Configuration of the acetal carbon atom of pyruvic acid acetals in some bacterial polysaccharides

The configuration at the acetal carbon atom of pyruvic acid acetals present in some extracellular bacterial polysaccharides has been investigated. Assignment of the absolute configuration was made by comparing signals in the ¹³C- and ¹H-n.m.r. spectra of the polysaccharides with those of model substances. The S-configuration was demonstrated in eight polysaccharides in which pyruvic acid is linked to O-4 and O-6 of D-glucopyranosyl or D-mannopyranosyl residues. The R-configuration was demonstrated in four polysaccharides in which pyruvic acid is linked to O-4 and O-6 of D-galactopyranosyl residues. Consequently, in each of these acetals, which form 1,3-dioxane rings, the methyl group is equatorial and the carboxyl group axial. The S-form was further demonstrated in four polysaccharides in which the pyruvic acid is linked to O-3 and O-4 of D-galactopyranosyl groups.     

Occurrence of pyruvic acid in capsular polysaccharides (K antigens) of klebsiellas

The capsular polysaccharides of 77 Klebsiella K-types were analysed for the presence of pyruvic acid. One half of the polysaccharides investigated were found to contain between 1.3 and 12% of the keto acid. A comparison between the analyses performed and the calculated values from some pyruvic acid containing polysaccharides of known structure showed that there is only in 5 out of 10 cases a good correlation with a regular substitution of the oligosaccharide repeating units.     

奶油绚孔菌菌丝多糖的提取及其抗氧化活性

为了获得奶油绚孔菌菌丝多糖的最佳制备工艺并进一步评估其体外抗氧化的作用,本研究以奶油绚孔菌菌丝作为原料,采用中心组合试验法结合响应面分析法对奶油绚孔菌菌丝多糖的提取条件进行优化。结果表明,最佳的提取工艺为：料液比1:32、提取时间1.85 h和提取温度85 ℃,奶油绚孔菌菌丝多糖在此提取工艺条件下的得率为5.68%。奶油绚孔菌菌丝多糖对DPPH、ABTS和羟基自由基有清除能力,其EC₅₀分别为3.74、3.80和15.10 mg/mL。奶油绚孔菌菌丝多糖呈现出一定的还原能力。由此可知,奶油绚孔菌菌丝多糖具有一定的体外抗氧化作用,该研究能够为奶油绚孔菌菌丝多糖的进一步综合开发提供理论支持。     

Heparin inhibits proliferation of fetal vascular smooth muscle cells in the absence of platelet-derived growth factor

Proliferation of smooth muscle cells from the pulmonary arteries and aortas of fetal calves is inhibited by heparin in vitro. This effect is reversible and dose dependent. Comparisons with effects of other polysaccharides indicate that only extensively sulfated polysaccharides inhibit proliferation of smooth muscle cells but that specific structural features of heparin are required to achieve maximum effect. Heparin-Sepharose chromatography of medium containing fetal calf serum reduces the ability of that medium to promote growth of smooth muscle cells from fetal pulmonary arteries, suggesting that heparin may remove soluble growth factors in serum. However, inhibition of fetal pulmonary artery smooth muscle cell proliferation by heparin is identical in media supplemented either with serum prepared from fetal calf plasma, in which platelet-derived growth factor (PDGF) is not detectable, or with fetal calf serum, which contains relatively abundant PDGF (114 pg/ml). Thus, inhibition of fetal pulmonary artery smooth muscle cell proliferation by heparin is not mediated solely by decreased availability or activity of exogenous PDGF. These studies suggest that morphogenesis of the smooth muscle investment of the pulmonary arteries could be regulated by local production of heparin-like inhibitors of smooth muscle cell growth.     

Update on the possible mode of action of the jasmonates: Focus on the metabolism of cell wall polysaccharides in relation to growth and development

Jasmonic acid (JA) and its related compounds (jasmonates) applied to plant tissues exert either inhibitory or promotive effects in growth and developmental processes, which in some ways are similar to abscisic acid. However, little is known about the mode of action of the jamonates at the tissue or organ levels. Here, we review partial evidence for the physiological action of the jasmonates on cell elongation and abscission.
Jasmonates inhibit the IAA-induced cell elongation of oat coleoptile segments not by affecting energy production, osmoregulation and cell wall loosening, but by inhibiting the synthesis of cell wall polysaccharides. The inhibition is partially reversed by simultaneous application of sucrose. Inhibition of IAA-induced elongation by JA is only observed in monocotyledons, not in dicotyledons. These effects suggest that jasmonates exert their inhibitory effect on cell elongation by affecting the metabolism of the cell wall polysaccharides in monocotyledons.
Jasmonates promote the abscission of bean petiole explants without enhancing ethylene production. Cells in the petiole adjacent to the abscission zone expand during abscission. In the abscission zone, jasmonates decrease the amount of cellulosic but not that of noncellulosic polysaccharides. Jasmonates increase the activities of cellulase and decrease the levels of UDP-sugars, which are important intermediates for the synthesis of cell wall polysaccharides in the abscission zone, probably resulting in the decreased level of cellulose and the mechanical weakness of cell walls.
Thus, it is suggested that jasmonates exert their multiple physiological effects by affecting the metabolic processes of cell wall polysaccharides.     

Compositional difference of the exopolysaccharides produced by the virulent and virulence-deficient strains of Xanthomonas oryzae pv. oryzae

Xanthomonas oryzae pv. oryzae, the bacterial blight pathogen of rice, is known to produce phytotoxic polysaccharides. The extracellular polysaccharide (EPS) was isolated from virulent (BXO1) and virulence-deficient gum G mutant (BXO1002) strains of X. oryzae pv. oryzae and characterized using fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR). Data from the FT-IR suggested that the aldehyde (R-CHO) group and C=O of acid anhydride are present in BXO1 but absent in BXO1002. The (1)H-NMR spectra showed the presence of an acetyl amine of hexose or pentose, free amines of glucose, an beta-anomeric carbon of hexose and pentose, hydrogen next to hydroxyl group, an acetyl amine of hexose and pentose in the polysaccharides of both BXO1 and BXO1002, and the absence of alpha-anomeric carbon of hexose or pentose and the glucuronic acid in the polysaccharides produced by BXO1002. The test for glucuronic acid also confirmed the absence of glucuronic acid in the polysaccharides of BXO1002 and the presence glucuronic acid (32 microg/mg) in the polysaccharides produced by BXO1.     

Structural analysis of the carbohydrate components of the outer membrane of the lipopolysaccharide-lacking cellulolytic ruminal bacterium Fibrobacter succinogenes S85.

The polysaccharides from the outer membrane of the Gram-negative ruminal bacterium Fibrobacter succinogenes were isolated by phenol/water extraction and separated by size-exclusion chromatography in the presence of deoxycholate detergent into a lower-molecular-mass fraction designated 'glycolipid' and a high-molecular-mass 'capsular polysaccharide' fraction. Both fractions lacked typical lipopolysaccharide components including 2-keto-3-deoxyoctulosonic acid and 3-hydroxy fatty acids. Carbohydrate components of these fractions were represented by two polysaccharides and one oligosaccharide (possibly glycolipid) with the following structures: : : where HEAEP is N-(2-hydroxyethyl)-2-aminoethylphosphonic acid, found for the first time in natural compounds. The polysaccharides contained pentadecanoic acid and anteisopentadecanoic acid, possibly present as the acyl components. All constituent monosaccharides except L-rhamnose had a D-configuration. In addition to having a structural role in the outer membrane, these polysaccharides may provide protection for this lipopolysaccharide-less bacterium in the highly competitive ruminal environment, as phosphonic acids covalently linked to membrane polymers have in the past been attributed the function of stabilizing membranes in the presence of phosphatases and lipases.     

南瓜多糖对糖尿病大鼠血糖和血脂的影响

目的：研究南瓜多糖对糖尿病大鼠血糖和血脂的影响。方法：Wistar大鼠腹腔注射四氧嘧啶后。将成模的糖尿病大鼠根据血糖和体重随机分为糖尿病组、消渴丸组和南瓜多糖组,同时设立正常对照组,并分别给予蒸馏水、消渴丸和南瓜多糖灌胃,每周测量体重一次,四周后测定空腹血糖、血清总胆固醇、甘油三酯、高密度脂蛋白、低密度脂蛋白和游离脂肪酸的含量。结果：糖尿病组大鼠体重下降,血糖显著升高,甘油三酯、总胆固醇、低密度脂蛋白和游离脂肪酸含量显著增加,而高密度脂蛋白含量显著降低;补充南瓜多糖和消渴丸后,体重逐渐增加,血糖显著下降,总胆固醇、甘油三酯、低密度脂蛋白和游离脂肪酸含量显著降低,高密度脂蛋白含量显著升高,并且南瓜多糖的降糖降脂效果优于消渴丸。结论：南瓜多糖能增加体重,降低糖尿病大鼠血糖、血脂,对糖尿病及其并发症有一定的作用。     

Structural studies of the capsular polysaccharides from Klebsiella types 8 and 82, a reinvestigation

The structures of the capsular polysaccharides elaborated by Klebsiella types 8 (K8) and 82 (K82) have been reinvestigated. N.m.r. spectroscopy of the original and chemically modified polysaccharides was the principal method used. It is concluded that the polysaccharides are composed of repeating units having the following structures. (Formula: see text). The presence of L-glutamic acid, linked as an amide to the carboxyl group of a uronic acid, has not been observed hitherto in bacterial polysaccharides.     

Isolation and characterization of an alginase from mucoid strains of Pseudomonas aeruginosa.

Strains of Pseudomonas aeruginosa which produce an alginate-like slime polysaccharide were shown to also synthesize an intracellular enzyme which can degrade these polysaccharides and the seaweed alginic acids. The enzyme acts as an eliminase introducing delta 4,5 unsaturation into the uronic acid moiety. It appears to be a polymannuronide lyase which degrades the polysaccharides, depending on their uronic acid composition, to a series of oligosaccharides, the smallest of which is a disaccharide. L-Guluronic acid linkages are not split. The Pseudomonas alginase resembles other bacterial alginases and enzymes from molluscs but differs in some important properties, such as extent of degradation and linkage preference. Nonmucoid forms of the organism produce detectable but much lower amounts of enzyme.     

Diferulic and ferulic acid in the cell wall of Avena coleoptiles—Their relationships to mechanical properties of the cell wall

Alkaline hydrolysis liberated ferulic and diferulic acid from polysaccharides of the Avena coleoptile ( Avena sativa L. cv. Victory I) cell walls. The amount of the two phenolic acids bound to cell walls increased substantially at day 4–5 after sowing, when the growth rate of the coleoptile started to decrease. The level of these acids was almost constant from the tip to base in 3-day-old coleoptiles, but increased toward the basal zone in 4- and 5-day-old ones. The ratio of diferulic acid to ferulic acid was almost constant irrespective of coleoptile age and zone. An increase in the amount of ferulic and diferulic acids bound to cell wall polysaccharides correlated with a decrease in extensibility and with an increase in minimum stress-relaxation time and relaxation rate of the cell wall. The level of lignin in the cellulose fraction increased as coleoptiles aged, but this increase did not correlate with changes in mechanical properties of the cell walls. These results suggest that ferulic acid, ester-linked to cell wall polysaccharides, is oxidized to give diferulic acid, which makes the cell wall mechanically rigid by cross-linking matrix polysaccharides and results in limited cell extension growth. In addition, it is probable that the step of feruloylation of cell wall polysaccharides is rate-limiting in the formation of in-termolecular bridges by diferulic acid in Avena coleoptile cell walls.     

Preliminary chemical characterization of unusual eubacterial exopolysaccharides of deep-sea origin

Deep-sea hydrothermal vents are characterized by specific physical and chemical parameters including high pressure, high temperature gradients and high concentrations of toxic elements. Bacteria recovered from hydrothermal vents were studied for their capability to produce polysaccharides in normal conditions. A first screening performed on mesophilic aerobic bacterial strains led to the discovery of unusual polymers in terms of chemical composition and rheological properties. Neutral polysaccharides were found, along with uronic-rich exopolymers. In addition, a new sugar was identified in two polymers. Additional studies identified this compound as a hexuronic acid substituted with an ether-linked lactic acid. The sulfate content as estimated by FTIR indicated concentrations ranging from 2 to 21%. These high sulfate concentrations are uncommon in microbial polysaccharides and may lead to new applications in the pharmaceutical area. Uronic-rich exopolymers could be expected to have some heavy metal binding capability and applications in the fields of biodetoxification and wastewater treatment.     

抗补体活性多糖

补体系统在宿主免疫中具有重要的作用。近年来,由某些中药中纯化的多糖具有明显的抗补体作用。这些多糖大多数含有阿拉伯糖、半乳糖和半乳糖醛酸,分子量范围6.000到500.000。它们的结构很复杂,多为具聚鼠李半乳糖醛酸结构中心的酸性杂多糖和果胶类多糖。这些多糖的抗补体活性可能和整个大分子的结构有关。一旦发生降解活性就大为下降甚至消失。它们都可以经典的方式激活补体系统。大部分也可以改变的方式激活补体系统。     

A radiochemical approach to the determination of carboxylic acid groups in polysaccharides

A method for the routine radiochemical determination of carboxylic acid groups in polysaccharides is described. The procedure is based on sodium borotritide reduction of the product of the reaction between water-soluble carbodiimide derivatives and carboxyl groups on the polysaccharide. Carboxymethyl-cellulose and hyaluronic acid were used as test polysaccharides.     

Heterogeneity of the genus Myrothecium as revealed by cell wall polysaccharides

The polysaccharides obtained from the alkali-extractable, water-soluble fraction (F1SS) from the cell wall of Myrothecium verrucaria and Myrothecium atroviride were shown to be composed of beta-(1-->6)-galactofuranose fully substituted at O-2 by terminal residues of alpha-glucopyranose and alpha-glucuronic acid. Glucuronic acid was substituted at O-4 by glucopyranose in the Myrothecium species M. inundatum, M. setiramosum, M. prestonii, M. tongaense and M. roridum. The acidic polysaccharides from Phaeostilbella atra (=Myrothecium atrum) and Myrothecium gramineum lacked the backbone of 2,6 di-O-substituted galactofuranose and contained a high amount of O-5-substituted beta-galactofuranose. The structures of the polysaccharides isolated from Myrothecium cinctum and Myrothecium penicilloides were unrelated to each other and to the polysaccharides from the other species analysed. The usefulness of these polysaccharides as a characteristic for delimitation of the genus Myrothecium is discussed.     

Occurrence of L-iduronic acid and putative D-glucuronyl C5-epimerases in prokaryotes

Glycosaminoglycans (GAGs) are polysaccharides that are typically present in a wide diversity of animal tissue. Most common GAGs are well-characterized and pharmaceutical applications exist for many of these compounds, e.g. heparin and hyaluronan. In addition, also bacterial glycosaminoglycan-like structures exist. Some of these bacterial GAGs have been characterized, but until now no bacterial GAG has been found that possesses the modifications that are characteristic for many of the animal GAGs such as sulfation and C5-epimerization. Nevertheless, the latter conversion may also occur in bacterial and archaeal GAGs, as some prokaryotic polysaccharides have been demonstrated to contain L-iduronic acid. However, experimental evidence for the enzymatic synthesis of L-iduronic acid in prokaryotes is as yet lacking. We therefore performed an in silico screen for D-glucuronyl C5-epimerases in prokaryotes. Multiple candidate C5-epimerases were found, suggesting that many more microorganisms are likely to exist possessing an L-iduronic acid residue as constituent of their cell wall polysaccharides.     

Purification of Mycobacterial Deoxyribonucleic Acid

Impurities believed to be polysaccharides have been found in mycobacterial deoxyribonucleic acid (DNA) preparations. Agar-gel diffusion of the DNA preparations against concanavalin A indicated the presence of three polysaccharides and was used to follow the purification procedures. The polysaccharides appeared to be the same for all strains studied. Precipitation of DNA with cetyltrimethylammonium bromide was used to separate impurities from some DNA preparations. The presence of the contaminants was found to affect markedly the determination of the guanine plus cytosine content according to a method dependent on the ratio of absorbancies at 260 and 280 nm; the impurities did not affect the determination by the method of thermal denaturation. The presence of a DNA-polysaccharide complex is suggested.     

The structure of extracellular heteroglycans in various Cryptococcus species

Extracellular polysaccharides produced by some Cryptococcus species have been structurally investigated. These polymers have identical core structure, which was found to be alpha-1,3-mannan and different degrees of substitution of mannose in the core by xylose and glucuronic acid residues of side chains and different composition of side chains. Heteropolysaccharide from Cr. humicolus, the simplest one, has the same structure as the Cr. neoformans serotype D capsular polysaccharide. The Cr. skinneri polymer proved to be the most branched among Cryptococcus polysaccharides.     

The biosynthesis and functionality of the cell-wall of lactic acid bacteria

The cell wall of lactic acid bacteria has the typical Gram-positive structure made of a thick, multilayered peptidoglycan sacculus decorated with proteins, teichoic acids and polysaccharides, and surrounded in some species by an outer shell of proteins packed in a paracrystalline layer (S-layer). Specific biochemical or genetic data on the biosynthesis pathways of the cell wall constituents are scarce in lactic acid bacteria, but together with genomics information they indicate close similarities with those described in Escherichia coli and Bacillus subtilis, with one notable exception regarding the peptidoglycan precursor. In several species or strains of enterococci and lactobacilli, the terminal D-alanine residue of the muramyl pentapeptide is replaced by D-lactate or D-serine, which entails resistance to the glycopeptide antibiotic vancomycin. Diverse physiological functions may be assigned to the cell wall, which contribute to the technological and health-related attribut es of lactic acid bacteria. For instance, phage receptor activity relates to the presence of specific substituents on teichoic acids and polysaccharides; resistance to stress (UV radiation, acidic pH) depends on genes involved in peptidoglycan and teichoic acid biosynthesis; autolysis is controlled by the degree of esterification of teichoic acids with D-alanine; mucosal immunostimulation may result from interactions between epithelial cells and peptidoglycan or teichoic acids.     

Studies of molecular-weight distribution for hydrolysis products from some Klebsiella capsular polysaccharides

Gel-permeation chromatography has been used to determine the molecular-weight distribution of the products at various stages of acid hydrolysis of some capsular polysaccharides from klebsiella bacteria. Structurally significant oligosaccharides, which are believed to correspond closely to the chemical repeating units in the polysaccharide molecules, were detected together with products having higher molecular weights, which are clearly aggregates of these oligosaccharides. This constitutes good supporting evidence for the view that relatively simple sequences of sugars are repeated throughout the entire molecular structure of these polysaccharides, and quantitative information for the polysaccharides from three different Klebsiella strains (serotyped as k54, K4, and K64, respectively) has been obtained by this procedure. The study of the polysaccharide from Klebsiella K-type 54 has afforded both independent corroboration and some extension of available data.