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1. (Article ID: 6192)
 
Rüdiger H, Siebert H-C, Solis D, Jiménez-Barbero J, Romero A, von der Lieth C-W, Diaz-Mariño T, Gabius H-J
Medicinal chemistry based on the sugar code: fundamentals of lectinology and experimental strategies with lectins as targets
Current Medicinal Chemistry 7(4) (2000) 389-416
 

Theoretical calculations reveal that oligosaccharides are second to no other class of biochemical oligomery in terms of coding capacity. As integral part of cellular glycoconjugates they can serve as recognitive units for receptors (lectins). Having first been detected in plants, lectins are present ubiquitously. Remarkably for this field, they serve as bacterial and viral adhesins. Following a description of these branches of lectinology to illustrate history, current status and potential for medicinal chemistry, we document that lectins are involved in a wide variety of biochemical processes including intra- and intercellular glycoconjugate trafficking, initiation of signal transduction affecting e. g. growth regulation and cell adhesion in animals. It is thus justified to compare crucial carbohydrate epitopes with the postal code ensuring correct mail routing and delivery. In view of the functional relevance of lectins the design of high-affinity reagents to occupy their carbohydrate recognition domains offers the perspective for an attractive source of new drugs. Their applications can be supposed to encompass the use as cell-type-selective determinant for targeted drug delivery and as blocking devices in anti-adhesion therapy during infections and inflammatory disease. To master the task of devising custom-made glycans/glycomimetics for this purpose, the individual enthalpic and entropic contributions in the molecular rendezvous between the sugar receptor under scrutiny and its ligand in the presence of solvent molecules undergoing positional rearrangements need to be understood and rationally exploited. As remunerative means to this end, cleverly orchestrated deployment of a panel of methods is essential. Concerning the carbohydrate ligand, its topological parameters and flexibility are assessed by the combination of computer-assisted molecular-mechanics and molecular-dynamics calculations and NMR-spectroscopic measurements. In the presence of the receptor, the latter technique will provide insights into conformational aspects of the bound ligand and into spatial vicinity of the ligand to distinct side chains of amino acids establishing the binding site in solution. Also in solution, the hydrogen-bonding pattern in the complex can be mapped with monodeoxy and monofluoro derivatives of the oligosaccharide. Together with X-ray crystallographic and microcalorimetric studies the limits of a feasible affinity enhancement can be systematically probed. With galactoside-binding lectins as instructive mo del, recent progress in this area of drug design will be documented, emphasizing the general applicability of the outlined interdisciplinary approach.

Molecular mechanics, Rhizobium meliloti, lectinology, lectins as targets, computer assisted, NMR spectoscopic, crystallographic elucidation, sugar code, chemioal tailoring, phosphodiester backbone, microheterogeneity of glycan, monomer variability, N acetylneuramicinic, transgenic pollen, nitrogen enriched nutrients, non agglutinating ricin, hydrophobic molecules, phytopathogenic fungus, phosphomannose mutase, B bearing individuals, anti adhesion therapy, NMR spectrum, parenchymal host cells

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2. (Article ID: 6969)
 
Yamaguchi T, Ito Y, Shibuya N
Oligosaccharide elicitors and their receptors for plant defense responses
Trends in Glycoscience and Glycotechnology 12 (2000) 113-120
 

N-Acetylchitooligosaccharides (oligochitin, chitin oligosaccharides) of a specific size can act as potent elicitor signals for suspension-cultured rice cells as well as various plant cells which include many monocots and some dicots. We recently isolated and characterized a highly elicitor-active glucopentaose from the cell wall P-Glucan from rice blast disease fungus. The results indicated that rice and soybean cells recognize different structural units of fugal glucans as elicitor signals. Because this elicitor treatment can induce many defense reactions, it has been serving as an excellent model system for the study of the signal transduction cascade leading to the activation of defense-related genes. It is critically important to identify and characterize the receptor molecules which perceive the elicitor signal to clarify the whole signal transduction cascade. A 75 kDa chitin oligosaccharide binding protein in the plasma membrane of suspension-cultured rice cells was identified as a putative receptor for the elicitor and purified. Recent studies on the structure and function of the binding proteins for these oligosaccharide elicitors will provide a clue to understanding how these elicitors are perceived and transduced in rice and other plant cells and also how such recognition systems have evolved.

receptor, signal transduction, elicitor

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3. (Article ID: 8850)
 
Matsuzawa T, Watanabe M, Nakamichi Y, Fujimoto Z, Yaoi K
Crystal structure and substrate recognition mechanism of Aspergillus oryzae isoprimeverose-producing enzyme
Journal of Structural Biology 205(1) (2019) 84-90
 

Isoprimeverose-producing enzymes (IPases) release isoprimeverose (α-D-xylopyranosyl-(1→6)-D-glucopyranose) from the non-reducing end of xyloglucan oligosaccharides. Aspergillus oryzae IPase (IpeA) is classified as a member of the glycoside hydrolase family 3 (GH3); however, it has unusual substrate specificity compared with other GH3 enzymes. Xylopyranosyl branching at the non-reducing ends of xyloglucan oligosaccharides is vital for IpeA activity. We solved the crystal structure of IpeA with isoprimeverose at 2.4 Å resolution, showing that the structure of IpeA formed a dimer and was composed of three domains: an N-terminal (β/α)8 TIM-barrel domain, α/β/α sandwich fold domain, and a C-terminal fibronectin-like domain. The catalytic TIM-barrel domain possessed a catalytic nucleophile (Asp300) and acid/base (Glu524) residues. Interestingly, we found that the cavity of the active site of IpeA was larger than that of other GH3 enzymes, and subsite -1' played an important role in its activity. The glucopyranosyl and xylopyranosyl residues of isoprimeverose were located at subsites -1 and -1', respectively. Gln58 and Tyr89 contributed to the interaction with the xylopyranosyl residue of isoprimeverose through hydrogen bonding and stacking effects, respectively. Our findings provide new insights into the substrate recognition of GH3 enzymes.

Aspergillus oryzae, isoprimeverose, xyloglucan, glycoside hydrolase family 3, hemicellulose

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4. (Article ID: 8851)
 
Matsuzawa T, Watanabe M, Kameda T, Kameyama A, Yaoi K
Cooperation between β-galactosidase and an isoprimeverose-producing oligoxyloglucan hydrolase is key for xyloglucan degradation in Aspergillus oryzae
FEBS Journal 286(16) (2019) 3182-3193
 

The galactosylation of xyloglucan blocks many of the enzymatic processes targeting this oligosaccharide. We found that the expression of a gene encoding Aspergillus oryzae β-galactosidase (LacA) is induced in the presence of xyloglucan oligosaccharides. With detailed analyses of the substrate specificity of purified recombinant LacA, we show that LacA cleaves galactopyranosyl residues from xyloglucan oligosaccharides, but not from xyloglucan polysaccharide, and plays a vital role in xyloglucan degradation. LacA acts cooperatively with the isoprimeverose-producing oligoxyloglucan hydrolase IpeA to hydrolyze xyloglucan oligosaccharides. Galactosylation of the xylopyranosyl side chain at the nonreducing end of oligoxyloglucan saccharides completely abolishes IpeA activity while LacA efficiently removes the galactopyranosyl residue. Conversely, an isoprimeverose unit at the nonreducing end of the main chain of xyloglucan oligosaccharides blocks LacA activity, while IpeA can still remove the isoprimeverose moiety. This is the first study reporting the cooperative action of β-galactosidase and isoprimeverose-producing oligoxyloglucan hydrolase on xyloglucan oligosaccharide degradation. Our findings shed light on the true role of LacA and the enzymatic coordination between β-galactosidase and other hydrolases on xyloglucan degradation.

oligosaccharide, β-Galactosidase, Aspergillus oryzae, xyloglucan, isoprimeverose-producing oligoxyloglucan hydrolase

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5. (Article ID: 11068)
 
Dormann P, Benning C
Galactolipids rule in seed plants
Trends in Plant Science 7(3) (2002) 112-118
 

Chloroplast membranes contain high levels of the galactolipids monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG). The isolation of the genes involved in the biosynthesis of MGDG and DGDG, and the identification of galactolipid-deficient Arabidopsis mutants has greatly facilitated the analysis of galactolipid biosynthesis and function. Galactolipids are found in X-ray structures of photosynthetic complexes, suggesting a direct role in photosynthesis. Furthermore, galactolipids can substitute for phospholipids, as suggested by increases in the galactolipid:phospholipid ratio after phosphate deprivation. The ratio of MGDG to DGDG is also crucial for the physical phase of thylakoid membranes and might be regulated

glycosyltransferase, membrane, phospholipid, Arabidopsis, chloroplast, thylakoid, monogalactosyldiacylglycerol, digalactosyldiacylglycerol, UDP-galactose, phosphate nutrition

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6. (Article ID: 11294)
 
Mazeau K, Perez S
The preferred conformations of the four oligomeric fragments of Rhamnogalacturonan II
Carbohydrate Research 311(4) (1998) 203-217
 

Rhamnogalacturonan II (RG-II) is a structurally complex pectic mega-oligosaccharide that is released enzymatically from the primary cell wall of higher plants. RG-II contains 28 monosaccharide units (MW approximately equal to 6 KDa) which belong to 12 different families of glycosyl residues, including very unusual ones such as Kdo, Dha, aceric acid, and apiose. Eighteen different disaccharide segments can be identified, and so far the primary structure has not yet been determined. These monomeric units are arranged into four structurally well-defined oligosaccharide side chains, linked to a pectic backbone made up of 1,4-linked alpha-D-galactosyluronic acid residues. The specific attachment sites of these four side-chains on the pectic backbone remains to be elucidated. The present work presents a three-dimensional database of all the monosaccharide and disaccharide components of RG-II. The conformational behavior of D-Apif and L-AceAf monosaccharide has been assessed through computations performed with the molecular mechanics program MM3 using the flexible residue approach. For each furanosyl residue, energies of various envelope and twist conformers were systematically calculated as a function of the puckering parameters Q and phi. Energy minima are observed in both the Northern and Southern zones of the conformational wheel of each monosaccharide. As for the constituting segments, the conformational behaviour of 18 different disaccharides was evaluated using the flexible residue procedure of the MM3 molecular mechanics procedure. For each disaccharide, the adiabatic energy surface, along with the locations of the local energy minima and drawings of the conformations of each local minimum located in the energy maps have been established. The geometries of the minima and the potential energy surfaces of the different fragments were included in the database of the POLYS, a program for building oligo and polysaccharides. All these results were used for the generation, prior to a complete optimization, of the complete structure of each fragment of RG-II. It is shown that both A and B fragments are very flexible about the two sidechain glycosidic linkages which are closest to the backbone. The remaining part of the sidechain is rigid for the heavily branched A fragment, it is flexible for the more linear B fragment. The lowest energy conformer of each fragment results in good exposure of the hydroxyl groups of the apiosyl residues. Some possible implications of these features in boron complexation are presented.

Kdo, DHA, Rhamnogalacturonan II, aceric acid, apiose conformation, MM3, furanosyl, puckering parameters

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7. (Article ID: 11301)
 
Schindler TM
The new view of the primary cell wall
Journal of Plant Nutrition and Soil Science = Zeitschrift Für Pflanzenernährung Und Bodenkunde 161(5) (1998) 499-508
 

The plant cell wall is essential to almost every aspect of plant life. The cell wall is a dynamic and highly ordered complex of polysaccharides, structural proteins and phenolics. The introduction of new techniques in the study of cell-wall architecture, namely the availability of antibodies to cell wall components, new methods in electron microscopy, application of physico-chemical techniques like FTIR and NMR as well as refined biochemical analyses have substantially changed our conception of the cell wall. The extracellular matrix is no longer understood as a static, mainly covalently cross-linked macromolecular structure but as a flexible, developmentally regulated network that is largely based on non-covalent interactions. Three principally independent but interacting networks that form local microdomains can be distinguished: The cellulose-microfibril-xyloglucan network, the network of pectins and the network of structural cell wall proteins. This review summarizes the current ideas about the architecture and biochemical composition of primary cell walls.

polysaccharides, nuclear magnetic resonance, Arabidopsis thaliana, arabinogalactan proteins, plant extracellular matrix, auxin mediated growth, maize coleoptiles, suspension cultures, cross linking, carrot cells

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8. (Article ID: 11302)
 
Rayon C, Lerouge P, Faye L
The protein N-glycosylation in plants
Journal of Experimental Botany 49(326) (1998) 1463–1472
 

In plants, most proteins of the extracellular compartment and the endomembrane system are glycosylated by N-linked oligosaccharides. The N-glycosylation of proteins has a great impact both on their physicochemical properties and on their biological functions. Over the last ten years, a number of laboratories have contributed considerably to the understanding of the structure, the biosynthesis and the function of plant N-linked glycans. In this review, data on this domain will be summarized and the recent results on the N-glycosylation of a vacuolar lectin, the bean phytohaemagglutinin (PHA) will also be included. This PHA, used as a model glycoprotein, was expressed in different plant systems and the N-glycosylation patterns of different recombinant PHA were compared. In addition to this study on plant-specific glycosylation, the same model glycoprotein was used to investigate whether or not N-glycosylation and N-glycan maturation is organ-specific in plants.

N-Linked oligosaccharide, biosynthesis and function, phytohaemagglutinin

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9. (Article ID: 11303)
 
Lerouge P, Rayon C, Gomord V, Faye L
N-glycoprotein biosynthesis in plants: recent developments and future trends
Plant Molecular Biology 38(1-2) (1998) 31-48
 

N-glycosylation is a major modification of proteins in plant cells. This process starts in the endoplasmic reticulum by the co-translational transfer of a precursor oligosaccharide to specific asparagine residues of the nascent polypeptide chain. Processing of this oligosaccharide into high-mannose-type, paucimannosidic-type, hybrid-type or complex-type N-glycans occurs in the secretory pathway as the glycoprotein moves from the endoplasmic reticulum to its final destination. At the end of their maturation, some plant N-glycans have typical structures that differ from those found in their mammalian counterpart by the absence of sialic acid and the presence of beta(1,2)-xylose and alpha(1,3)-fucose residues. Glycosidases and glycosyltransferases that respectively catalyse the stepwise trimming and addition of sugar residues are generally considered as working in a co-ordinated and highly ordered fashion to form mature N-glycans. On the basis of this assembly line concept, fast progress is currently made by using N-linked glycan structures as milestones of the intracellular transport of proteins along the plant secretory pathway. Further developments of this approach will need to more precisely define the topological distribution of glycosyltransferases within a plant Golgi stack. In contrast with their acknowledged role in the targeting of lysosomal hydrolases in mammalian cells, N-glycans have no specific function in the transport of glycoproteins into the plant vacuole. However, the presence of N-glycans, regardless of their structures, is necessary for an efficient secretion of plant glycoproteins. In the biotechnology field, transgenic plants are rapidly emerging as an important system for the production of recombinant glycoproteins intended for therapeutic purposes, which is a strong motivation to speed up research in plant glycobiology. In this regard, the potential and limits of plant cells as a factory for the production of mammalian glycoproteins will be illustrated.

plant, Recombinant Proteins, Arabidopsis thaliana, N-glycosylation

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10. (Article ID: 11304)
 
Ovodov IS
Polysaccharides of flower plants: structure and physiological activity
Bioorganicheskaya Khimia = Bioorganic Chemistry [Russian] 24(7) (1998) 483-501
 

The results of studies on the chemical structure and physiological activity of phanerogam polysaccharides, accumulated within the last two decades, are reviewed. Three types of polysaccharides are considered: rhamnogalacturonans (pectins and related gums and mucilages, type A), acidic arabinogalactans (mainly plant mucilages, gums, and some hemicelluloses, type B), and neutral glucans and heteroglycans (reserve polysaccharides, type C). Various physiological activities of these plant polysaccharides are discussed, with particular emphasis being placed on their immunomodulatory action. The data available on the relationship between chemical structure and physiological activity of plant polysaccharides are considered. Information on the medicinal use of some plants containing physiologically active polysaccharides is presented.

полисахариды растений, пектины, арабино-3, 6-галактаны, а-1, 4-глюканы, физиологическая активность, иммуномодуляторы

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11. (Article ID: 11305)
 
Ceriotti A, Duranti M, Bollini R
Effects of N-glycosylation on the folding and structure of plant proteins
Journal of Experimental Botany 249(324) (1998) 1091–1103
 

The synthesis of many of the proteins that are translocated into the endoplasmic reticulum is accompanied by the co-translational attachment of preformed oligosaccharide chains to certain Asn residues. These glycans can play a variety of roles in the mature proteins, including the one of stabilizing the protein and protecting the polypeptide backbone from the action of proteases. In addition, they can have a crucial function during the process of polypeptide folding, when aggregation with other proteins would hamper the acquisition of the native conformation. Their influence on protein folding can be direct, or mediated by interactions with endoplasmic reticulum-located molecular chaperones. The elucidation of the mechanisms that govern glycoprotein folding in the plant endoplasmic reticulum should contribute to the understanding of how much plant cells rely on glycan chains to achieve the efficient folding of many proteins under diverse environmental conditions. In addition, a better knowledge of the level of conservation of the in vivo folding mechanisms will be important for the exploitation of plant cells in the production of heterologous glycoproteins.

endoplasmic reticulum, calnexin, calreticulin, glucose trimming, glycoprotein stability

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12. (Article ID: 11394)
 
Deng SJ, Yu B, Hui YZ
A facile synthetic approach to a group of structurally typical diosgenyl saponins
Tetrahedron Letters 39(36) (1998) 6511-6514
 

Five new steroids, the cholest-4-ene-3,22-diones : tumacone A (1), tumacone B (2), tumacoside A (3), tumacoside B (4), and a furostenone: tumaquenone (5), besides diosgenone (6), were isolated from the aerial parts of Solanum nudum. Their structures were determined by 2D NMR, MS analyses and chemical correlations. Steroid 3 and 5 displayed in vitro antimalarial activity against a Plasmodium falciparum chloroquine-resistant FCB-1 strain (IC50 27 and 16 mu M). The observed stereodependent cyclization into spiroketals of two 16-O isomers is discussed.

antimalarial, steroids, Solanum nudum, cholest-4-en-3, 22-dione, tumacones A and B, tumacosides A and B, tumaquenone, stereodependent cyclization

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13. (Article ID: 11426)
 
Vlietinck AJ, De Bruyne T, Apers S, Pieters LA
Plant-derived leading compounds for chemotherapy of human immunodeficiency virus (HIV) infection
Planta Medica 64(2) (1998) 97-109
 

Many compounds of plant origin have been identified that inhibit different stages in the replication cycle of human immunodeficiency virus (HIV): 1) virus adsorption: chromone alkaloids (schumannificine), isoquinoline alkaloids (michellamines), sulphated polysaccharides and polyphenolics, flavonoids, coumarins (glycocoumarin, licopyranocoumarin) phenolics (caffeic acid derivatives, galloyl acid derivatives, catechinic acid derivatives), tannins and triterpenes (glycyrrhizin and analogues, soyasaponin and analogues); 2) virus-cell fusion: lectins (mannose- and N-acetylglucosamine-specific) and triterpenes (betulinic acid and analogues); 3) reverse transcription; alkaloids (benzophenanthridines, protoberberines, isoquinolines, quinolines), coumarins (calanolides and analogues), flavonoids, phloroglucinols, lactones (protolichesterinic acid), tannins, iridoids (fulvoplumierin) and triterpenes; 4) integration: coumarins (3-substituted-4-hydroxycoumarins), depsidones, O-caffeoyl derivatives, lignans (arctigenin and analogues) and phenolics (curcumin); 5) translation: single chain ribosome inactivating proteins (SCRIP's); 6) proteolytic cleavage (protease inhibition): saponins (ursolic and maslinic acids), xanthones (mangostin and analogues) and coumarins; 7) glycosylation: alkaloids including indolizidines (castanospermine and analogues), piperidines (1-deoxynojirimicin and analogues) and pyrrolizidines (australine and analogues); 8) assembly/release: naphthodianthrones (hypericin and pseudohypericin), photosensitisers (terthiophenes and furoisocoumarins) and phospholipids. The target of action of several anti-HIV substances including alkaloids (O-demethyl-buchenavianine, papaverine), polysaccharides (acemannan), lignans (intheriotherins, schisantherin), phenolics (gossypol, lignins, catechol dimers such as peltatols, naphthoquinones such as conocurvone) and saponins (celasdin B, Gleditsia and Gymnocladus saponins), has not been elucidated or does not fit in the proposed scheme. Only a very few of these plant-derived anti-HIV products have been used in a limited number of patients suffering from AIDS viz. glycyrrhizin, papaverine, trichosanthin, castanospermine, N-butyl-1-deoxynojirimicin and acemannan.

antiviral activity, plant-derived products, anti-HIV properties, anti-AIDS products

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14. (Article ID: 11574)
 
Guan H, Keeling P
Starch biosynthesis: Understanding the functions and interactions of multiple isozymes of starch synthase and branching enzyme
Trends in Glycoscience and Glycotechnology 10(54) (1998) 307-319
 

Starch is the most important source of calories on the planet and a vital storage compound in plants. Despite its importance, we do not fully understand how starch is synthesized, how starch synthesis is initiated and what controls starch structure. Many genes in the starch biosynthesis pathway have been isolated and multiple forms of starch synthase and branching enzyme have been identified. For example, five starch synthase genes and three branching enzyme genes have been cloned from maize. To fully illustrate the mechanism of starch biosynthesis, we need to understand the functions of individual enzyme as well as the concerted actions of multiple forms of enzymes in starch synthesis. Since maize is the number one supply of starch for food and non-food industries and also a good source for genetic and biochemical studies, here we will use maize as a model plant to discuss the mechanism of starch biosynthesis, particularly the initiation of starch synthesis, the functions and interaction of multiple isozymes of starch synthase and branching enzyme.

branching enzyme, starch, maize, starch biosynthesis, starch synthase

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15. (Article ID: 11996)
 
Andary C, Wylde R, Maury L, Heitz A, Dubourg A, Nishibe S
X-ray analysis and extended NMR study of oraposide
Phytochemistry 37(3) (1994) 855-857
 

An X-ray analysis of oraposide, previously reported as orobanchoside and isolated from Orobanche rapum-genistae confirms the originality of an unusual cyclic structure formed by an ether linkage between a glucose molecule and a 3,4-dihydroxyphenylglycol.

Orobanchaceae, X-ray analysis, oraposide, Orobanche rapum-genistae, orobanchoside

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