Analytical and structural features of the gum exudate from Combretum hartmannianum schweinf.

The gum exudate from Combretum hartmannianum is water-soluble, forms very viscous solutions, and contains galactose (22%), arabinose (43%), mannose (10%), xylose (6%), rhamnose (4%), glucuronic acid (6%), 4-O-methylglucuronic acid (2%), and galacturonic acid (7%). The acidic components produced on hydrolysis of the gum were 6-O-(β-D-glucopyranosyluronic acid)-D-galactose, and two saccharides that had the same chromatographic mobility, and contained mannose and galacturonic acid, and galactose and 4-O-methylglucuronic acid, respectively. Methylation and methanolysis of the gum indicated the presence of terminal uronic acid, rhamnose, xylose, galactose, arabinofuranose, and arabinopyranose. Controlled, acid hydrolysis indicated the presence of (1→3)-linked arabinopyranose side-chains and (1→6)-linked galactose residues. C. hartmannianum gum, when subjected to two Smith-degradations, yielded Polysaccharides I and II, both of which contained galactose, arabinose, and mannose. Insufficient crude gum was available for a complete structural study, but the molecule was shown to contain long, sparsely branched chains of (1→6)-linked galactose residues, to which are attached (1→3)-linked arabinose and (1→3)-linked mannose side-chains.     

Hemicellulosic polymers from the leaves of coffea arabica

Polysaccharide fractions from leaves of Coffea arabica var. Mundo Novo were obtained by extraction with 24% potassium hydroxide solution and were found to contain rhamnose, arabinose, xylose, mannose, galactose, glucose, glucuronic acid and 4-O-methylglucuronic acid in different proportions. 2-Acetamido-2-deoxygalactose was detected in all fractions. The structures of the carbohydrate portions were analysed by methylation and Smith degradation. A high amount of 2,3,5-tri-O-methylarabinose and 2,3,4-tri-O-methylxylose units, which are related through end groups, suggested a large degree of branching in the polysaccharide fractions. Glucose was present mainly as (1 → 4)-linked residues, as indicated by the presence of 2,3,6-tri-O-methylglucitol in the hydrolysates of the methylated fractions. A greater proportion of monomethylxylitol in acidic fraction B-IV indicated that it was more branched than the others. The glucose and galactose residues are 4,6- and 3,4-di-O-substituted, respectively. Three successive Smith degradations gave mainly glycerol with some erythritol and threitol. In the linkage of carbohydrate—protein, the presence of O-glycosyl linkages between arabinose and hydroxyproline was indicated. A phenolic compound was detected in all polysaccharide fractions from leaves of the coffee tree and is probably derived from chlorogenic acid.     

Structural investigations of the extracellular polysaccharide elaborated by s19, a Xanthomonas-type bacterium

The extracellular, acidic heteropolysaccharide from Xanthomonas S19 consists of D-glucuronic acid, D-glucose, D-galactose, and D-mannose residues in the approximate molar ratios of 1.6:3:1:1, plus acetyl groups liked to C-2 and/or C-3 of a large proportion of the glucose residues. Methylation studies showed that the glucose is present as non-reducing end-group also as 1,2- and 1,4-linked units, the galactose residues are solely 1,3-linked, a major proportion of the mannose residues are 1,2,4-linked and the rest 1,2-linked. A high proportion of the glucuronic acid units are 1,4-linked. Periodate oxidation confirmed the presence of these linkages. The disaccharides D-Glc-(1→4)-D-Glc,D-Glc-(1→2)-D-Man, D-Glc-(1→3)-D-Gal, D-Gal-(1→2)-D-Glc, D-GlcA-(1→4)-D-GlcA, and β-D-GlcA-(1→4)-D-Man were isolated from a partial hydrolysate of the polysaccharide, and characterised. The similarities and differences between this polysaccharide and those from other Xanthomonas species are discussed.     

An arabinogalactan from the fibres of cotton (Gossypium arboreum L.)

An acidic arabinogalactan has been isolated from fibres of the cotton plant (Gossypium arboreum L.) at the stage of intensive secondary-wall formation. The polysaccharide contains arabinose, galactose, rhamnose, and glucuronic acid residues in the molar ratios 1:1.2:0.1:0.2. Periodate oxidation and methylation studies showed that there is a main chain of (1→3)-linked galactopyranosyl residues to which side chains are attached at O-6. The side chains consist of (1→6)-linked galactopyranosyl residues substituted at O-3 by (1→5)-linked arabinofuranosyl chains. Terminal galactopyranosyl, rhamnopyranosyl, and glucopyranuronosyl groups are also present. Enzymic hydrolysis showed that the configurations of the galactose and arabinose residues are d and l, respectively.     

Arabinogalactans in a purified allergen preparation from pollen of timothy (Phleum pratense)

The purified allergen preparation representing a certain fraction of an aqueous timothy pollen extractcontained ca. 20% carbohydrate, mainly as arabinose (7%) and galactose (13%). The protein content was 63%. Fractionation on DEAE-Sephadex and Sephadex G-100 gave one neutral and two acidic fractions, all containing protein, arabinose and galactose. The structure of the carbohydrate moiety was investigated by methylation analysis, periodate oxidation and enzyme incubation. The acidic fraction contained (1→6)-linked galactose residues, some being substituted on O-3 with arabinose. The neutral fraction consisted of a more extensively branched arabinogalactan with longer side chains of (1→3)- and (1→5)-linked arabinose. The arabinose was present mainly as α-l-arabinofuranosyl residues. Alkaline degradation and subsequent fractionation indicated the presence of a covalent linkage between hydroxyproline and arabinose. Periodate oxidation or incubation with α-l-arabinofuranosidase did not affect the allergenic activity of the extract.     

Some structural features of a new sulphated heteropolysaccharide from Padina pavonia

An acid-extractable, water-soluble, polysaccharide sulphate, isolated from Padina pavonia, comprised variable proportions of glucuronic acid, galactose, glucose, mannose, xylose, and fucose in addition to a protein moiety. Partial acid hydrolysis and autohydrolysis of the free acid polysaccharide yielded several oligosaccharides. Evidence from periodate oxidation studies indicated that the inner polysaccharide portion is composed of (1 → 4)-linked β-D-glucuronic acid, (1 → 4)-linked β-D-mannose and (1 → 4)-linked β-D-glucose residues. The heteropolymeric partially sulphated exterior portion is attached to the inner part and comprises various ratios of (1 → 4)-linked β-D-galactose, β-D-galactose-3-sulphate residues, (1 → 4)-linked β-D-glucose residues, (1 → 2)-linked α-L-fucose 4-sulphate residues and (1 → 3)-linked β-D-xylose residues.     

Glycoproteins of the opium poppy

Two carbohydrate-protein fractions were isolated from the water-soluble biopolymer from opium poppy capsules by chromatography on SP-Sephadex. The carbohydrate chains are composed of arabinose, rhamnose, xylose, mannose, glucose, galactose, galacturonic acid, glucuronic acid and 4-O-methyl glucuronic acid. Methylation analysis indicated a high degree of branching suggesting a very complex structure. Treatment of the glycoprotein with NaOH in the presence of NaBH₄ resulted in a significant decrease in the serine and threonine content. The carbohydrate side chains released contained the sugar alcohol, galactitol. These results indicate that polysaccharide chains are linked to protein via serine-O-galactoside linkages.     

Purification and partial characterization of a procaryotic glycoprotein from the plasma membrane of Thermoplasma acidophilum

The obligate, thermophilic, acidophilic mycoplasma, Thermoplasma acidophilum, grows optimally at 56° C and pH 2.0. Its plasma membrane possessed 21–22 protein bands that were resolved by polyacrylamide gel electrophoresis. One major membrane protein, molecular weight 152 000, which stained for carbohydrate with periodic acid-Schiff reagent, accounted for 32% (w/w) of the total membrane proteins. It was isolated and further purified by concanavalin A affinity chromatography. The carbohydrate content amounted to less than 10% (w/w) compared to that of the entire glycoprotein. The carbohydrate moiety consisted mainly of mannose residues with branched α 1 → 2 linkages at the non-reducing ends of the glycopeptide as determined by permethylation followed by gas chromatography-mass spectrometry analysis. The reducing end was an N-glycosidic linkage between asparagine and N-acetylglucosamine. The amino acid composition of this glycoprotein showed 62 mol% hydrophobic residues, while the acidic amino acid content contributed 9 mol% more than that of the basic amino acids. The existence of membrane glycoproteins in the procaryotic, wall-less T. acidophilum may provide a protective coat for the plasma membrane. The stereochemistry and the conformation of the carbohydrate chains, in conjunction with water turgor, may contribute to the rigidity of the membrane and the cation binding.     

Microheterogeneity of the inner core region of yeast manno-protein

The inner core linkage region fragment from Saccharomyces cerevisiae mannan has been fractionated into 6 components and their structures have been analyzed. They form a family of homologous oligosaccharides (Man₁₂GNAc to Man₁₇GNAc) with 6 or 7 mannose units in α1→6 linkage attached to N-acetylglucosamine by a β1→4 linkage, and with different amounts of side chain mannose units attached by α1→2 and α1→3 linkage.     

东北红豆杉多糖的化学研究

利用水提醇沉提取东北红豆杉多糖TP,经超滤得到超滤外液TP-1和内液TP-2。TP-2进行部分酸水解和凝胶柱层析分离纯化,得到TP-2-1a。通过对理化性质、分子量、单糖组成和甲基化测定结果分析,确定其分子量分布在7.0 kDa左右,糖组成由Rha、Man、Gal、Glu、GalA和GlcA构成,摩尔比为:16.9∶1.0∶15.5∶1.3∶9.9∶2.5,中性糖以Gal的1→3、1→4连接为主,在1→3连接的O-6位上有分支;Rha以1→2连接为主,在O-4位上有分支;Man以1→4、1→6连接为主;Glu以1→3、1→4连接为主;非还原末端主要是Gal及少量的Man、Glu和Rha。酸性糖以1→4连接GalA为主,无分支。该多糖为首次从东北红豆杉中分离得到。     

Product-identification and substrate-specificity studies of the GDP-l-fucose: 2-acetamido-2-deoxy-β-d-glucoside (fuc→asn-linked GlcNAc) 6-α-l-fucosyltransferase in a golgi-rich fraction from porcine liver

Golgi-rich membranes from porcine liver have been shown to contain an enzyme that transfers l-fucose in α-(1→6) linkage from GDP-l-fucose to the asparagine-linked 2-acetamido-2-deoxy-d-glucose r residue of a glycopeptide derived from human α₁-acid glycoprotein. Product identification was performed by high-resolution, ¹H-n.m.r. spectroscopy at 360 MHz and by permethylation analysis. The enzyme has been named GDP-l-fucose: 2-acetamido-2-deoxy-β-d-glucoside (Fuc→Asn-linked GlcNAc) 6-α-l-fucosyltransferase, because the substrate requires a terminal β-(1→2)-linked GlcNAc residue on the α-Man (1→3) arm of the core. Glycopeptides with this residue were shown to be acceptors whether they contained 3 or 5 Man residues. Substrate-specificity studies have shown that diantennary glycopeptides with two terminal β-(1→2)-linked GlcNAc residues and glycopeptides with more than two terminal GlcNAc residues are also excellent acceptors for the fucosyltransferase. An examination of four pairs of glycopeptides differing only by the absence or presence of a bisecting GlcNAc residue in β-(1→4) linkage to the β-linked Man residue of the core showed that the bisecting GlcNAc prevented 6-α-l-fucosyltransferase action. These findings probably explain why the oligosaccharides with a high content of mannose and the hybrid oligosaccharides with a bisecting GlcNAc residue that have been isolated to date do not contain a core l-fucosyl residue.     

Purification and methylation analysis of cell wall material from Solanum tuberosum

Cell wall material (CWM) of potatoes was prepared by sequentially extracting the wet ball-milled tissue with 1 % aq. Na deoxycholate, PhOHHOAcH₂O and 90 % (v/v) aq. DMSO. The purity of the CWM (e.g. absence of residual starch) was established by carbohydrate analysis using different acid hydrolysis conditions and by methylation studies. The partially methylated alditol acetates from the CHCl₃MeOH soluble fraction (S) of the methylated CWM were separated into 15 main peaks by GLC. Fourteen of these peaks were carbohydrate derivatives and the identity of most of these was established by MS. Reduction of the hydrolysate of S with NaBD₄ was used to identify the carbohydrate derivatives present in peaks 7 and 11 above. The occurrence of 4-linked galacturonosyl residues in the methylated polymers was established after reduction of S with LiAlH₄ and LiAlD₄. The main glycosidic linkages present in the non-cellulosic polysaccharides of the wall in descending order of concentration are: 4-linked galactose, 4-linked galacturonic acid, 5-linked arabinose and 4,6-linked glucose. The major branch points are those through 0–6 of glucose and 0–4 of rhamnose. Arabinose, galactose and xylose residues constituted the non-reducing ends. Graded acid hydrolysis of the CWM made it possible to assess the relative strengths of some of the glycosidic linkages. The general structural features of the CWM are discussed in the light of these results.     

A galactoglucomannan from the leaf and stem tissues of red clover (Trifolium pratense)

A galactoglucomannan has been isolated by fractionation of the alkali-soluble hemicelluloses of the leaf and stem tissues of red clover (Trifolium pratense L.). The hemicellulose contains galactose, glucose, and mannose residues in the molar ratios 0.25:1.0:1.1 and accounts for ca. 25% of the mannose residues present in the clover tissues. Structural studies showed that the hemicellulose has a main chain of β-(1→4)-linked D-glucopyranosyl and D-mannopyranosyl residues, to which are attached α-(1→6)-linked D-galactopyranosyl residues.     

Structural studies of water-soluble glycoproteins from Cannabis sativa L

Two carbohydrate-protein fractions, isolated from Cannabis sativa L. by extraction with water and chromatography on DEAE-cellulose, contained arabinose, galactose, glucose, mannose, galacturonic acid, 2-acetamido-2-deoxyglucose, and 2-acetamido-2-deoxygalactose. The structure of the carbohydrate moieties was investigated by methylation analysis and Smith degradation. A high percentage of end-groups indicates a large degree of branching, glucose and galactose being the main branch-points, linked at C-3 and C-6. The hexoses are also present as unbranched residues in the chain, largely as (1→3)- and (1→4)-linked units and as end-groups. Arabinofuranosyl units constitute the main part of the non-reducing end-groups, and are also present as part of the chain. The polysaccharide chains are probably linked to protein through the hydroxyl group of hydroxyproline.     

Structural study of the extracellular polysaccharide gum from Rhizobium strain CB744

The structure of the extracellular polysaccharide gum from nitrogen-fixing Rhizobium sp. strain CB744 (a member of the slow-growing Cowpea group) has been investigated. Gas-chromatographic analysis of the alditol acetates of the acid hydrolysate showed the gum to be composed of galactose, 4-O-methylgalactose, mannose, and glucose in the molar ratio of 1:2.5:3.5:7.0. The polysaccharide is unusual in that it contains no carbonyl substituent, although such substituents are common amongst polysaccharides produced by the slow-growing group. The native and de-branched polysaccharides were examined by methylation analysis. The anomeric configurations were determined by ¹³C-n.m.r. and oxidation by chromium trioxide. It is concluded that there are two β-(1→4)-linked glycopyranosyl residues for each α-(1→4)-linked mannopyranosyl residue, and that each mannose is substituted at O-6 by a β-galactopyranosyl residue, with 71% of the galactose groups being present as 4-O-methylgalactose.     

Comparative studies of asparagine-linked oligosaccharide structures of rat liver microsomal and lysosomal beta-glucuronidases

The sugar chains of microsomal and lysosomal β-glucuronidases of rat liver were studied by endo-β-N-acetylglucosaminidase H digestion and by hydrazinolysis. Only a part of the oligosaccharides released from microsomal β-glucuronidase was an acidic component. The acidic component was not hydrolyzed by sialidase and by calf intestinal and Escherichia coli alkaline phosphatases, but was converted to a neutral component by phosphatase digestion after mild acid treatment indicating the presence of a phosphodiester group. The neutral oligosaccharide portion of microsomal enzyme was a mixture of five high mannose-type sugar chains: (Manα1 → 2)_0~4 [Manα1 → 6(Manα1 → 3)Manα1 → 6(Manα1 → 3)Manβ1 → 4GlcNAcβ1 → 4GlcNAc]. In contrast, lysosomal enzyme contains only Manα1 → 6 (Manα1 → 3) Manα1 → 6(Manα1 → 3) Manβ1 → 4GlcNAcβ1 → 4GlcNAc. The result indicates that removal of α1 → 2-linked mannosyl residues from (Manα1 → 2)₄[Manα1 → 6(Manα1 → 3)Manα1 → 6(Manα1 → 3)Manβ1 → 4GlcNAcβ1 → 4GlcNAc → Asn] starts already in the endoplasmic reticulum of rat liver.     

4-O-Methylglucuronoxylan Isolated from the Midrib of Nicotiana tabacum

An acidic xylan from the midrib of Nicotiana tabacum was isolated by alkaline extraction and fractionation on a DEAE-cellulose column. Based on the results of methylation analysis, partial acid hydrolysis and Smith degradation, the acidic xylan was concluded to be composed of a linear backbone of β-(1→4)-linked D-xylopyranosyl residues with approximately every ninth residue carrying a terminal 4-O-methyl-α-D-glucopyranosyluronic acid residue linked as a single side chain by (1→2) linkage.     

Oligosaccharides on cathepsin D from porcine spleen

Cathepsin D from porcine spleen contained mannose (3.3%), glucosamine (1.4%), and mannose 6-phosphate (0.08%). Essentially all of the oligosaccharides of cathepsin D could be released by endo-β-N-acetylglucosaminidase H, pointing to oligomajmoside types of structures. Three neutral oligosaccharide fractions, containing 5, 6, and 7 mannose residues, respectively, were isolated by gel permeation chromatography on Bio-Gel P-2. Studies using exoglycosidase digestions and 500-MHz ¹H NMR spectroscopy revealed that their structures are [Manα1 → 2]_{0 or 1}Manα1 → 6[Manα1 → 3]Manα1 → 6[(Manα1 → 2)_{0 or 1}Manα1 → 3]Manβ1 → 4GlcNAcβ1 → 4 GlcNAc. These structures are identical to what have recently been proposed by Takahashi et al. for the major oligosaccharide units of cathepsin D from the same source (T. Takahashi P.G. Schimidt, and J. Tang (1983)J. Biol. Chem.258, 2819–2930), except for the occurrence of two isomeric oligosaccharides containing six mannoses. Only a part (3.4%) of the oligosaccharides were acidic, containing phosphates in monoester linkage. The phosphorylated oligosaccharides also consisted of oligomannoside-type chains which were analogous to, but more heterogeneous in size than the neutral oligosaccharides. Cathepsin D was bound to a mannose- and N-acetylglucosamine-specific lectin (mannan-binding protein) isolated from rabbit liver with the K_i value of 5.4 × 10^?6m.     

The structure of the neutral polysaccharide gum secreted by Rhizobium strain cb744

A previous investigation of the structure of the extracellular polysaccharide gum from the nitrogen-fixing Rhizobium strain cb744 (a member of the slow-growing Cowpea group) indicated that there were two β-(1→4)-linked d-glucopyranosyl residues for each α-(1→4)-linked d-mannopyranosyl residue, and that each mannose was substituted at O-6 by a β-d-galactopyranosyl residue having 71% of the galactose present as 4-O-methylgalactose. The present study shows that, although the gum appeared to have a simple tetrasaccharide repeating unit, it is composed of two closely associated components. One is a (1→4)-linked α-d-mannan substituted at each O-6 by a β-d-galactopyranosyl residue (71% 4-O-methylated). The second component is a (1→4)-linked β-d-glucan. The existence of the two polysaccharides was established by separation of the β-d-galactosidase-treated gum on a column of concanavalin A-Sepharose 4B. The d configurations were determined and the anomeric attribution of the linkages confirmed by the use of enzymes. The interaction between the two gum components is discussed.     

Structure of l-arabino-d-galactan-containing glycoproteins from radish leaves

Two l-arabino-d-galactan-containing glycoproteins having a potent inhibitory activity against eel anti-H agglutinin were isolated from the hot saline extracts of mature radish leaves and characterized to have a similar monosaccharide composition that consists of l-arabinose, d-galactose, l-fucose, 4-O-methyl-d-glucuronic acid, and d-glucuronic acid residues. The chemical structure features of the carbohydrate components were investigated by carboxyl group reduction, methylation, periodate oxidation, partial acid hydrolysis, and digestion with exo- and endo-glycosidases, which indicated a backbone chain of (1→3)-linked β-d-galactosyl residues, to which side chains consisting of α-(1→6)-linked d-galactosyl residues were attached. The α-l-arabinofuranosyl residues were attached as single nonreducing groups and as O-2- or O-3-linked residues to O-3 of the β-d-galactosyl residues of the side chains. Single α-l-fucopyranosyl end groups were linked to O-2 of the l-arabinofuranosyl residues, and the 4-O-methyl-β-d-glucopyranosyluronic acid end groups were linked to d-galactosyl residues. The O-α-l-fucopyranosyl-(1→2)-α-l-arabinofuranosyl end-groups were shown to be responsible for the serological, H-like activity of the l-arabino-d-galactan glycoproteins. Reductive alkaline degradation of the glycoconjugates showed that a large proportion of the polysaccharide chains is conjugated with the polypeptide backbone through a 3-O-d-galactosylserine linkage.