Thermochemical pretreatment of lignocellulose to enhance methane fermentation: I. Monosaccharide and furfurals hydrothermal decomposition and product formation rates

Over a pH range 1-4 and temperatures from 170 to 230 degrees C, the decomposition rates of xylose, galactose, mannose, glucose, 2-furfural, and 5-hydroxymethyl-2-furfural (5-HMF) were pseudo first order. The effect of temperature and pH on the pseudo first-order decomposition rate constants was modeled using the Arrhenius equation and acid-base catalysis, respectively. Decomposition rates of the monosaccharides were minimum at a pH 2-2.5. Above pH 2.5, the monosaccharide decomposition was base catalyzed, with acid catalysis occurring at a pH of less than 2 for glucose. The furfurals were subject to acid catalysis at below ca. pH 3.5. The hydrothermal conversion of glucose to its decomposition products during thermochemical Pretreatment can be modeled as a combination of series and parallel reactions. The formation rates of identified soluble products from glucose decomposition, 5-HMF and levulinic acid, were also functions of temperature and pH. The rate of 5-HMF formation relative to glucose decomposition decreased as the pH increased from 2.0 to 4.0, with levulinic acid formation only detected when the pH was 2.5 or less. For glucose decomposition, humic solids accounted for ca. 20% of the decomposition products.     

Characterization of an extracellular polysaccharide produced by a Pseudomonas strain grown on glycerol

A new extracellular charged polysaccharide composed mainly by galactose, with lower amounts of mannose, glucose and rhamnose, was produced by the cultivation of Pseudomonas oleovorans NRRL B-14682 using glycerol as the sole carbon source. Thermal and solid-state NMR analysis showed that this polymer is essentially amorphous, with a glass transition temperature of 155.7 degrees C. The exopolysaccharide aqueous solutions have viscoelastic properties similar to that of Guar gum, but with affinity to salts as a result of its polyelectrolyte character. In addition, the exopolysaccharide has demonstrated good flocculating and emulsifying properties and film-forming capacity. These properties make this polymer a good alternative to more expensive natural polysaccharides, such as Guar gum, in several applications in the food, pharmaceutical, cosmetic, textile, paper and petroleum industries.     

Glycoprotein biosynthesis in animal cells grown in suspension culture. Assembly of lipid-linked saccharides and formation of protein-bound ''high-mannose'' oligosaccharides.

Glycoprotein biosynthesis was studied with mouse L-cells grown in suspension culture. Glucose-deprived cells incorporated [3H]mannose into 'high-mannose' protein-bound oligosaccharides and a few relatively high-molecular-weight lipid-linked oligosaccharides. The latter were retained by DEAE-cellulose and turned over quite slowly during pulse--chase experiments. Increased heterogeneity in size of lipid-linked oligosaccharides developed during prolonged glucose deprivation. Sequential elongation of lipid-linked oligosaccharides was also observed, and conditions that prevented the assembly of the higher lipid-linked oligosaccharides also prevented the formation of the larger protein-bound 'high-mannose' oligosaccharides. In parallel experiments, [3H]mannose was incorporated into a total polyribosome fraction, suggesting that mannose residues were transferred co-translationally to nascent protein. Membrane preparations from these cells catalysed the assembly from UDP-N-acetyl-D-[6-3H]glucosamine and GDP-D-[U-14C]mannose of polyisoprenyl diphosphate derivatives whose oligosaccharide moieties were heterogeneous in size. Elongation of the N-acetyl-D-[6-3H]glucosamine-initiated glycolipids with mannose residues produced several higher lipid-linked oligosaccharides similar to those seen during glucose deprivation in vivo. Glucosylation of these mannose-containing oligosaccharides from UDP-D-[6-3H]glucose was restricted to those of a relatively high molecular weight. Protein-bound saccharides formed in vitro were mainly smaller in size than those assembled on the lipid acceptors. These results support the involvement of lipid-linked saccharides in the synthesis of asparagine-linked glycoproteins, but show both in vivo and in vitro that protein-bound 'high-mannose' oligosaccharide formation can occur independently of higher lipid-linked oligosaccharide synthesis.     

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.     

Involvement of Lipid-linked Oligosaccharides in Synthesis of Storage Glycoproteins in Soybean Seeds

Membrane preparations from developing soybean (var. Prize) cotyledon tissue, at the time of synthesis of storage glycoproteins, catalyze the sequential assembly of lipid-linked oligosaccharides from uridine-5'-diphospho-N-acetyl-d-[6-(3)H] glucosamine and guanosine-5'diphospho-d-[U-(14)C]mannose. The maximum size of lipid-linked oligosaccharide that accumulates contains the equivalent of 10 saccharide units on the basis of Bio-Gel P-2 gel filtration studies. These lipid-linked oligosaccharides show similar characteristics to polyisoprenyl diphosphate derivatives on diethylaminoethyl-cellulose chromatography and are potential intermediates in glycoprotein biosynthesis in this tissue. These glycolipids do not appear to turn over in pulse-chase experiments and no completed storage glycoproteins were detected among the products of these incubations.Tissue slices from cotyledons at the same stage of development synthesize lipid-linked oligosaccharides from [(3)H]mannose and [(3)H]glucosamine with sizes equivalent to 1, 7, 10, and approximately 15 saccharide units. In pulse-chase experiments, the lipid-linked saccharides with the equivalent of 1 and 10 units rapidly turnover, whereas those with 7 and 15 units do not. Examination of the higher oligosaccharide peaks (10 and 15) by Bio-Gel P-4 gel filtration shows them to comprise 2 distinct subsets of oligosaccharides containing different proportions of glucosamine and mannose units. Tissue slices synthesize products which resemble the completed 7S storage glycoproteins as judged by similarity of molecular weight and precipitation with specific antisera. Analysis of the oligosaccharides obtained by hydrazinolysis of glycoproteins shows the presence of a similar size "high-mannose" type N-linked oligosaccharides as in other glycoproteins from animal and plant cells.     

New feature of angiotensin-converting enzyme: carbohydrate-recognizing domain

Self carbohydrate-mediated dimerization of glycoprotein angiotensin-converting enzyme (ACE) was demonstrated. The dimerization was studied in the reverse micelle experimental system as a model of biomembrane situation. Asialo-ACE or agalacto-ACE was able to form a dimer, whereas deglycosylated ACE and sequentially desialylated and degalactosylated ACE failed to dimerize. ACE-ACE interaction was competitively inhibited by Neu5Ac- or Gal-terminated saccharides. The results have allowed us to propose the existence of carbohydrate-recognizing domain (CRD) on ACE molecule. The structural requirements of this CRD were estimated based on the ability of saccharides to inhibit ACE dimerization. The most effective monosaccharides with equal inhibition potencies were shown to be galactose (as GalbetaOMe) and N-acetylneuraminic acid (as Neu5AcalphaOMe). Among oligosaccharides, the most effective ones were found to be 3'SiaLac and, especially, the whole pool of ACE oligosaccharide chains and biantennae complex oligosaccharide chains of other glycoproteins. Bovine and human ACEs were shown to be similar in terms of recognition of carbohydrates.     

Conditions of formation, purification, and characterization of an alpha-galactosidase of Trichoderma reesei RUT C-30.

Trichoderma reesei RUT C-30 formed an extracellular alpha-galactosidase when it was grown in a batch culture containing lactose or locust bean gum as a carbon source. Short-chain alpha-galactosides (melibiose, raffinose, stachyose), as well as the monosaccharides galactose, dulcitol, arabinose, and arabitol, also induced alpha-galactosidase activity both when they were used as carbon sources (at a concentration of 1%) in batch cultures and in resting mycelia (at concentrations in the millimolar range). The addition of 50 mM glucose did not affect the induction of alpha-galactosidase formation by galactose. alpha-Galactosidase from T. reesei RUT C-30 was purified to homogeneity from culture fluids of galactose-induced mycelia. The active enzyme was a 50 +/- 3-kDa, nonglycosylated monomer which had an isoelectric point of 5.2. It was active against several alpha-galactosides (p-nitrophenyl-alpha-D-galactoside, melibiose, raffinose, and stachyose) and galactomannan (locust bean gum) and was inhibited by the product galactose. It released galactose from locust bean gum and exhibited synergism with T. reesei beta-mannanase. Its activity was optimal at pH 4, and it displayed broad pH stability (pH 4 to 8). Its temperature stability was moderate (60 min at 50 degrees C resulted in recovery of 70% of activity), and its highest level of activity occurred at 60 degrees C. Its action on galactomannan was increased by the presence of beta-mannanase.     

Production of oligosaccharides by autohydrolysis of brewery's spent grain

Brewery's spent grain was treated with water in a process oriented towards the production of xylo-oligosaccharides (XOS). A wide range of temperatures and reaction times were tested and the effects of these operational variables on hemicellulose solubilization and reaction products were investigated. The maximal XOS yield (61% of the feedstock xylan) was obtained at 190 degrees C after 5 min of reaction. Several oligosaccharide mixtures with different molecular weight distributions were obtained depending on temperature and reaction time. Longer reaction times led to decreased oligosaccharide production and enhanced concentrations of monosaccharides, sugar decomposition products and acetic acid. With reaction times leading to the maximal yields of XOS, little decomposition into organic acids and aldehydes was found at all the temperatures assayed. From the composition of processed solids, it was calculated that 63-77% of the initial xylan was selectively solubilized in autohydrolysis treatments.     

Exploring the structural diversity of mammalian carbohydrates ("glycospace") by statistical databank analysis.

The diversity of three major classes of mammalian carbohydrates, mainly glycolipids and O- and N-linked glycans, deposited in the databank GLYCOSCIENCES.de was subjected to statistical analyses. Size, chain length, and branching complexity were accessed and revealed that the average oligosaccharide is composed of about eight monosaccharide units. About a quarter of all oligosaccharides are strictly linear, and the remainder are branched at least once. Glucosamine, galactose, and mannose are dominating and comprise ~75% of the monosaccharides within mammalian oligosaccharide frameworks. alpha-Linked sialic acid, alpha-linked fucose, and beta-linked galactose decorate the majority of reducing termini. Glucose as the most abundant carbohydrate in mammals plays only a very minor role within these structures. Particular emphasis was placed on analyzing the way the monosaccharide units are linked within the oligomeric framework. Just 11 monosaccharide connections account for >75% of all linkages. Thus, the number of structural combinations found in nature, the part of the occupied mammalian glycospace, is much smaller than expected. As a result, a potential set of building blocks for oligosaccharide assembly is presented. This potential building block set was correlated with the accessible 3299 mammalian carbohydrate structures in the GLYCOSCIENCES.de databank. Only 36 building blocks are required to construct 75% of the 3299 mammalian oligosaccharides.     

The effect of tsushimycin on the synthesis of lipid-linked saccharides in aorta.

The antibiotic, tsushimycin, inhibits the formation of dolichyl phosphate mannose, dolichyl phosphate glucose and dolichyl pyrophosphate N-acetylglucosamine in the particulate enzyme preparation from pig aorta. Although this antibiotic also inhibits the incorporation of mannose and glucose into lipid-linked oligosaccharides, these reactions are less sensitive to antibiotic than those involved in the synthesis of lipid-linked monosaccharides. In the presence of tsushimycin, most of the mannose incorporated into lipid-linked oligosaccharides is into one oligosaccharide that has the properties of the heptasaccharide Man5GlcNAc2, whereas in the absence of antibiotic most of the mannose is in larger-sized oligosaccharides. On the other hand, the glucose-labelled lipid-linked oligosaccharides appear to be similar in size in the presence or absence of antibiotic. Tsushimycin also inhibits the formation of lipid-linked monosaccharides by the solubilized enzyme preparation of aorta. Various concentrations of dolichyl phosphate or the detergent, Nonidet P40, had no effect on antibiotic inhibition. Some evidence indicates that tsushimycin binds to the particulate enzyme.     

Protoplast isolation and culture from carob (Ceratonia siliqua) hypocotyls: ability of regenerated protoplasts to produce mannose-containing polysaccharides

The aim of this study was to isolate protoplasts from carob (Ceratonia siliqua L.) embryonic tissues with the ability to regenerate cell walls, divide and synthesize galactomannan, a valuable polysaccharide for industry. Protoplasts isolated from carob hypocotyl hooks regenerated cell walls within 24 h. The first divisions of the regenerated cells were observed after 2 days of culture. The highest percentage that successfully divided was achieved when the seedlings were grown under diffuse light, the hypocotyl hooks were plasmolysed for 1 h before incubation in the protoplast isolation solution and the protoplasts were cultured under diffuse light. After 9 days of culture, cell clusters, consisting of eight cells, had been produced, which underwent further mitotic divisions and which were expected to lead to callus formation. Polysaccharide and oligosaccharide synthesis during protoplast regeneration was studied by radiolabelling with exogenous d ‐[U‐¹⁴C]glucose, d ‐[U‐¹⁴C]mannose or d ‐[2‐³H]mannose, which gave rise to uniform, moderately specific and highly specific labelling, respectively. As revealed by the radioactivity distribution in cell wall monosaccharides, the regenerants deposited new wall polymers that differed markedly from those being synthesized by the hypocotyls from which the protoplasts had been isolated. The regenerants deposited large amounts of callose and smaller amounts of galactose‐, arabinose‐ and mannose‐containing polymers. The latter included glucuronomannan, as demonstrated by a new method involving partial acid hydrolysis followed by β‐glucuronidase (EC 3.2.1.31) digestion. The regenerating protoplasts also released soluble extracellular carbohydrates: polysaccharides which appeared to be mainly acidic arabinogalactans, and oligosaccharides which were mainly neutral and contained glucose, galactose and mannose. We conclude that regenerating carob protoplasts are a useful system for studying carbohydrate secretion, including mannose‐rich poly‐ and oligosaccharides.     

Hydrolytic fragmentation of seed gums under microwave irradiation

The seed gum solutions of Ipomoea purga, Ipomoea palmata, Ipomoea dasysperma, Cyanaposis tetragonolobus (Guar gum) and Crotolaria medicaginea were microwave (MW) irradiated and their degradation to oligo and monosaccharides was investigated. The gum solutions were fragmented into oligosaccharides/constituent monosaccharides depending upon the length of MW exposure in presence of catalytic amount of mineral acid or even when no acid was used. A mechanism for the microwave induced hydrolytic degradation of the seed gums has been proposed. The MW exposure time required for the partial and complete degradation of the gums was found dependent on the types of the linkages and degree of the branching present in the gums.     

Characterization of the N- and O-linked oligosaccharides in glycoproteins synthesized by Schistosoma mansoni schistosomula

This report describes the structural analyses of the O- and N-linked oligosaccharides contained in glycoproteins synthesized by 48-hr-old Schistosoma mansoni schistosomula. Schistosomula were prepared by mechanical transformation of cercariae and were then incubated in media containing either [2-3H] mannose, [6-3H]glucosamine, or [6-3H]galactose to metabolically radiolabel the oligosaccharide moieties of newly synthesized glycoproteins. Analysis by SDS-polyacrylamide gel electrophoresis and fluorography demonstrated that many glycoproteins were metabolically radiolabeled with the radioactive mannose and glucosamine precursors, whereas few glycoproteins were labeled by the radioactive galactose precursor. Glycopeptide were prepared from the radiolabeled glycoproteins by digestion with pronase and fractionated by chromatography on columns of concanavalin A-Sepharose and pea lectin-agarose. The structures of the oligosaccharide chains in the glycopeptides were analyzed by a variety of techniques. The major O-linked sugars were not bound by concanavalin A-Sepharose and consisted of simple O-linked monosaccharides that were terminal O-linked N-acetylgalactosamine, the minor type, and terminal O-linked N-acetylglucosamine, the major type. The N-linked oligosaccharides were found to consist of high mannose- and complex-type chains. The high mannose-type N-linked chains, which were bound with high affinity by concanavalin A-Sepharose, ranged in size from Man6GlcNAc2 to Man9GlcNAc2. The complex-type chains contained mannose, fucose, N-acetylglucosamine, and N-acetylgalactosamine. No sialic acid was present in any metabolically radiolabeled glycoproteins from schistosomula.     

N-linked high mannose-type oligosaccharides in the protozoa Crithidia fasciculata and Crithidia harmosa contain galactofuranose residues

Incubation of Crithidia fasciculata cells with [U-14C] glucose led to the synthesis of Man-P-dolichol but not of Glc-P-dolichol. The main and largest dolichol-P-P-linked oligosaccharide formed was Man7GlcNAc2 whether labeling was performed in 5 mM sodium pyruvate or 5.5 mM glucose. The protein-linked, endo-beta-N-acetylglucosaminidase H-sensitive oligosaccharides isolated from mature glycoproteins were Man7GlcNAc and Gal1Man6GlcNAc, the latter being a mixture of two isomers. All the galactose residues were present in the furanose configuration, as judged by their extreme lability to acid hydrolysis, by the products obtained upon mild periodate oxidation, and by their sensitivity to beta-galactofuranosidase. Labeling cells for short times or at low temperature yielded a protein-bound, endo-beta-N-acetylglucosaminidase H-sensitive oligosaccharide whose composition was Glc1Man7GlcNAc, of transient existence, and that was mainly labeled in the glucose residue. The latter oligosaccharide was detected on paper chromatography only as a smearing of Man7GlcNAc and Gal1Man6GlcNAc when cells were labeled with [2-3H] mannose, thus indicating that it was only present in minute amounts. Protein-bound endo beta-N-acetylglucosaminidase H-resistant oligosaccharides liberated, upon a mild acid treatment, galactose residues and an unidentified substituent. The treatment rendered the oligosaccharides sensitive to endo beta-N-acetylglucosaminidase H, which liberated Man7GlcNAc and two isomers of Man6GlcNAc. An almost similar mechanism of protein N-glycosylation, including the existence of galactofuranose residues in N-linked oligosaccharides, was found to occur in Crithidia harmosa.     

Carbohydrate structures of HVJ (Sendai virus) glycoproteins

The carbohydrate structures of two membrane glycoproteins (HANA protein and F protein) of HVJ have been determined on materials purified from virions grown in the allantoic sac of embryonated chicken eggs. Both glycoproteins contain fucose, mannose, galactose, and glucosamine but not galactosamine, indicating that their sugar chains are exclusively of the asparagine-linked type. The radioactive oligosaccharide fractions obtained from the two glycoproteins by hydrazinolysis followed by NaB[3H]4 reduction gave quite distinct fractionation patterns after paper electrophoresis. More than 75% of the oligosaccharides from F protein were acidic and separated into at least four components by paper electrophoresis. Only 18% of the oligosaccharide from HANA protein was an acidic single component. These acidic oligosaccharides could not be converted to neutral oligosaccharides by sialidase digestion. Structural studies of the neutral oligosaccharide fractions from HANA and F proteins revealed that both of them are mixtures of a series of high mannose type oligosaccharides and of complex type oligosaccharides with Gal beta 1 leads to (Fuc alpha 1 leads to 3) GlcNAc group in their outer chain moieties.     

Mannosyltransferase activity in calf pancreas microsomes. Formation of 14C-labeled lipid-linked oligosaccharides from GDP-D-[14C]mannose and pancreatic dolichyl beta-D-[14C]mannopyranosyl phosphate.

Calf pancreas microsomes incorporated radioactive D-mannose from GDP-D-[14C]mannose into lipid-bound oligosaccharides extracted with chloroform/methanol/water (10/10/2.5, v/v). Several products, which probably differed in the size of the oligosaccharide moiety, were labeled. These could be partially resolved by thin layer chromatography and DEAE-cellulose chromatography. The labeled lipid-bound oligosaccharides were retained on DEAE-cellulose more strongly than synthetic dolichyl alpha-D-[14C]mannopyranosyl phosphate. They were stable to mild alkali, but labile to acid and hot alkali. Acid treatment yielded a neutral 14C-labeled oligosaccharide fraction which was estimated by gel filtration to have a minimum of 8 monosaccharide residues. Hot alkali treatment yielded a mixture of neutral and acidic 14C-labeled oligosaccharides which could be transformed into neutral products by alkaline phosphatase. The D-[14C]mannose residues were alpha-linked at the nonreducing terminus of the oligosaccharides since they could be removed completely with alpha-mannosidase. Most of the D-[14C]mannose-labeled oligosaccharides were retained on concanavalin A Sepharose and eluted with methyl alpha-D-mannopyranoside. Pancreatic dolichyl beta-D-[14C]mannopyranosyl phosphate incubated with calf pancreas microsomes in the presence of sodium taurocholate was efficiently utilized as donor of alpha-D-mannosyl residues in lipid-bound oligosaccharides. The products formed from dolichyl beta-D-[14C]mannopyranosyl phosphate were identical with those formed from GDP-D-[14C]mannose, and evidence was obtained to show that the dolichyl beta-D-[14C]mannopyranosyl phosphate was serving as donor without prior conversion to GDP-D-[14C]mannose. Transfer of mannose from dolichyl beta-D-[14C]mannopyranosyl phosphate to lipid-bound oligosaccharides took place at a pH optimum of 7.3, whereas transfer to the precipitate containing glycoproteins was greatest at pH 6.0 in Tris/maleate buffer. The addition of divalent cation was not required, but low concentrations of EDTA were extremely inhibitory. The carbohydrate composition of the lipid-bound oligosaccharides of microsomal membranes was investigated by gas-liquid chromatography and by reduction with sodium borotritide. A heterogeneous mixture of oligosaccharides containing N-acetyl-D-glucosamine, D-mannose, and D-glucose varying in proportions from approximately 1/2.5/0.5 to 1/5/1.5 was obtained with glucosamine at the reducing end. Acid treatment of the lipid-bound oligosaccharide fraction yielded dolichyl pyrophosphate, suggesting that at least some of the oligosaccharides were linked to dolichol through a pyrophosphate group.     

An anionic galactomannan polysaccharide gum from a newly-isolated lactose-utilizing bacterium. I. Strain description and gum characterization.

As part of an effort to obtain microorganisms able to produce polysaccharide gums from whey and whey permeate, soil samples from farm fields regularly treated with whey were screened for bacteria able to produce gums from lactose. The most promising organism isolated (ATCC 55046) is a facultative anaerobe, tentatively identified as a new Erwinia species on the basis of biochemical and morphological tests. The organism produces a polysaccharide gum from lactose and other sugars (herein named lactan gum) composed of mannose, galactose, and galacturonic acid with an approximate molar ratio of 5:3:2 and containing no organic acid modifying groups. The weight average molecular weight of the gum is approximately 7 x 10(6). Aqueous solutions of lactan gum exhibit shear-thinning and elastic flow behavior with an estimated power law model flow index of 0.26 at 1% (w/w) gum. The viscosity of aqueous 1% (w/w) lactan gum solutions is stable over a pH range of 2-11, being particularly stable in alkaline environments. Aqueous 1% (w/w) gum solutions at pH 5-11 show excellent thermostability, retaining at least 80% of the original viscosity after being heated to 121 degrees C for 15 min. These flow properties indicate potential industrial applications in food and nonfood products requiring a moderate degree of thickening, wet-end additives and coating agents for paper products, ceramics, detergents, and binders for building materials.     

Isolation of a temperature-sensitive FM3A mutant deficient in asparagine-linked glycosylation by selecting for resistance to tritiated mannose suicide

Protein glycosylation mutants in the mouse mammary carcinoma cell line FM3A were selected for ability to withstand exposure to [2-3H]mannose at 39 degrees C. G258 , one of the mutant cells isolated, has been characterized. G258 cells were temperature-sensitive for cell growth. Moreover, G258 cells showed temperature sensitivity for [3H]mannose incorporation into the TCA-insoluble fraction. To study the biochemical basis of the defect in glycoprotein biosynthesis, the formation of lipid-linked saccharides was examined. The results showed that the formation of lipid-linked oligosaccharides was severely inhibited in G258 cells at 39 degrees C. At 33 degrees C, G258 cells synthesized Glc3Man9GlcNAc2-PP-Dol, the fully assembled lipid-linked oligosaccharides, but at 39 degrees C, G258 cells were able to synthesize merely the smaller lipid-linked oligosaccharides (approximately up to Man3GlcNAc2 -PP-Dol), but were unable to synthesize the larger lipid-linked oligosaccharides.     

The effect of glycoprotein-processing inhibitors on the secretion of glycoproteins by Madin-Darby canine kidney cells

The effects of various glycoprotein-processing inhibitors on the biosynthesis and secretion of N-linked glycoproteins was examined in cultured Madin-Darby canine kidney (MDCK) cells. Since incorporation of [2-3H]mannose into lipid-linked saccharides and into glycoproteins was much greater in phosphate-buffered saline (PBS) than in serum-supplemented basal medium (BME), most experiments were done in PBS. Castanospermine, an inhibitor of glucosidase I, caused the formation of glycoproteins having mostly Glc3Man7-9(GlcNAc)2 structures; deoxymannojirimycin, an inhibitor of mannosidase I, gave mostly glycoproteins with Man9(GlcNAc)2 structures; swainsonine, an inhibitor of mannosidase II, caused the accumulation of hybrid types of oligosaccharides. Castanospermine and swainsonine, either in PBS or in BME medium, had no effect on the incorporation of [2-3H]mannose or [5,6-3H]leucine into the secreted glycoproteins and, in fact, there was some increase in mannose incorporation in their presence. These inhibitors also did not affect mannose incorporation into cellular glycoproteins nor did they affect the biosynthesis as measured by mannose incorporation into lipid-linked saccharides. On the other hand in PBS medium, deoxymannojirimycin, at 25 micrograms/mL, caused a 75% inhibition in mannose incorporation into secreted glycoproteins, but had no effect on the incorporation of [3H]leucine into the secreted glycoproteins. Since deoxymannojirimycin also strongly inhibited mannose incorporation into lipid-linked oligosaccharides in PBS, the decreased amount of radioactivity in the secreted and cellular glycoproteins may reflect the formation of glycoproteins with fewer than normal numbers of oligosaccharide chains, owing to the low levels of oligosaccharide donor. However, in BME medium, there was only slight inhibition of mannose incorporation into lipid-linked saccharides and into cellular and secreted glycoproteins.     

O-oligosaccharidyl-1-amino-1-deoxyalditols as intermediates for fluorescent labelling of oligosaccharides

Reducing monosaccharides were efficiently converted to stable 1-amino-1-deoxyalditols (=glycamines; distinguished from glycosylamines by mass-spectrometry) during incubation at 20 degrees C in saturated aqueous NH(4)HCO(3) containing NaCNBH(3). Potentially useful by-products included a novel, fully-reduced dimer (the corresponding secondary glycamine) and several relatively long-lived, unreduced products. With increasing incubation time, monomers exceeded dimers. Reducing disaccharides and oligosaccharides underwent similar reactions at their reducing termini; the yield of dimers decreased with increasing oligosaccharide M(r). The O-oligosaccharidyl-1-amino-1-deoxyalditols (OADs) obtained by reductive amination of oligosaccharides reacted readily with lissamine rhodamine sulfonyl chloride to yield OAD-sulforhodamine conjugates linked by a stable sulfonamide bond. Conditions for this reaction were optimised (borate buffer, pH9.0-9.5). The highly fluorescent OAD-sulforhodamine products were purified on a C(18) cartridge. They were electrophoretically immobile at pH2.0 and 6.5, and migrated towards the anode in borate buffer, pH9.4. The OAD-sulforhodamines were amenable to TLC and were excellent substrates for enzymic transglycosylation and for glycosylhydrolase action.