The Experts below are selected from a list of 714 Experts worldwide ranked by ideXlab platform
Syed S. Islam - One of the best experts on this subject based on the ideXlab platform.
-
Structural characterization of a Heteroglycan from an edible mushroom Termitomyces heimii.
International journal of biological macromolecules, 2020Co-Authors: Prasenjit Maity, Ipsita K. Sen, Ashis K. Nandi, Manabendra Pattanayak, Dilip K. Manna, Indranil Chakraborty, Sunil K. Bhanja, Atish K. Sahoo, Nibha Gupta, Syed S. IslamAbstract:Abstract A water soluble Heteroglycan (THPS) of an average molecular weight ~1.98 × 105 Da was isolated from the aqueous extract of the fruit bodies of an edible mushroom Termitomyces heimii. Structural characterization of THPS was carried out using acid hydrolysis, methylation analysis, periodate oxidation, Smith degradation and 1D/2D NMR studies. Sugar analysis indicated the presence of glucose, mannose, galactose, and fucose in a molar ratio of nearly 6:2:2:1. The repeating unit of the THPS had a backbone consisting of four (1 → 3)-β- d -glucopyranosyl, one (1 → 6)-β- d -glucopyranosyl, two (1 → 3)-α-D-manopyranosyl, and two (1 → 6)-α-D-galactopyranosyl residues, out of which one (1 → 3)-β- d -glucopyranosyl residue was branched at O-6 position with terminal β- d -glucopyranosyl residue and one (1 → 6)-α-D-galactopyranosyl residue was branched at O-2 position with terminal α-L-fucopyranosyl residue.
-
Studies on structure and antioxidant properties of a Heteroglycan isolated from wild edible mushroom Lentinus sajor-caju.
International journal of biological macromolecules, 2017Co-Authors: Manabendra Pattanayak, Ipsita K. Sen, Prasenjit Maity, Ashis K. Nandi, Dilip K. Manna, Krishnendu Acharya, Surajit Samanta, Sandipta Ghosh, Syed S. IslamAbstract:Abstract A water-soluble Heteroglycan (PS-I) isolated from the aqueous extract of a wild edible mushroom Lentinus sajor-caju showed average molecular weight ∼1.79 × 10 5 Da. The structure of the polysaccharide was determined using chemical and 1D/2D NMR experiments. Acid hydrolysis indicated the presence of d -glucose, d -galactose, d -mannose, and l -fucose in a molar ratio of nearly 4:4:1:1 respectively. The presence of terminal Fuc p , terminal Gal p , (1 → 3)-Glc p , (1 → 6)-Gal p , (1 → 6)-Glc p , (1 → 4,6)-Gal p , and (1 → 2,4)-Man p moieties were established from methylation analysis. The chemical and NMR analyses indicated that the PS-I was a Heteroglycan composed of a repeating unit with backbone chain of three (1 → 6)-α- d -galactopyranosyl residues, two (1 → 6)-β- d -glucopyranosyl residues, one (1 → 4)-α- d -mannopyranosyl residue, and two (1 → 3)-β- d -glucopyranosyl residues where one (1 → 6)-α- d -galactopyranosyl residue was branched at O -4 position with terminal α- l -fucopyranosyl residue and (1 → 4)-α- d -mannopyranosyl residue was branched at O -2 position with terminal α- d -galactopyranosyl residue and the structure was proposed as; The PS-I is a moderate antioxidant compound which showed DPPH radical scavenging activity, hydroxyl radical scavenging activity, ABTS radical scavenging property, reducing power, and ferrous ion chelating ability. Download high-res image (47KB) Download full-size image
-
Heteroglycan of an edible mushroom Pleurotus cystidiosus: Structural characterization and study of biological activities.
International journal of biological macromolecules, 2016Co-Authors: Bibhash C. Panda, Prasenjit Maity, Ashis K. Nandi, Manabendra Pattanayak, Dilip K. Manna, Soumitra Mondal, Satyajit Tripathy, Somenath Roy, Krishnendu Acharya, Syed S. IslamAbstract:Abstract A water soluble Heteroglycan (PCPS) was isolated from the aqueous extract of an edible mushroom Pleurotus cystidiosus. Structural characterization of the Heteroglycan was carried out using total hydrolysis, methylation analysis, periodate oxidation, Smith degradation, and 1D/2D NMR experiments. Sugar analysis indicated the presence of glucose, galactose, and mannose in a molar ratio of nearly 6:2:1 respectively. The chemical and NMR analysis of the PCPS indicated the presence of a repeating unit with a backbone consisting of one unit of (1 → 6)-β- d -glucopyranosyl, two (1 → 3)-β- d -glucopyranosyl, one (1 → 3)-α- d -glucopyranosyl, one (1 → 6)-α- d -glucopyranosyl, and two (1 → 6)-α- d -galactopyranosyl moieties respectively, out of which one (1 → 3)-β- d -glucopyranosyl residue was branched at O -6 with terminal β- d -glucopyranosyl and another (1 → 6)-α- d -galactopyranosyl residue was branched at O -2 with terminal β- d -mannopyranosyl moiety. The polysaccharide was found to exhibit cellular activities at different concentrations (10, 25, 50, 100, 200, 400 μg/mL) and maintained the redox balance as well as reduced lipid per oxidation which protect the cell destruction.
-
Heteroglycan of an edible mushroom termitomyces clypeatus structure elucidation and antioxidant properties
Carbohydrate Research, 2015Co-Authors: Manabendra Pattanayak, Prasenjit Maity, Ashis K. Nandi, Dilip K. Manna, Krishnendu Acharya, Surajit Samanta, Payel Mitra, Syed S. IslamAbstract:Abstract A water-soluble Heteroglycan (PS) of an average molecular weight ∼1.98 ×10 5 Da was isolated from the aqueous extract of an edible mushroom Termitomyces clypeatus (R. Heim). The structure of the polysaccharide (PS) was established using total hydrolysis, methylation analysis, Smith degradation, and 1D/2D NMR experiments. Total hydrolysis indicated the presence of d -glucose, d -galactose, d -mannose, and l -fucose in a molar ratio of 4.10:1.95:1.0:0.95, respectively. The chemical and NMR analysis indicated the presence of a repeating unit with a backbone consisting of one each of the residues (1→3)-α- d -galactopyranosyl, (1→3)-α- d -mannopyranosyl, (1→3)-α- d -glucopyranosyl, (1→3)-β- d -glucopyranosyl, (1→6)-β- d -glucopyranosyl, and (1→6)-α- d -galactopyranosyl, respectively. The (1→3)-α- d -mannopyranosyl residue was found branched at O-2 with terminal α- l -fucopyranosyl moiety and (1→3)-β- d -glucopyranosyl residue was branched at O-6 with terminal α- d -glucopyranosyl residue. The PS exhibited antioxidant properties.
-
Structural characterization of an immunoenhancing Heteroglycan of a hybrid mushroom (pfls1h) of Pleurotus florida and Lentinus squarrosulus (Mont.) Singer.
Carbohydrate Research, 2013Co-Authors: Ipsita K. Sen, Birendra Behera, Tapas K Maiti, Praloy K. Maji, Pijush Mallick, Samir R. Sikdar, Syed S. IslamAbstract:An immunostimulating water-soluble Heteroglycan (PS-II) was isolated from an aqueous extract of the fruit bodies of a hybrid mushroom, pfls1h produced by intergeneric protoplast fusion between Pleurotus florida and Lentinus squarrosulus (Mont.) Singer. Structural characterization of PS-II was carried out using sugar analysis, methylation experiment, periodate oxidation and 1D/2D NMR studies. Sugar analysis indicated the presence of glucose, mannose and galactose in a molar ratio of 1:1:2. Methylation analysis revealed that PS-II was composed of (1→6)- and (1→2,4,6)-α-d-galactopyranosyl, terminal β-d-mannopyranosyl and terminal β-d-glucopyranosyl residues in a relative proportion of approximately 1:1:1:1. On the basis of chemical analysis and NMR studies, the structure of the repeating unit of the Heteroglycan was established to consist of a backbone chain of two (1→6)-α-d-galactopyranosyl residues, one of which is branched at O-2 with terminal β-d-Manp and at O-4 with terminal β-d-Glcp. This Heteroglycan (PS-II) showed in vitro splenocyte, thymocyte and macrophage activations.
Sesselja Omarsdottir - One of the best experts on this subject based on the ideXlab platform.
-
Bioactive effect of sulphated polysaccharides derived from orange-footed sea cucumber (Cucumaria frondosa) toward THP-1 macrophages
Elsevier, 2018Co-Authors: Magdalena M.stefaniak-vidarssona, Sesselja Omarsdottir, Gudrun Marteinsdottir, Gudmundur O. Hreggvidsson, Olafur E. Sigurjonsson, Varsha A.kaleb, María Guðjónsdóttir, Ólafur Friðjónsson, Kristberg KristbergssonAbstract:To access publisher's full text version of this article click on the hyperlink belowAtlantic sea cucumber (Cucumaria frondosa) is a marine invertebrate that occurs naturally in the North Atlantic. Its collagen rich body walls make the sea cucumber an appreciated food source in many countries. The Heteroglycans derived from the cartilage of Atlantic sea cucumbers have shown potential as a source of bioactive compounds, but further investigation is needed to confirm this hypothesis. The objectives of this work were to test the immunomodulating properties of Heteroglycan fractions (FCFs) derived from Atlantic sea cucumbers toward phorbol 12-myristate 13-acetate (PMA) differentiated THP-1 macrophages. Oxygen Radical Absorbance Capacity (ORAC) was determined and cell culture media was collected and analyzed for presence of pro-inflammatory and anti-inflammatory cytokines (TNF-α, IL-6, and IL-10). FCFs toxicity toward macrophages was evaluated by light microscopy and confirmed by XTT proliferation assay. Heteroglycans derived from cartilage of Atlantic sea cucumber showed immunomodulatory activity in THP-1 macrophages. FCF-1, −2, and − 3) at concentrations 0.1–100 µg/mL induced levels of TNF-α, IL-6, and IL-10 proofing their bioactivity towards THP-1 macrophages. However, fractions of FCF-1 and FCF-2 may have induced oxidative stress in the macrophages, which possibly could lead to decreased cellular viability
-
Bioactive effect of sulphated polysaccharides derived from orange-footed sea cucumber (Cucumaria frondosa) toward THP-1 macrophages
Bioactive Carbohydrates and Dietary Fibre, 2017Co-Authors: Magdalena M. Stefaniak-vidarsson, Sesselja Omarsdottir, Varsha Kale, María Gudjónsdóttir, Gudrun Marteinsdottir, Olafur H. Fridjonsson, Gudmundur O. Hreggvidsson, Olafur E. Sigurjonsson, Kristberg KristbergssonAbstract:Abstract Atlantic sea cucumber (Cucumaria frondosa) is a marine invertebrate that occurs naturally in the North Atlantic. Its collagen rich body walls make the sea cucumber an appreciated food source in many countries. The Heteroglycans derived from the cartilage of Atlantic sea cucumbers have shown potential as a source of bioactive compounds, but further investigation is needed to confirm this hypothesis. The objectives of this work were to test the immunomodulating properties of Heteroglycan fractions (FCFs) derived from Atlantic sea cucumbers toward phorbol 12-myristate 13-acetate (PMA) differentiated THP-1 macrophages. Oxygen Radical Absorbance Capacity (ORAC) was determined and cell culture media was collected and analyzed for presence of pro-inflammatory and anti-inflammatory cytokines (TNF-α, IL-6, and IL-10). FCFs toxicity toward macrophages was evaluated by light microscopy and confirmed by XTT proliferation assay. Heteroglycans derived from cartilage of Atlantic sea cucumber showed immunomodulatory activity in THP-1 macrophages. FCF-1, −2, and − 3) at concentrations 0.1–100 µg/mL induced levels of TNF-α, IL-6, and IL-10 proofing their bioactivity towards THP-1 macrophages. However, fractions of FCF-1 and FCF-2 may have induced oxidative stress in the macrophages, which possibly could lead to decreased cellular viability.
-
Supervisors
2014Co-Authors: Sesselja Omarsdottir, Hlynur Árnason, Háskóli Íslands, Snorri Þór SigurðssonAbstract:Isolation and structure determination of a Heteroglycan from whiteworm lichen (Thamnolia subuliformis
-
Structural characterisation of a complex Heteroglycan from the cyanobacterium Nostoc commune
Carbohydrate polymers, 2012Co-Authors: Sophie Jensen, Jens Ø. Duus, Bent O. Petersen, Sesselja Omarsdottir, Berit Smestad Paulsen, Elin S. OlafsdottirAbstract:An alkali-extractable O-methylated ribofuranose-containing Heteroglycan, Nc-5-s, was isolated from wild-growing field colonies of the cyanobacterium Nostoc commune collected in Iceland, using ethanol fractionation and anion-exchange chromatography. The average molecular weight was estimated to be 1500 kDa. Structural characterisation of the Heteroglycan was performed by high-field NMR spectroscopy (1D proton, 2D-COSY, 2D-NOESY, 2D-TOCSY, (1)H (13)C-HSQC, HMBC, H2BC and HSQC-NOESY) as well as monosaccharide analysis after methanolysis by GC and supported by linkage analysis by GC-MS. According to the data obtained, the structure of Nc-5-s is composed of repeating units of 1, 1a, 1b and 2 and 2a in approximate molar ratio of (10:25:50:5:10).
-
Structural characterisation of a new O-methylated Heteroglycan, colleman, from the cyanolichen Collema flaccidum
Carbohydrate Polymers, 2010Co-Authors: J.s.r.e. Jensen, T. Veselinovic, Elin S. Olafsdottir, Jens Ø. Duus, Bent O. Petersen, Sesselja OmarsdottirAbstract:Abstract An alkali-extractable Heteroglycan, colleman, was isolated from the cyanolichen Collema flaccidum, using ethanol fractionation and anion-exchange chromatography. The average molecular weight was estimated to be 360 kDa. Structural characterisation of the Heteroglycan was performed by high-field NMR spectroscopy (1D proton, 2D-COSY, NOESY, 2D-TOCSY, 1H 13C-HSQC, HMBC, H2BC and HSQC-NOESY). According to the data obtained, the structure of colleman is composed of repeating units of A, B, C and D in approximate molar ratio 5:5:2:1;
Tapas K Maiti - One of the best experts on this subject based on the ideXlab platform.
-
Functional Role of a Well Characterized Heteroglycan Isolated from Pleurotus ostreatus Mycelia in Driving Immune Stimulation
2016Co-Authors: K. Sanjana P. Devi, Tapas K MaitiAbstract:Polysaccharides or Heteroglycan isolated from fungal species have attained wide recognition for their immune modulating functions. However, there exists a significant relationship in the structural and functional activity of this molecule. In this commentary, we focus on a well characterized Heteroglycan isolated from the mycelia of Pleurotus ostreatus which have been shown to drive immune stimulation in tumor bearing mice. The Heteroglycan possessed high molecular weight and was primarily composed of glucose, mannose and fucose in a 3:2:1 ratio with major β- linkages in the repeating chain. The molecule also exhibited triple helical conformation in solutions. These immune driving molecules have a significant impact in decreasing the tumor volume in model mice and they are known to play a significant role in the proliferation and activation of lymphocytes in the tumor bearing mice. The physical traits of the Heteroglycan were associated with its immune stimulating ability and such compounds can therefore be utilized as adjuvants in immune based therapies.
-
Molecular Mechanisms Associated With Particulate and Soluble Heteroglycan Mediated Immune Response
Journal of cellular biochemistry, 2015Co-Authors: K. Sanjana P. Devi, Sudip Kumar Ghosh, Dhanesh Krishna, Joyjyoti Das, Tarun Agarwal, Kalpana Kumari, Somnath Maji, Tapas K MaitiAbstract:Immune responses are outcomes of complex molecular machinery which occur inside the cells. Unravelling the cellular mechanisms induced by immune stimulating molecules such as glycans and determining their structure-function relationship are therefore important factors to be assessed. With this viewpoint, the present study identifies the functional receptor binding unit of a well characterized Heteroglycan and also delineates the cellular and molecular processes that are induced upon Heteroglycan binding to specific cell surface receptors in immune cells. The Heteroglycan was acid hydrolysed and it was revealed that 10-30 kDa fractions served as the functional receptor binding unit of the molecule. Increasing the size of 10-30 kDa Heteroglycan showed prominent immune activity. The whole soluble Heteroglycan was also conjugated with hyperbranched dendrimers so as to generate a particulate form of the molecule. Dectin-1 and TLR2 were identified as the major receptors in macrophages that bind to particulate as well as soluble form of the Heteroglycan and subsequently caused downstream signaling molecules such as NF-κβ and MAPK to get activated. High levels of 1L-1β and IL-10 mRNA were observed in particulate Heteroglycan treated macrophages, signifying that increasing the size and availability of the Heteroglycan to its specific receptors is pertinent to its biological functioning. Upregulated expression of PKC and iNOS were also noted in particulate Heteroglycan treated RAW 264.7 cells than the soluble forms. Taken together, our results indicate that biological functions of immunomodulatory Heteroglycan are dependent on their size and molecular weight. J. Cell. Biochem. 117: 1580-1593, 2016. © 2015 Wiley Periodicals, Inc.
-
Assessing the immunomodulatory role of Heteroglycan in a tumor spheroid and macrophage co-culture model system.
Carbohydrate polymers, 2015Co-Authors: K. Sanjana P. Devi, Debasish Mishra, Bibhas Roy, Sudip Kumar Ghosh, Tapas K MaitiAbstract:The therapeutic benefits of glycans have garnered much attention over the last few decades with most studies being reported in 2D cultures or in animal models. The present work is therefore aimed to assess the effects of an immunomodulatory Heteroglycan in a 3D milieu. Briefly, HT29 tumor spheroids were incubated with THP-1 macrophages at 1:1 ratio in a culture medium supplemented with immune stimulants such as Heteroglycans or LPS. Spheroidal distortion, migration of tumor cells from the periphery of the spheroids and 46% of higher macrophage invasiveness was noted in Heteroglycan-treated co-cultures with respect to control cultures. Histological sections of the treated co-cultures revealed the presence of high apoptotic tumor cells in the spheroidal periphery. CD11c and CD68 staining further suggested the predominance of macrophages in the vicinity of the apoptotic tumor cells. Such an in vitro created tissue system may thereby confirm the effectiveness of Heteroglycan in activating the immune cells to exhibit tumor cytotoxic properties.
-
AMPK-mediated crosstalk of Heteroglycan-induced reactive species and autophagic cascade in RAW 264.7 cells
RSC Advances, 2015Co-Authors: K. Sanjana P. Devi, Birendra Behera, Joyjyoti Das, Kalpana Kumari, Prashant Singh, Tapas K MaitiAbstract:Natural polysaccharides are currently being employed for macrophage activation due to their minimal cytotoxicity and side effects. Reactive species like nitric oxide (NO) and reactive oxygen species (ROS), induced by a novel immunostimulatory Heteroglycan were found to regulate the autophagic machinery in RAW 264.7 cells via a feedback mechanism, through AMPK. Heteroglycan-induced autophagy enhanced NO generation while itself being negatively regulated by NO. Concomitantly, intracellular ROS triggered the autophagic machinery which in turn subdued ROS levels indicating a homeostatic mechanism for regulated immune function. This study may help in better understanding of regulated immunostimulation by natural polysaccharides.
-
Structural characterization of an immunoenhancing Heteroglycan of a hybrid mushroom (pfls1h) of Pleurotus florida and Lentinus squarrosulus (Mont.) Singer.
Carbohydrate Research, 2013Co-Authors: Ipsita K. Sen, Birendra Behera, Tapas K Maiti, Praloy K. Maji, Pijush Mallick, Samir R. Sikdar, Syed S. IslamAbstract:An immunostimulating water-soluble Heteroglycan (PS-II) was isolated from an aqueous extract of the fruit bodies of a hybrid mushroom, pfls1h produced by intergeneric protoplast fusion between Pleurotus florida and Lentinus squarrosulus (Mont.) Singer. Structural characterization of PS-II was carried out using sugar analysis, methylation experiment, periodate oxidation and 1D/2D NMR studies. Sugar analysis indicated the presence of glucose, mannose and galactose in a molar ratio of 1:1:2. Methylation analysis revealed that PS-II was composed of (1→6)- and (1→2,4,6)-α-d-galactopyranosyl, terminal β-d-mannopyranosyl and terminal β-d-glucopyranosyl residues in a relative proportion of approximately 1:1:1:1. On the basis of chemical analysis and NMR studies, the structure of the repeating unit of the Heteroglycan was established to consist of a backbone chain of two (1→6)-α-d-galactopyranosyl residues, one of which is branched at O-2 with terminal β-d-Manp and at O-4 with terminal β-d-Glcp. This Heteroglycan (PS-II) showed in vitro splenocyte, thymocyte and macrophage activations.
Martin Steup - One of the best experts on this subject based on the ideXlab platform.
-
a bacterial glucanotransferase can replace the complex maltose metabolism required for starch to sucrose conversion in leaves at night
Journal of Biological Chemistry, 2013Co-Authors: Christian Ruzanski, Martin Steup, Julia B Smirnova, Martin Rejzek, Darrell Cockburn, Henriette L Pedersen, Marilyn J Pike, William G T Willats, Birte Svensson, Oliver EbenhohAbstract:Controlled conversion of leaf starch to sucrose at night is essential for the normal growth of Arabidopsis. The conversion involves the cytosolic metabolism of maltose to hexose phosphates via an unusual, multidomain protein with 4-glucanotransferase activity, DPE2, believed to transfer glucosyl moieties to a complex Heteroglycan prior to their conversion to hexose phosphate via a cytosolic phosphorylase. The significance of this complex pathway is unclear; conversion of maltose to hexose phosphate in bacteria proceeds via a more typical 4-glucanotransferase that does not require a Heteroglycan acceptor. It has recently been suggested that DPE2 generates a heterogeneous series of terminal glucan chains on the Heteroglycan that acts as a “glucosyl buffer” to ensure a constant rate of sucrose synthesis in the leaf at night. Alternatively, DPE2 and/or the Heteroglycan may have specific properties important for their function in the plant. To distinguish between these ideas, we compared the properties of DPE2 with those of the Escherichia coli glucanotransferase MalQ. We found that MalQ cannot use the plant Heteroglycan as an acceptor for glucosyl transfer. However, experimental and modeling approaches suggested that it can potentially generate a glucosyl buffer between maltose and hexose phosphate because, unlike DPE2, it can generate polydisperse malto-oligosaccharides from maltose. Consistent with this suggestion, MalQ is capable of restoring an essentially wild-type phenotype when expressed in mutant Arabidopsis plants lacking DPE2. In light of these findings, we discuss the possible evolutionary origins of the complex DPE2-Heteroglycan pathway.
-
Starch-related cytosolic Heteroglycans in roots from Arabidopsis thaliana.
Journal of plant physiology, 2011Co-Authors: Irina Malinova, Martin Steup, Joerg FettkeAbstract:Abstract Both photoautotrophic and heterotrophic plant cells are capable of accumulating starch inside the plastid. However, depending on the metabolic state of the respective cell the starch-related carbon fluxes are different. The vast majority of the transitory starch biosynthesis relies on the hexose phosphate pools derived from the reductive pentose phosphate cycle and, therefore, is restricted to ongoing photosynthesis. Transitory starch is usually degraded in the subsequent dark period and mainly results in the formation of neutral sugars, such as glucose and maltose, that both are exported into the cytosol. The cytosolic metabolism of the two carbohydrates includes reversible glucosyl transfer reactions to a Heteroglycan that are mediated by two glucosyl transferases, DPE2 and PHS2 (or, in all other species, Pho2). In heterotrophic cells, accumulation of starch mostly depends on the long distance transport of reduced carbon compounds from source to sink organs and, therefore, includes as an essential step the import of carbohydrates from the cytosol into the starch forming plastids. In this communication, we focus on starch metabolism in heterotrophic tissues from Arabidopsis thaliana wild type plants (and in various starch-related mutants as well). By using hydroponically grown A. thaliana plants, we were able to analyse starch-related biochemical processes in leaves and roots from the same plants. Within the roots we determined starch levels and the morphology of native starch granules. Cytosolic and apoplastic Heteroglycans were analysed in roots and compared with those from leaves of the same plants. A. thaliana mutants lacking functional enzymes either inside the plastid (such as phosphoglucomutase) or in the cytosol (disproportionating isoenzyme 2 or the phosphorylase isozyme, PHS2) were included in this study. In roots and leaves from the three mutants (and from the respective wild type organ as well), starch and Heteroglycans as well as enzyme patterns were analysed.
-
Identification of a novel Heteroglycan-interacting protein, HIP 1.3, from Arabidopsis thaliana
Journal of plant physiology, 2010Co-Authors: Joerg Fettke, Adriano Nunes-nesi, Alisdair R. Fernie, Martin SteupAbstract:Abstract Plastidial degradation of transitory starch yields mainly maltose and glucose. Following the export into the cytosol, maltose acts as donor for a glucosyl transfer to cytosolic Heteroglycans as mediated by a cytosolic transglucosidase (DPE2; EC 2.4.1.25) and the second glucosyl residue is liberated as glucose. The cytosolic phosphorylase (Pho2/PHS2; EC 2.4.1.1) also interacts with Heteroglycans using the same intramolecular sites as DPE2. Thus, the two glucosyl transferases interconnect the cytosolic pools of glucose and glucose 1-phosphate. Due to the complex monosaccharide pattern, other Heteroglycan-interacting proteins (HIPs) are expected to exist. Identification of those proteins was approached by using two types of affinity chromatography. Heteroglycans from leaves of Arabidopsis thaliana (Col-0) covalently bound to Sepharose served as ligands that were reacted with a complex mixture of buffer-soluble proteins from Arabidopsis leaves. Binding proteins were eluted by sodium chloride. For identification, SDS-PAGE, tryptic digestion and MALDI-TOF analyses were applied. A strongly interacting polypeptide (approximately 40 kDa; designated as HIP1.3) was observed as product of locus At1g09340. Arabidopsis mutants deficient in HIP1.3 were reduced in growth and contained Heteroglycans displaying an altered monosaccharide pattern. Wild type plants express HIP1.3 most strongly in leaves. As revealed by immuno fluorescence, HIP1.3 is located in the cytosol of mesophyll cells but mostly associated with the cytosolic surface of the chloroplast envelope membranes. In an HIP1.3-deficient mutant the immunosignal was undetectable. Metabolic profiles from leaves of this mutant and wild type plants as well were determined by GC–MS. As compared to the wild type control, more than ten metabolites, such as ascorbic acid, fructose, fructose bisphosphate, glucose, glycine, were elevated in darkness but decreased in the light. Although the biochemical function of HIP1.3 has not yet been elucidated, it is likely to possess an important function in the central carbon metabolism of higher plants.
-
Cytosolic Heteroglycans in photoautotrophic and in heterotrophic plant cells.
Phytochemistry, 2009Co-Authors: Joerg Fettke, Irina Malinova, Nora Eckermann, Martin SteupAbstract:In plants several 'starch-related' enzymes exist as plastid- and cytosol-specific isoforms and in some cases the extraplastidial isoforms represent the majority of the enzyme activity. Due to the compartmentation of the plant cells, these extraplastidial isozymes have no access to the plastidial starch granules and, therefore, their in vivo function remained enigmatic. Recently, cytosolic Heteroglycans have been identified that possess a complex pattern of the monomer composition and glycosidic bonds. The glycans act both as acceptors and donors for cytosolic glucosyl transferases. In autotrophic tissues the Heteroglycans are essential for the nocturnal starch-sucrose conversion. In this review we summarize the current knowledge of these glycans, their interaction with glucosyl transferases and their possible cellular functions. We include data on the Heteroglycans in heterotrophic plant tissues and discuss their role in intracellular carbon fluxes that originate from externally supplied carbohydrates.
-
Alterations in Cytosolic Glucose-Phosphate Metabolism Affect Structural Features and Biochemical Properties of Starch-Related Heteroglycans
Plant physiology, 2008Co-Authors: Joerg Fettke, Adriano Nunes-nesi, Alisdair R. Fernie, Jessica Alpers, Michal Szkop, Martin SteupAbstract:The cytosolic pools of glucose-1-phosphate (Glc-1-P) and glucose-6-phosphate are essential intermediates in several biosynthetic paths, including the formation of sucrose and cell wall constituents, and they are also linked to the cytosolic starch-related Heteroglycans. In this work, structural features and biochemical properties of starch-related Heteroglycans were analyzed as affected by the cytosolic glucose monophosphate metabolism using both source and sink organs from wild-type and various transgenic potato (Solanum tuberosum) plants. In leaves, increased levels of the cytosolic phosphoglucomutase (cPGM) did affect the cytosolic Heteroglycans, as both the glucosyl content and the size distribution were diminished. By contrast, underexpression of cPGM resulted in an unchanged size distribution and an unaltered or even increased glucosyl content of the Heteroglycans. Heteroglycans prepared from potato tubers were found to be similar to those from leaves but were not significantly affected by the level of cPGM activity. However, external glucose or Glc-1-P exerted entirely different effects on the cytosolic Heteroglycans when added to tuber discs. Glucose was directed mainly toward starch and cell wall material, but incorporation into the constituents of the cytosolic Heteroglycans was very low and roughly reflected the relative monomeric abundance. By contrast, Glc-1-P was selectively taken up by the tuber discs and resulted in a fast increase in the glucosyl content of the Heteroglycans that quantitatively reflected the level of the cytosolic phosphorylase activity. Based on 14C labeling experiments, we propose that in the cytosol, glucose and Glc-1-P are metabolized by largely separated paths.
Elin S. Olafsdottir - One of the best experts on this subject based on the ideXlab platform.
-
Structural characterisation of a complex Heteroglycan from the cyanobacterium Nostoc commune
Carbohydrate polymers, 2012Co-Authors: Sophie Jensen, Jens Ø. Duus, Bent O. Petersen, Sesselja Omarsdottir, Berit Smestad Paulsen, Elin S. OlafsdottirAbstract:An alkali-extractable O-methylated ribofuranose-containing Heteroglycan, Nc-5-s, was isolated from wild-growing field colonies of the cyanobacterium Nostoc commune collected in Iceland, using ethanol fractionation and anion-exchange chromatography. The average molecular weight was estimated to be 1500 kDa. Structural characterisation of the Heteroglycan was performed by high-field NMR spectroscopy (1D proton, 2D-COSY, 2D-NOESY, 2D-TOCSY, (1)H (13)C-HSQC, HMBC, H2BC and HSQC-NOESY) as well as monosaccharide analysis after methanolysis by GC and supported by linkage analysis by GC-MS. According to the data obtained, the structure of Nc-5-s is composed of repeating units of 1, 1a, 1b and 2 and 2a in approximate molar ratio of (10:25:50:5:10).
-
Structural characterisation of a new O-methylated Heteroglycan, colleman, from the cyanolichen Collema flaccidum
Carbohydrate Polymers, 2010Co-Authors: J.s.r.e. Jensen, T. Veselinovic, Elin S. Olafsdottir, Jens Ø. Duus, Bent O. Petersen, Sesselja OmarsdottirAbstract:Abstract An alkali-extractable Heteroglycan, colleman, was isolated from the cyanolichen Collema flaccidum, using ethanol fractionation and anion-exchange chromatography. The average molecular weight was estimated to be 360 kDa. Structural characterisation of the Heteroglycan was performed by high-field NMR spectroscopy (1D proton, 2D-COSY, NOESY, 2D-TOCSY, 1H 13C-HSQC, HMBC, H2BC and HSQC-NOESY). According to the data obtained, the structure of colleman is composed of repeating units of A, B, C and D in approximate molar ratio 5:5:2:1;
-
Immunomodulating effects of lichen-derived polysaccharides on monocyte-derived dendritic cells.
International immunopharmacology, 2006Co-Authors: Sesselja Omarsdottir, Elin S. Olafsdottir, Jona FreysdottirAbstract:Many naturally occurring polysaccharides from fungi and lichens have been found to have immunomodulating activity. However, the majority of these studies have focused on their effects on the innate arm of the immune system. Although dendritic cells (DCs) belong to the innate immune system, they play an important role as a bridge between the innate and the adaptive immune response. In this study, the effects of 11 chromatographically purified and well-characterised lichen polysaccharides (of different structural types) on the maturation of DCs were tested by analysing the secretion of IL-12p40 and IL-10 by human monocyte-derived dendritic cells in vitro. Four of the polysaccharides upregulated IL-10 secretion by the dendritic cells, as compared with unstimulated cells, the β-glucans lichenan and Ths-2 and the Heteroglycans Pc-4 and thamnolan. IL-12p40 secretion was significantly upregulated by the β-glucan lichenan and the Heteroglycans Pc-2, Pc-4, thamnolan and Ths-4, while the mature dendritic cells stimulated with the Heteroglycan Pc-1 secreted significantly less IL-12p40 than the unstimulated cells. Proportional index (PI) was used to determine the relationship between the IL-12p40 and IL-10 secretion. The PI of all the β-glucans, i.e. lichenan, pustulan and Ths-2, and the Heteroglycan thamnolan was significantly lower than the PI observed for the unstimulated cells, which was mainly due to increased IL-10 secretion. Therefore, these polysaccharides could be considered suitable candidates in tolerance and anti-inflammatory studies, as IL-10 is one of the major cytokines involved in tolerance and anti-inflammatory responses.
-
Effects of lichen Heteroglycans on proliferation and IL-10 secretion by rat spleen cells and IL-10 and TNF-alpha secretion by rat peritoneal macrophages in vitro.
Phytomedicine : international journal of phytotherapy and phytopharmacology, 2005Co-Authors: Sesselja Omarsdottir, J Freysdottir, H Barsett, B Smestad Paulsen, Elin S. OlafsdottirAbstract:Four polysaccharides Pc-1, Pc-2, Pc-3 and Pc-4 were isolated from water and alkali extracts of the lichen Peltigera canina using ethanol fractionation, gel filtration and preparative HP-GPC. The monosaccharide composition was determined by methanolysis and GC and showed mannose and galactose as the predominating structural units. The mean M(r) was determined by HP-GPC. The Heteroglycans were tested for in vitro immunomodulating activities and showed mitogenic activity in rat spleen cell proliferation assay and stimulated IL-10 secretion. In rat peritoneal macrophages, the Heteroglycans stimulated TNF-alpha secretion, but not IL-10 secretion. These results indicate that the polysaccharides influence cells of the immune system both from the innate and the adaptive systems.
-
Polysaccharides from lichens : Structural characteristics and biological activity
Planta medica, 2001Co-Authors: Elin S. Olafsdottir, K. IngólfsdóttirAbstract:Lichens have been used for medicinal purposes throughout the ages, and beneficial claims have to some extent been correlated with their polysaccharide content. Of 13,500 lichen species growing worldwide, less than 100 species have been investigated for polysaccharide content. Lichen polysaccharides are mainly of three different structural types: beta-glucans, alpha-glucans, and galactomannans. In addition, a few complex Heteroglycans have recently been described, such as thamnolan, a water-soluble, immunologically active Heteroglycan with a novel rhamnopyranosylgalactofuranan type of structure. A number of investigations have been carried out on biological effects of lichen polysaccharides, most notably antitumour, immunomodulating, antiviral, and memory-enhancing effects. The current review summarizes present knowledge on the structural characteristics and biological activity of lichen polysaccrides.