Rhamnogalacturonan I Backbone Research Articles

Structural elucidation of novel pro-inflammatory polysaccharides from Daphne mezereum L.

Daphne mezereum L., an important medicinal plant in Scandinavian folk medicine, was used to treat ailments such as diarrhea, swelling and stomach pain. A range of natural compounds have been isolated, but little attention has been given to the polysaccharides in this plant. Previous work in our group have shown that a polysaccharide enriched fraction from the bark of D. mezereum exhibited pro-inflammatory effects. To pursue this further, the aim of the present work was to isolate and characterize these polysaccharides. From the ethanol-precipitate of a water extract, one neutral (DMP-NF) and one acidic (DMP-AF) fraction was isolated by anion-exchange chromatography. GC, GC–MS and 1D- and 2D-NMR were used to characterize the polysaccharide structures. DMP-NF appeared to be a mixture of arabinan, arabinogalactan and hemicelluloses such as xyloglucan, mannan and xylan. DMP-AF contained a pectic polysaccharide mainly consisting of an unusually long homogalacturonan backbone. Enzymatic treatment by pectinase of DMP-AF yielded DMP-ED, which contained a rhamnogalacturonan-I backbone with arabinan, galactan and arabinogalactan side chains. Both DMP-NF and DMP-ED induced IFN-γ and TNF-α secretion in peripheral blood mononuclear cells (PBMCs), DMP-ED being the most potent fraction. DMP-AF was less active, which might be due to a less sterically available rhamnogalacturonan-I domain.

A ginseng-derived rhamnogalacturonan I (RG-I) pectin promotes longevity via TOR signalling in Caenorhabditis elegans

Panax ginseng C. A. Meyer (ginseng), a traditional Chinese herb, is usually used to improve health and increase anti-aging activity for human. Polysaccharides are bioactive components of ginseng. Herein, using Caenorhabditis elegans as a model, we discovered a ginseng-derived rhamnogalacturonan I (RG-I) pectin WGPA-1-RG promoted longevity via TOR signalling pathway with transcription factors FOXO/DAF-16 and Nrf2/SKN-1 accumulated in the nucleus, where they activated target genes. And the WGPA-1-RG-mediated lifespan extension was dependent on endocytosis, rather than a bacterial metabolic process. Glycosidic linkage analyses combined with arabinose- and galactose-releasing enzyme hydrolyses identified the RG-I backbone of WGPA-1-RG was primarily substituted with α-1,5-linked arabinan, β-1,4-linked galactan and arabinogalactan II (AG-II) side chains. Feeding worms with the WGPA-1-RG-derived fractions which lost distinct structural elements by enzymatic digestions, we found the arabinan side chains prominently contributed to the longevity-promoting activity of WGPA-1-RG. These findings provide a novel ginseng-derived nutrient that potentially increases human longevity.

Polymerization of the backbone of the pectic polysaccharide rhamnogalacturonan I.

Rhamnogalacturonan I (RG-I) is a major plant cell wall pectic polysaccharide defined by its repeating disaccharide backbone structure of [4)-α-D-GalA-(1,2)-α-L-Rha-(1,]. A family of RG-I:Rhamnosyltransferases (RRT) has previously been identified, but synthesis of the RG-I backbone has not been demonstrated in vitro because the identity of Rhamnogalacturonan I:Galaturonosyltransferase (RG-I:GalAT) was unknown. Here a putative glycosyltransferase, At1g28240/MUCI70, is shown to be an RG-I:GalAT. The name RGGAT1 is proposed to reflect the catalytic activity of this enzyme. When incubated together with the rhamnosyltransferase RRT4, the combined activities of RGGAT1 and RRT4 result in elongation of RG-I acceptors in vitro into a polymeric product. RGGAT1 is a member of a new GT family categorized as GT116, which does not group into existing GT-A clades and is phylogenetically distinct from the GALACTURONOSYLTRANSFERASE (GAUT) family of GalA transferases that synthesize the backbone of the pectin homogalacturonan. RGGAT1 has a predicted GT-A fold structure but employs a metal-independent catalytic mechanism that is rare among glycosyltransferases with this fold type. The identification of RGGAT1 and the 8-member Arabidopsis GT116 family provides a new avenue for studying the mechanism of RG-I synthesis and the function of RG-I in plants.

Pectin from leaves of birch (Betula pendula Roth.): Results of NMR experiments and hypothesis of the RG-I structure

We report that in birch leaf pectin, rhamnogalacturonan-I (RG-I) and galacturonan (HG) were found as separate polymers rather than domains of a complex macromolecule. RG-I and HG were separated by anion-exchange and size-exclusion chromatography and studied by using NMR spectroscopy. NMR spectra showed that methyl-esterified D-galactosyluronic acid residues were located only in HG. Oligosaccharides of similar structure to the backbone, but without terminal reducing residues in the NMR spectra, were found in RG-I. We hypothesize, these oligosaccharides and RG-I backbone can be covalently bound due to its co-eluted of from DEAE-cellulose and Sepharose CL-4B. This result differs from the classical RG-I model, which assumes that all Rhap and GalpA residues are located only in the RG-I backbone. In the heteronuclear multiple bond correlation (HMBC) and rotating frame Overhauser effect spectroscopy (ROESY) spectra, the correlation peaks confirming the substitution of 2,4-rhamnose residues at O-4 by only single D-galactose residues were identified.

Pectin Modification in Seed Coat Mucilage by In Vivo Expression of Rhamnogalacturonan-I- and Homogalacturonan-Degrading Enzymes.

The cell wall is essential for plant survival. Determining the relationship between cell wall structure and function using mutant analysis or overexpressing cell wall-modifying enzymes has been challenging due to the complexity of the cell wall and the appearance of secondary, compensatory effects when individual polymers are modified. In addition, viability of the plants can be severely impacted by wall modification. A useful model system for studying structure-function relationships among extracellular matrix components is the seed coat epidermal cells of Arabidopsis thaliana. These cells synthesize relatively simple, easily accessible, pectin-rich mucilage that is not essential for plant viability. In this study, we expressed enzymes predicted to modify polysaccharide components of mucilage in the apoplast of seed coat epidermal cells and explored their impacts on mucilage. The seed coat epidermal-specific promoter TESTA ABUNDANT2 (TBA2) was used to drive expression of these enzymes to avoid adverse effects in other parts of the plant. Mature transgenic seeds expressing Rhamnogalacturonate lyase A (RglA) or Rhamnogalacturonate lyase B (RglB) that degrade the pectin rhamnogalacturonan-I (RG-I), a major component of mucilage, had greatly reduced mucilage capsules surrounding the seeds and concomitant decreases in the monosaccharides that comprise the RG-I backbone. Degradation of the minor mucilage component homogalacturonan (HG) using the HG-degrading enzymes Pectin lyase A (PLA) or ARABIDOPSIS DEHISCENCE ZONE POLYGALACTURONASE2 (ADPG2) resulted in developing seed coat epidermal cells with disrupted cell-cell adhesion and signs of early cell death. These results demonstrate the feasibility of manipulating the seed coat epidermal cell extracellular matrix using a targeted genetic engineering approach.

Root-knot nematode chemotaxis is positively regulated by l-galactose sidechains of mucilage carbohydrate rhamnogalacturonan-I.

Root-knot nematodes (RKNs) are plant parasites and major agricultural pests. RKNs are thought to locate hosts through chemotaxis by sensing host-secreted chemoattractants; however, the structures and properties of these attractants are not well understood. Here, we describe a previously unknown RKN attractant from flaxseed mucilage that enhances infection of Arabidopsis and tomato, which resembles the pectic polysaccharide rhamnogalacturonan-I (RG-I). Fucose and galactose sidechains of the purified attractant were found to be required for attractant activity. Furthermore, the disaccharide α-l-galactosyl-1,3-l-rhamnose, which forms the linkage between the RG-I backbone and galactose sidechains of the purified attractant, was sufficient to attract RKN. These results show that the α-l-galactosyl-1,3-l-rhamnose linkage in the purified attractant from flaxseed mucilage is essential for RKN attraction. The present work also suggests that nematodes can detect environmental chemicals with high specificity, such as the presence of chiral centers and hydroxyl groups.

Isolation and structure characterization of a low methyl-esterified pectin from the tuber of Dioscorea opposita Thunb.

A low methyl-esterified pectin (33.2% methyl-esterification degree) was isolated from the tuber of Dioscorea opposita Thunb., which was an edible and medicinal material in China. This pectin (Mw of 1.3 × 104 g/mol) contained the ~59.1% homogalacturonan (HG) and ~38.1% highly branched rhamnogalacturonan I (RG-I) region with possible side chains embracing arabinogalactan II, arabinan or arabinogalactan I. The fragments including HG backbone consisting of → 4)-α-GalpA-(1 → and → 4)-α-GalpA-6-O-methyl-(1 → with molar ratio of ~2:1, and repeating unit of arabinogalactan II side chain composed of α-Araf-(1 → and → 3,6)-β-Galp-(1→, were speculated through methylation analysis and NMR spectra. However, the linkage pattern for RG-I backbone and side chains were indiscernible due to limited resolution of NMR spectra. Besides, the pectin adopted a flexible chain conformation in 0.1 M NaNO3 solution. These results provided a structural basis for study on polysaccharide from D. opposite, which was benefit for development of functional food of yam.

Structural characteristics of a highly branched and acetylated pectin from Portulaca oleracea L.

The water-extracted polysaccharide from Portulaca oleracea L. mainly consisted of two pectic polysaccharides designated as POWP-H and POWP-L. The POWP-L was rich in linear homogalacturonan with GalA content of 77.6%, while POWP-H might be a rhamnogalacturonan I (RG-I) pectin composed of Rha (15.7%), Ara (31.7%), Gal (42.5%) and GalA (10.1%). The structure of POWP-H was elucidated by partial degradation, methylation analysis combined with GC-MS method and NMR spectroscopy. It had a weight-average molecular weight of 1.2 × 106 g/mol and high degree of branch of 0.57. The presence of abundant arabinogalactan-II and certain galactan side chains in POWP-H was verified by the T-Araf (17.4%), 1,3,6-Galp (11.8%), 1,3-Galp (8.1%), T-Galp (13.4%) and 1,4-Galp (14.3%). The evidence for the RG-I backbone of POWP-H was demonstrated by the structure analysis of its degraded product POWP-H-H, which had the backbone of →4)-α-GalpA-(1 → 2)-α-Rhap-(1 → 4)-α-GalpA-(1 → 2,4)-α-Rhap-(1→ substituted by short side chain of β-Galp-(1 → 4)-β-Galp-(1→ at O-4 position of →2,4)-α-Rhap-(1 → . Moreover, the POWP-H-H was mainly O-acetylated at O-3 position of α-Rhap with 24.8% acetylation degree. In conclusion, POWP-H was mainly the highly branched and acetylated RG-I pectin with relative short RG-I backbone and abundant arabinogalactan II and certain galactan side chains. Besides, it adopted a flexible chain conformation in 0.1 M NaNO3 solution.

Diversity of Pectin Rhamnogalacturonan I Rhamnosyltransferases in Glycosyltransferase Family 106.

Rhamnogalacturonan I (RG-I) comprises approximately one quarter of the pectin molecules in land plants, and the backbone of RG-I consists of a repeating sequence of [2)-α-L-Rha(1-4)-α-D-GalUA(1-] disaccharide. Four Arabidopsis thaliana genes encoding RG-I rhamnosyltransferases (AtRRT1 to AtRRT4), which synthesize the disaccharide repeats, have been identified in the glycosyltransferase family (GT106). However, the functional role of RG-I in plant cell walls and the evolutional history of RRTs remains to be clarified. Here, we characterized the sole ortholog of AtRRT1–AtRRT4 in liverwort, Marchantia polymorpha, namely, MpRRT1. MpRRT1 had RRT activity and genetically complemented the AtRRT1-deficient mutant phenotype in A. thaliana. However, the MpRRT1-deficient M. polymorpha mutants showed no prominent morphological changes and only an approximate 20% reduction in rhamnose content in the cell wall fraction compared to that in wild-type plants, suggesting the existence of other RRT gene(s) in the M. polymorpha genome. As expected, we detected RRT activities in other GT106 family proteins such as those encoded by MpRRT3 in M. polymorpha and FRB1/AtRRT8 in A. thaliana, the deficient mutant of which affects cell adhesion. Our results show that RRT genes are more redundant and diverse in GT106 than previously thought.

Rhamnogalacturonan I galactosyltransferase: Detection of enzyme activity and its hyperactivation

Rhamnogalacturonan I (RG-I), one of the pectic components of the plant cell wall, is composed of a backbone of repeating disaccharide units of rhamnose and galacturonic acid, and side chains, such as galactans, arabinans, and arabinogalactans. The activity of RG-I galactosyltransferase, which transfers galactosyl residues to rhamnosyl residues in the RG-I backbone, has not been detected until now. Here, we detected galactosyltransferase activity in azuki bean epicotyls using fluorogenic RG-I oligosaccharide acceptors. This enzyme prefers oligosaccharides with a degree of polymerization more than 9. The enzyme activity was detected in the Golgi apparatus, which is the site of pectin synthesis. In vitro hyperactivation of this enzyme was also observed. Moreover, enzyme activity was increased up to 40-fold in the presence of cationic surfactants or polyelectrolytes.

Rhamnogalacturonan lyase: a pectin modification enzyme of higher plants

Plant cell wall is constituted by three main polysaccharides: cellulose, hemicellulose and pectin. The principal pectin domains comprise homogalacturonan, rhamnogalacturonan I (RG-I) and ramnogalacturonan II. Rhamnogalacturonan lyase (RGL) enzyme is capable of catalyzing the degradation of the RG-I backbone by a b-elimination mechanism. RGL enzyme have been studied in fungi and bacteria species, however, little data is available related with its function in plant biology. This review tries to fill the gaps on the knowledge about RGL enzyme. Here, we discuss our recent published work regarding the role of RGL in plants. In addition, we highlight results from different sequence analysis, RGL activity and function associated with plant development and fruit ripening, as well as its role in cell wall structure. The knowledge of this enzyme is essential to comprehend and elucidate its role in plant and fruit physiology.

The Three Members of the Arabidopsis Glycosyltransferase Family 92 are Functional β-1,4-Galactan Synthases.

Pectin is a major component of primary cell walls and performs a plethora of functions crucial for plant growth, development and plant-defense responses. Despite the importance of pectic polysaccharides their biosynthesis is poorly understood. Several genes have been implicated in pectin biosynthesis by mutant analysis, but biochemical activity has been shown for very few. We used reverse genetics and biochemical analysis to study members of Glycosyltransferase Family 92 (GT92) in Arabidopsis thaliana. Biochemical analysis gave detailed insight into the properties of GALS1 (Galactan synthase 1) and showed galactan synthase activity of GALS2 and GALS3. All proteins are responsible for adding galactose onto existing galactose residues attached to the rhamnogalacturonan-I (RG-I) backbone. Significant GALS activity was observed with galactopentaose as acceptor but longer acceptors are favored. Overexpression of the GALS proteins in Arabidopsis resulted in accumulation of unbranched β-1, 4-galactan. Plants in which all three genes were inactivated had no detectable β-1, 4-galactan, and surprisingly these plants exhibited no obvious developmental phenotypes under standard growth conditions. RG-I in the triple mutants retained branching indicating that the initial Gal substitutions on the RG-I backbone are added by enzymes different from GALS.

Pectin RG-I rhamnosyltransferases represent a novel plant-specific glycosyltransferase family.

Pectin is one of the three key cell wall polysaccharides in land plants and consists of three major structural domains: homogalacturonan, rhamnogalacturonan I (RG-I) and RG-II. Although the glycosyltransferase required for the synthesis of the homogalacturonan and RG-II backbone was identified a decade ago, those for the synthesis of the RG-I backbone, which consists of the repeating disaccharide unit [→2)-α-L-Rha-(1 → 4)-α-D-GalUA-(1→], have remained unknown. Here, we report the identification and characterization of Arabidopsis RG-I:rhamnosyltransferases (RRTs), which transfer the rhamnose residue from UDP-β-L-rhamnose to RG-I oligosaccharides. RRT1, which is one of the four Arabidopsis RRTs, is a single-spanning transmembrane protein, localized to the Golgi apparatus. RRT1 was highly expressed during formation of the seed coat mucilage, which is a specialized cell wall with abundant RG-I. Loss-of-function mutation in RRT1 caused a reduction in the level of RG-I in the seed coat mucilage. The RRTs belong to a novel glycosyltransferase family, now designated GT106. This is a large plant-specific family, and glycosyltransferases in this family seem to have plant-specific roles, such as biosynthesis of plant cell wall polysaccharides.

Gelation of rhamnogalacturonan I is based on galactan side chain interaction and does not involve chemical modifications

The article presents the structural principles of microwave-induced formation of new gel type from pectic rhamnogalacturonan I (RG-I). The backbone of gel-forming RG-I does not contain consecutive galacturonic residues and modifying groups that can be the cause of junction zone formation as it occurs in course of classical ways of pectin gelation. Microwave irradiation does not cause destruction and chemical modifications of RG-I. Removal of half of galactan chains from RG-I leads to loss of gelling capability pointing out on their leading role in this process. Rising of intensity of the bands attributed to galactose and glycosidic linkages in RG-I gel comparing to solution where this polymer exists as molecule associate indicates that the spatial organization of galactans in gel is changed. A model of the RG-I gelation is proposed: being destabilized at volumetric microwave heating RG-I associates are repacked forming network where RG-I molecules are entangled by galactan chains.

Fractionation and structural characterization of six purified rhamnogalacturonans type I from flaxseed mucilage

An improved method for the qualitative fractionation of water-soluble mucilage (WSM) polysaccharides isolated from flaxseed (Linum usitatissimum) comprising ion-exchange chromatography coupled with an evaporative light scattering detector was developed. One neutral fraction (NWSM) and six acidic fractions (AWSM-1 to AWSM-6) were purified. The molecular weights of NWSM, AWSM-1 - AWSM-6, determined using SEC/MALLS, were 1300 kDa, 756.4 kDa, 718.8 kDa, 505.6 kDa, 457.5 kDa, 354.8 kDa and 593.2 kDa, respectively. Monosaccharide composition and linkage analysis confirmed that NWSM was an arabinoxylan with a (1 → 4)-xylan backbone to which terminal arabinose residues and putative short-chain monosaccharides were attached at positions 2 and/or 3. On the other hand, it was shown that the six acidic fractions had similar rhamnogalacturonan I (RG-I) blocks that can be monosubstituted at O-3 position of rhamnose, mostly by terminal galactose or terminal fucose and occasionally by short side-chains of neutral monosaccharides. The calculated rhamnose/galacturonic acid ratio was from 1.22 to 0.85, which remained virtually unchanged and close to 1. The degree of branching of the isolated RG-I fractions was estimated at 0.33 to 0.65. The structural variability of the acidic fractions appeared not to be related to the RG-I backbone but possibly to the type and degree of substitution. These results might serve as a basis for developing chromatography conditions to contribute towards a better separation of mucilage polysaccharides.

A DUF-246 family glycosyltransferase-like gene affects male fertility and the biosynthesis of pectic arabinogalactans

BackgroundPectins are a group of structurally complex plant cell wall polysaccharides whose biosynthesis and function remain poorly understood. The pectic polysaccharide rhamnogalacturonan-I (RG-I) has two types of arabinogalactan side chains, type-I and type-II arabinogalactans. To date few enzymes involved in the biosynthesis of pectin have been described. Here we report the identification of a highly conserved putative glycosyltransferase encoding gene, Pectic ArabinoGalactan synthesis-Related (PAGR), affecting the biosynthesis of RG-I arabinogalactans and critical for pollen tube growth.ResultsT-DNA insertions in PAGR were identified in Arabidopsis thaliana and were found to segregate at a 1:1 ratio of heterozygotes to wild type. We were unable to isolate homozygous pagr mutants as pagr mutant alleles were not transmitted via pollen. In vitro pollen germination assays revealed reduced rates of pollen tube formation in pollen from pagr heterozygotes. To characterize a loss-of-function phenotype for PAGR, the Nicotiana benthamiana orthologs, NbPAGR-A and B, were transiently silenced using Virus Induced Gene Silencing. NbPAGR-silenced plants exhibited reduced internode and petiole expansion. Cell wall materials from NbPAGR-silenced plants had reduced galactose content compared to the control. Immunological and linkage analyses support that RG-I has reduced type-I arabinogalactan content and reduced branching of the RG-I backbone in NbPAGR-silenced plants. Arabidopsis lines overexpressing PAGR exhibit pleiotropic developmental phenotypes and the loss of apical dominance as well as an increase in RG-I type-II arabinogalactan content.ConclusionsTogether, results support a function for PAGR in the biosynthesis of RG-I arabinogalactans and illustrate the essential roles of these polysaccharides in vegetative and reproductive plant growth.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0780-x) contains supplementary material, which is available to authorized users.

Rhamnogalacturonan lyase reveals a unique three-domain modular structure for polysaccharide lyase family 4

Rhamnogalacturonan lyase (RG-lyase) specifically recognizes and cleaves α-1,4 glycosidic bonds between l-rhamnose and d-galacturonic acids in the backbone of rhamnogalacturonan-I, a major component of the plant cell wall polysaccharide, pectin. The three-dimensional structure of RG-lyase from Aspergillus aculeatus has been determined to 1.5 Å resolution representing the first known structure from polysaccharide lyase family 4 and of an enzyme with this catalytic specificity. The 508-amino acid polypeptide displays a unique arrangement of three distinct modular domains. Each domain shows structural homology to non-catalytic domains from other carbohydrate active enzymes.

Identification of elongating �-1,4-galactosyltransferase activity in mung bean ( Vigna radiata ) hypocotyls using 2-aminobenzaminated 1,4-linked �-d-galactooligosaccharides as acceptor substrates

Galactosyltransferase (GalT) activity that results in the transfer of galactose (Gal) from UDP-Gal to exogenous (1-->4)-beta-galactooligosaccharides labeled with 2-aminobenzamide (2AB) at their reducing ends was identified in a particulate preparation obtained from 2-day-old mung bean (Vigna radiata L. Wilezek) hypocotyls. The enzymes responsible were shown, by high-performance anion-exchange chromatography and normal-phase liquid chromatography-electrospray ionization mass spectrometry, to transfer up to eight Gals to the non-reducing end of 2AB-labeled galactooligosaccharide. Using 1H nuclear magnetic resonance spectroscopy, and beta-galactosidase and endo-beta-(1-->4)-galactanase treatments of the enzymatically formed 2AB-labeled galactooligosaccharides, the newly incorporated Gal residues were shown to be beta-(1-->4) linked. Time-course studies indicated that at least two different types of GalT isoform are involved in the elongation of the acceptor substrates. 2AB-labeled galactoheptaose was the most effective acceptor substrate analyzed, although galactooligosaccharides with a degree of polymerization between 4 and 6 were also acceptor substrates. 2AB-labeled penta- and heptasaccharides (RG5 and RG7) generated from rhamnogalacturonan I (RG-I) were not acceptor substrates, suggesting that the GalTs were not capable of adding Gal residues directly to the RG-I backbone. Maximum GalT activity was obtained at pH 6.5 and 20 degrees C in the presence of 25 mM Mn2+ and 0.75% (w/v) Triton X-100. The enzyme had an apparent Km of 20 microM for 2AB-labeled galactoheptaose and 32 microM for UDP-Gal. The characteristics of the enzyme in mung bean microsomal membranes and the usefulness of fluorogenic 2AB-labeled galactooligosaccharides for the assay of GalT are discussed.

A rhamnogalacturonan lyase in the Clostridium cellulolyticum cellulosome.

Clostridium cellulolyticum secretes large multienzymatic complexes with plant cell wall-degrading activities named cellulosomes. Most of the genes encoding cellulosomal components are located in a large gene cluster: cipC-cel48F-cel8C-cel9G-cel9E-orfX-cel9H-cel9J-man5K-cel9M. Downstream of the cel9M gene, a new open reading frame was discovered and named rgl11Y. Amino acid sequence analysis indicates that this gene encodes a multidomain pectinase, Rgl11Y, containing an N-terminal signal sequence, a catalytic domain belonging to family 11 of the polysaccharide lyases, and a C-terminal dockerin domain. The present report describes the biochemical characterization of a recombinant form of Rgl11Y. Rgl11Y cleaves the alpha-L-Rhap-(1-->4)-alpha-D-GalpA glycosidic bond in the backbone of rhamnogalacturonan I (RGI) via a beta-elimination mechanism. Its specific activity on potato pectic galactan and rhamnogalacturonan was found to be 28 and 3.6 IU/mg, respectively, indicating that Rgl11Y requires galactan decoration of the RGI backbone. The optimal pH of Rgl11Y is 8.5 and calcium is required for its activity. Rgl11Y was shown to be incorporated in the C. cellulolyticum cellulosome through a typical cohesin-dockerin interaction. Rgl11Y from C. cellulolyticum is the first cellulosomal rhamnogalacturonase characterized.

Rhamnogalacturonan I from xylem differentiating zones of Cryptomeria japonica

Rhamnogalacturonan I (RG-I) was isolated from the pectin of the cell wall of xylem differentiating zones of sugi ( Cryptomeria japonica D. Don, gymnosperm) by digesting with endo-α-1,4-polygalacturonase followed by gel-permeation chromatography. Structure of RG-1 was characterized by glycosyl composition and glycosyl linkage analyses, partial acid hydrolysis, and lithium (Li)-treatment in ethylenediamine. The oligosaccharides produced by partial acid hydrolysis showed the backbone of RG-I to be a disaccharide repeating unit of → 4)-α- d-Gal p A-(1 → 2)-α- l-Rha p- (1 → . Arabinan and oligogalactosyl side chains were attached at O-4 of rhamnosyl residues of the backbone. Glycosyl composition and glycosyl linkage analyses suggested that the structures and/or the distribution of the arabinan sidechains of sugi RG-I were different from those of sycamore (angiosperm) RG-I. The backbone of sugi ( Cryptomeria japonica D. Don, gymnosperm) rhamnogalacturonan I (RG-I) comprises a disaccharide repeating unit → 4)-α- d-Gal p A-(1 → 2)-α- l-Rha p-(1 → . Arabinan and oligogalactosyl sidechainds are attached at O-4 of rhamnosyl residues of the backbones.