with standard hydrolytic conditions in order to ensure complete release of amino sugars from glycoproteins, together with minimum losses of neutral sugars. The combination of this acid hydrolysis with the above improved derivatization procedure for the gas-liquid chromatographic analysis has led to a simple, rapid, and sensitive analytical method, which has been successfully tested on three glycoproteins (fetuin, mucin, and peroxidase) and two plant cell-wall polysaccharide fractions (soluble fibers from carrots and soybeans).

Amino Sugars↗