Laminaritriose

Microarrays are powerful tools for high throughput analysis, and hundreds or thousands of molecular interactions can be assessed simultaneously using very small amounts of analytes. Nucleotide microarrays are well established in plant research, but carbohydrate microarrays are much less established, and one reason for this is a lack of suitable glycans with which to populate arrays. Polysaccharide microarrays are relatively easy to produce because of the ease of immobilizing large polymers noncovalently onto a variety of microarray surfaces, but they lack analytical resolution because polysaccharides often contain multiple distinct carbohydrate substructures. Microarrays of defined oligosaccharides potentially overcome this problem but are harder to produce because oligosaccharides usually require coupling prior to immobilization. We have assembled a library of well characterized plant oligosaccharides produced either by partial hydrolysis from polysaccharides or by de novo chemical synthesis. Once coupled to protein, these neoglycoconjugates are versatile reagents that can be printed as microarrays onto a variety of slide types and membranes. We show that these microarrays are suitable for the high throughput characterization of the recognition capabilities of monoclonal antibodies, carbohydrate-binding modules, and other oligosaccharide-binding proteins of biological significance and also that they have potential for the characterization of carbohydrate-active enzymes.

Many phytopathogens secrete cell wall degradation enzymes (CWDEs) to damage host cells and facilitate colonization. As the major components of the plant cell wall, cellulose and hemicellulose are the targets of CWDEs. Damaged plant cells often release damage-associated molecular patterns (DAMPs) to trigger plant immune responses. Here, we establish that the fungal pathogen Magnaporthe oryzae secretes the endoglucanases MoCel12A and MoCel12B during infection of rice (Oryza sativa). These endoglucanases target hemicellulose of the rice cell wall and release two specific oligosaccharides, namely the trisaccharide 3¹-β-D-Cellobiosyl-glucose and the tetrasaccharide 3¹-β-D-Cellotriosyl-glucose. 3¹-β-D-Cellobiosyl-glucose and 3¹-β-D-Cellotriosyl-glucose bind the immune receptor OsCERK1 but not the chitin binding protein OsCEBiP. However, they induce the dimerization of OsCERK1 and OsCEBiP. In addition, these Poaceae cell wall-specific oligosaccharides trigger a burst of reactive oxygen species (ROS) that is largely compromised in oscerk1 and oscebip mutants. We conclude that 3¹-β-D-Cellobiosyl-glucose and 3¹-β-D-Cellotriosyl-glucose are specific DAMPs released from the hemicellulose of rice cell wall, which are perceived by an OsCERK1 and OsCEBiP immune complex during M. oryzae infection in rice.

Maize is a crop of worldwide importance, but insects and plant pathogens limit sustainable production. The development of maize varieties with improved resistance will be facilitated by identification of relevant resistance alleles through appropriate biological assays. A barwin-like gene (which we call maizewin) located in a QTL for Fusarium resistance annotated such that potential glucanase and chitinase activity could occur in the translated protein, was cloned from an ear rot resistant inbred and transgenically expressed in maize callus. Although limited increases in insect resistance occurred in the transgenic callus material containing the maizewin gene compared to a GUS control gene, resistance to Fusarium pathogens was common and associated with increased glucanase activity. The gene appeared to produce a protein with glucanase and chitosanase activity, consistent with an antifungal role. The allele that produces the functional resistant protein may be relatively uncommon in maize germplasm. Incorporation of a functional maizewin allele into susceptible germplasm should help increase production by contributing to control of both insect pests and plant pathogens.

In this report, we present the strategy for the revelation of synergistic effect and elucidation of active fractions from an immunomodulatory complex polysaccharide derived from seven herbs (Lentinula edodes, Ganodorma lucidum, Tremella fuciformis, Chrysanthemum, Lycium barbarum, Codonopsis pilosula and Poria cocos), a formula used as health product in China market, using the combination of HPSEC-MALLS, immunological bioassay and saccharide mapping analysis. The effects of complex polysaccharide and their fractions on RAW 246.7 macrophages demonstrated that the fractions (CD1, CD2, CD3) with molecular weight above 10 kDa exhibited immune activity by directly stimulated NO release and phagocytosis, and induced macrophages to secrete cytokines. Especially, fraction CD2 with molecular weight of 100-1000 kDa showed the strongest bioactivity (EC₅₀ = 0.19 μg/mL) compared with their individual corresponding herbal polysaccharides fractions due to synergistic effect, which supported the scientific use of Chinese herbal mixture. Moreover, their chemical characters were analyzed by HPSEC-MALLS and saccharide mapping, and the original herbs, including L. edodes, G. lucidum, T. fuciformis and Chrysanthemum, responsible for the immunomodulatory activity were tentatively revealed. Results are beneficial for the quality analysis and formula optimization of complex polysaccharides in both biomedical and functional food field.

A novel β-1,3-1,4-glucanase in the glycoside hydrolase family 5 (GH5) has been identified in the secretome of Paenibacillus polymyxa KF-1. The recombinant GH5 enzyme PpBglu5A shows broad substrate specificity, with strong lichenase activity, medium β-1,3-glucanase activity, and minimal cellulase activity. Barley β-glucan, lichenan, curdlan, and carboxymethyl cellulose are hydrolyzed to varying degrees by PpBglu5A, with the highest catalytic activity being observed with barley β-glucan. Hydrolysates from barley β-glucan or lichenan are primarily glucan oligosaccharides with degrees of polymerization from 2 to 4. PpBglu5A also hydrolyzes oat bran into oligosaccharides mainly consisted of di-, tri-, and tetra- oligosaccharides that are useful in the preparation of gluco-oligosaccharides. In addition to hydrolytic activity, transglycosylation was also observed with PpBglu5A and cellotriose as substrate. An in vitro assay indicated that the recombinant PpBglu5A has antifungal activity and can inhibit the growth of Canidia albicans. These results suggest that PpBglu5A exhibits unique properties and may be useful as an antifungal agent.

We previously reported that β-glucosidase BGL1 at low concentration (15 µg mL^-1) from Coprinopsis cinereal exhibited hydrolytic activity only toward laminarioligosaccharides but not toward cellooligosaccharides and gentiobiose. This study shows that BGL1 at high concentration (200 µg mL^-1) also hydrolyzed cellobiose and gentiobiose, which accounted for only 0.83 and 2.05% of its activity toward laminaribiose, respectively. Interestingly, BGL1 at low concentration (1.5 µg mL^-1) showed transglycosylation but BGL1 at high concentration (200 µg mL^-1) did not. BGL1 utilizes only laminarioligosaccharides but not glucose, gentiobiose, and cellobiose to synthesize the higher oligosaccharides. BGL1 transferred one glucosyl residue from substrate laminarioligosaccharide to another laminarioligosaccharide as an acceptor in a β(1 → 3) or β(1 → 6) fashion to produce higher laminarioligosaccharides or 3-O-β-D-gentiobiosyl-D-laminarioligosaccharides. The BGL1-digested laminaritriose exhibited approximately 90% enhancement in the anti-oxidant activity compared to that of untreated laminaritriose, implying a potential application of BGL1-based transglycosylation for the production of high value-added rare oligosaccharides.

Laminarinases exhibit potential in a wide range of industrial applications including the production of biofuels and pharmaceuticals. In this study, we present the genetic and biochemical characteristics of FLamA and FLamB, two laminarinases derived from a metagenomic sample from a hot spring in the Azores. Sequence comparison revealed that both genes had high similarities to genes from Fervidobacterium nodosum Rt17-B1. The two proteins showed sequence similarities of 62% to each other and belong to the glycoside hydrolase (GH) family 16. For biochemical characterization, both laminarinases were heterologously produced in Escherichia coli and purified to homogeneity. FLamA and FLamB exhibited similar properties and both showed highest activity towards laminarin at 90° C and pH 6.5. The two enzymes were thermostable but differed in their half-life at 80° C with 5 h and 1 h for FLamA and FLamB, respectively. In contrast to other laminarinases, both enzymes prefer β-1,3-glucans and mixed-linked glucans as substrates. However, FLamA and FLamB differ in their catalytic efficiency towards laminarin. Structure predictions were made and showed minor differences particularly in a kink adjacent to the active site cleft. The high specific activities and resistance to elevated temperatures and various additives make both enzymes suitable candidates for application in biomass conversion.

Fungal cell wall synthesis is achieved by a balance of glycosyltransferase, hydrolase and transglycosylase activities. Transglycosylases strengthen the cell wall by forming a rigid network of crosslinks through mechanisms that remain to be explored. Here we study the function of the Aspergillus fumigatus family of five Crh transglycosylases. Although crh genes are dispensable for cell viability, simultaneous deletion of all genes renders cells sensitive to cell wall interfering compounds. In vitro biochemical assays and localisation studies demonstrate that this family of enzymes functions redundantly as transglycosylases for both chitin-glucan and chitin-chitin cell wall crosslinks. To understand the molecular basis of this acceptor promiscuity, we solved the crystal structure of A. fumigatus Crh5 (AfCrh5) in complex with a chitooligosaccharide at the resolution of 2.8 Å, revealing an extensive elongated binding cleft for the donor (−4 to −1) substrate and a short acceptor (+1 to +2) binding site. Together with mutagenesis, the structure suggests a “hydrolysis product assisted” molecular mechanism favouring transglycosylation over hydrolysis.

We previously reported that an endo-β-1,3(4)-d-glucanase, Eng16A, from C. cinerea shows a higher degradation activity toward barley β-glucan than laminarin. HPAEC-PAD and Q-TOF-MS/MS analyses show that Eng16A-digestion products of barley β-glucan not only contain some oligosaccharides with (1 → 3)-β-linkage adjacent to the reducing end, which is consistent with β-1,3(4)-glucanase-digestion products, but also include some oligosaccharides containing (1 → 4)-β-linkage adjacent to the reducing end which is consistent with cellulase-digestion products. Thus, Eng16A possesses both cellulase and β-1,3(4)-glucanase activities. Because Eng16A does not degrade cellulose, we propose that the insertion of a (1 → 3)-β-linkage among the groups of (1 → 4)-β-linkages may make these (1 → 4)-β-linkages prone to cleavage by Eng16A. Furthermore, Eng16A also possesses transglycosylation activity which leads to some products containing one or a few consecutive (1 → 3)-β-linkages adjacent to the non-reducing end. Therefore, HPAEC-PAD and Q-TOF-MS/MS analyses provide an efficient approach to reveal complicated modes of action of some endo-β-1,3(4)-d-glucanases on barley β-glucan.

Marine bacteria catabolize carbohydrate polymers of algae, which synthesize these structurally diverse molecules in ocean surface waters. Although algal glycans are an abundant carbon and energy source in the ocean, the molecular details that enable specific recognition between algal glycans and bacterial degraders remain largely unknown. Here we characterized a surface protein, GMSusD from the planktonic Bacteroidetes‐Gramella sp. MAR_2010_102 that thrives during algal blooms. Our biochemical and structural analyses show that GMSusD binds glucose polysaccharides such as branched laminarin and linear pustulan. The 1.8 Å crystal structure of GMSusD indicates that three tryptophan residues form the putative glycan‐binding site. Mutagenesis studies confirmed that these residues are crucial for laminarin recognition. We queried metagenomes of global surface water datasets for the occurrence of SusD‐like proteins and found sequences with the three structurally conserved residues in different locations in the ocean. The molecular selectivity of GMSusD underscores that specific interactions are required for laminarin recognition. In conclusion, our findings provide insight into the molecular details of β‐glucan binding by GMSusD and our bioinformatic analysis reveals that this molecular interaction may contribute to glucan cycling in the surface ocean.

We report the first hydrothermal hydrolysis of curdlan, a water insoluble β-1,3-glucan, to produce β-1,3-glucooligosaccharides, which are high-value materials with health-benefiting activities. In this study, hydrothermal hydrolysis was tested for the liquefaction and saccharification of curdlan. The optimal hydrothermal hydrolysis conditions were 180°C and 60 min, respectively, resulting in a high degree of liquefaction (98.4%) and low byproduct formation. Under the optimal conditions, 17.47 g/L of β-1,3-glucooligosaccharides was produced from 20 g/L of curdlan, representing a conversion yield of 87.4% (w/w). Using this process, β-1,3-glucooligosaccharides were conveniently produced in a one-step reaction without any chemicals or enzymes. This hydrothermal hydrolysis for curdlan exhibited the best performance among various hydrolysis processes reported to date. This method can be applied to large-scale production of β-1,3-glucooligosaccharides for the functional food and biopharmaceutical industries.

The rising importance of accurately detecting oligosaccharides in biomass hydrolyzates or as ingredients in food, such as in beverages and infant milk products, demands for the availability of tools to sensitively analyze the broad range of available oligosaccharides. Over the last decades, HPAEC-PAD has been developed into one of the major technologies for this task and represents a popular alternative to state-of-the-art LC-MS oligosaccharide analysis. This work presents the first comprehensive study which gives an overview of the separation of 38 analytes as well as enzymatic hydrolyzates of six different polysaccharides focusing on oligosaccharides. The high sensitivity of the PAD comes at cost of its stability due to recession of the gold electrode. By an in-depth analysis of the sensitivity drop over time for 35 analytes, including xylo- (XOS), arabinoxylo- (AXOS), laminari- (LOS), manno- (MOS), glucomanno- (GMOS), and cellooligosaccharides (COS), we developed an analyte-specific one-phase decay model for this effect over time. Using this model resulted in significantly improved data normalization when using an internal standard. Our results thereby allow a quantification approach which takes the inevitable and analyte-specific PAD response drop into account.

The chain conformation, chemical characters and immunomodulatory activity of polysaccharide from Dendrobium devonianum (DDP) were investigated.Results showed that molecular weights, polydispersity index, radius of gyrations of DDP were 3.99 × 10⁵ Da, 1.27, 74.1 nm, respectively. By applying the polymer solution theory, the exponent (v) values of <S²>_z ^1/2 = kM_w^v was calculated as 0.38, which revealed that DDP existed as a globular shape in aqueous solution, and further confirmed by AFM analysis. Furthermore, the main monosaccharide compositions were Man and Glc with the ratio of 29.61:1.00. Indeed, the main glycosidic linkages were β-1,4-Manp, and substituted with acetyl groups at O-2 and O-3 position. Notably, DDP could promote the immune functions of macrophages including NO release and phagocytosis. Thus, DDP could be explored as a natural immune-stimulating agent in the health and functional food area as well as pharmaceutical industries.

Water-soluble polysaccharides from 51 batches of fruits of L. barbarum (wolfberry) in China were investigated and compared using saccharide mapping, partial acid hydrolysis, single and composite enzymatic digestion, followed by polysaccharide analysis by using carbohydrate gel electrophoresis (PACE) analysis and high performance thin layer chromatography (HPTLC) analysis, respectively. Results showed that multiple PACE and HPTLC fingerprints of partial acid and enzymatic hydrolysates of polysaccharides from L. barbarum in China were similar, respectively. In addition, results indicated that β-1,3-glucosidic, α-1,4-galactosiduronic and α-1,5-arabinosidic linkages existed in polysaccharides from L. barbarum collected in China, and the similarity of polysaccharides in L. barbarum collected from different regions of China was pretty high, which are helpful for the improvement of the performance of polysaccharides from L. barbarum in functional/health foods area. Furthermore, polysaccharides from Panax notoginseng, Angelica sinensis, and Astragalus membranaceus var. mongholicus were successfully distinguished from those of L. barbarum based on their PACE fingerprints. These results were beneficial to improve the quality control of polysaccharides from L. barabrum and their products, which suggested that saccharide mapping based on PACE and HPTLC analysis could be a routine approach for quality control of polysaccharides.

A laminarinase (endo-β-1,3-glucanase) was purified to homogeneity from Penicillium rolfsii c3-2(1) IBRL, which was originally produced in liquid culture containing 1% xylan from birchwood, via anion-exchange chromatography, gel filtration on Sephacryl S-100, and hydrophobic interaction chromatography. A single protein band with a molecular weight of 75 kDa was detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, which had an optimum catalytic activity at pH 4.0 to 5.0 and 70°C. This purified enzyme was most stable in the pH range 4 to 7, while it was thermostable up to 55°C and retained up to 90% of its activity after 4 h pre-incubation. A substrate laminarin kinetic study yielded estimated K_m and V_max values of 0.0817 mg/mL and 372.2 µmol/min/mg, respectively. Laminari-oligosaccharide degradation, which was analyzed by thin layer chromatography, yielded the major hydrolysis products laminaribiose and glucose.

Using chromatographic technique, xyloglucanase (XG) A (25 kDa, pI 3.5, 12th glycosyl hydrolase family) was isolated from the enzyme complex secreted by the mycelial fungus Penicillium canescens, and xyloglucanases XG 25 (25 kDa, pI 4.1, 12th glycosyl hydrolase family) and XG 70 (70 kDa, pI 3.5, 74th glycosyl hydrolase family) were isolated from the enzyme complex of Penicillium verruculosum. Properties of the isolated enzymes (substrate specificity, optimal ranges of pH and temperature for enzyme activity and stability, effect of metal ions on catalytic activity) were compared with the properties of xyloglucanases XG 32 of Aspergillus japonicus, XG 78 of Chrysosporium lucknowense, and XG of Trichoderma reesei. The gene xegA encoding XG A of P. canescens was isolated, and the amino acid sequence of the corresponding protein was determined.

Using chromatography on different matrixes, three β-glucosidases (120, 116, and 70 kDa) were isolated from enzymatic complexes of the mycelial fungi Aspergillus japonicus, Penicillium verruculosum, and Trichoderma reesei, respectively. The enzymes were identified by MALDI-TOF mass-spectrometry. Substrate specificity, kinetic parameters for hydrolysis of specific substrates, ability to catalyze the transglucosidation reaction, dependence of the enzymatic activity on pH and temperature, stability of the enzymes at different temperatures, adsorption ability on insoluble cellulose, and the influence of glucose on catalytic properties of the enzymes were investigated. According to the substrate specificity, the enzymes were shown to belong to two groups: i) β-glucosidase of A. japonicus exhibiting high specific activity to the low molecular weight substrates cellobiose and pNPG (the specific activity towards cellobiose was higher than towards pNPG) and low activity towards polysaccharide substrates (β-glucan from barley and laminarin); ii) β-glucosidases from P. verruculosum and T. reesei exhibiting relatively high activity to polysaccharide substrates and lower activity to low molecular weight substrates (activity to cellobiose was lower than to pNPG).

A gene cluster involved in maltodextrin transport and metabolism was identified in the genome of Lactobacillus acidophilus NCFM, which encoded a maltodextrin-binding protein, three maltodextrin ATP-binding cassette transporters and five glycosidases, all under the control of a transcriptional regulator of the LacI-GalR family. Enzymatic properties are described for recombinant maltose phosphorylase (MalP) of glycoside hydrolase family 65 (GH65), which is encoded by malP (GenBank: AAV43670.1) of this gene cluster and produced in Escherichia coli. MalP catalyses phosphorolysis of maltose with inversion of the anomeric configuration releasing β-glucose 1-phosphate (β-Glc 1-P) and glucose. The broad specificity of the aglycone binding site was demonstrated by products formed in reverse phosphorolysis using various carbohydrate acceptor substrates and β-Glc 1-P as the donor. MalP showed strong preference for monosaccharide acceptors with equatorial 3-OH and 4-OH, such as glucose and mannose, and also reacted with 2-deoxy glucosamine and 2-deoxy N-acetyl glucosamine. By contrast, none of the tested di- and trisaccharides served as acceptors. Disaccharide yields obtained from 50 mM β-Glc 1-P and 50 mM glucose, glucosamine, N-acetyl glucosamine, mannose, xylose or L-fucose were 99, 80, 53, 93, 81 and 13%, respectively. Product structures were determined by NMR and ESI-MS to be α-Glcp-(1→4)-Glcp (maltose), α-Glcp-(1→4)-GlcNp (maltosamine), α-Glcp-(1→4)-GlcNAcp (N-acetyl maltosamine), α-Glcp-(1→4)-Manp, α-Glcp-(1→4)-Xylp and α-Glcp-(1→4)-L-Fucp, the three latter being novel compounds. Modelling using L. brevis GH65 as the template and superimposition of acarbose from a complex with Thermoanaerobacterium thermosaccharolyticum GH15 glucoamylase suggested that loop 3 of MalP involved in substrate recognition blocked the binding of candidate acceptors larger than monosaccharides.

The murine molecule dectin-1 (known as the β-glucan receptor in humans) is an immune cell surface receptor implicated in the immunological defense against fungal pathogens. Sequence analysis has indicated that the dectin-1 extracellular domain is a C-type lectin-like domain, and functional studies have established that it binds fungal β-glucans. We report several dectin-1 crystal structures, including a high-resolution structure and a 2.8 Å resolution structure in which a short soaked natural β-glucan is trapped in the crystal lattice. In vitro characterization of dectin-1 in the presence of its natural ligand indicates higher-order complex formation between dectin-1 and β-glucans. These combined structural and biophysical data considerably extend the current knowledge of dectin-1 structure and function, and suggest potential mechanisms of defense against fungal pathogens.