Types Of Glycosidic Bonds Research Articles

Structural characterization, antioxidant activities and physicochemical properties analysis of a galactose-rich exopolysaccharide produced by Limosilactobacillus fermentum YL-11

Lactobacilli-derived exopolysaccharides (EPSs) are widely regarded as safe and have been employed as potential natural, non-toxic additives and functional agents in food industry. The structural properties of a galactose-rich exopolysaccharide produced by Limosilactobacillus fermentum YL-11 (YL-11 EPS) were investigated with chemical and instrumental analysis. The YL-11 EPS was determined to have a molecular weight (Mw) of 13.2 kDa. Nine different types of glycosidic bonds were identified in YL-11 EPS. The inferred structure of the YL-11 EPS contained the backbone of →2)-β-D-Galp-(1→[3)-β-D-Galp-(1]4 → 3)-β-D-Galp-(1 → 3)-β-D-Galp-(1→, with two side chains, β-D-Galp-(1 → 6)-α-D-Manp-(1 → 6)-[α-D-Glcp-1→2]-α-D-Manp-(1 → 3)-[α-D-Glcp-1→6]-α-D-Glcp-(1 → 3)-[α-D-Glcp-1→6]-α-D-Glcp-(1→ with an acetyl group at the O-3 position of →2,6-α-D-Manp-1→ and α-L-Araf-(1→, which were present at the C6 location of the 1,3-β-D-Galp. The YL-11 EPS showed concentration-dependent antioxidant activities and the DPPH, ABTS, hydroxyl groups and superoxide radicals scavenging rates of 10 mg/mL YL-11 EPS reached 61%, 74%, 35.4% and 40%, respectively. The YL-11 EPS also has a beneficial protective impact on H2O2-injured cells, which pretreatment with YL-11 EPS can substantially decrease ROS levels and enhance SOD enzyme activity. Additionally, the YL-11 EPS exhibited good thickening properties and thermal stability. The EPS's structural information and physicochemical properties provide a basis for studying their structure-function relationships.

Discovery of a class of glycosaminoglycan lyases with ultrabroad substrate spectrum and their substrate structure preferences

Glycosaminoglycan (GAG) lyases are often strictly substrate specific, and it is especially difficult to simultaneously degrade GAGs with different types of glycosidic bonds. Herein, we found a new class of GAG lyases (GAGases) from different bacteria. These GAGases belong to polysaccharide lyase 35 family and share quite low homology with the identified GAG lyases. The most surprising thing is that GAGases can not only degrade three types of GAGs: HA, CS and HS, but even one of them can also degrade alginate. Further investigation of structural preferences revealed that GAGases selectively act on GAG domains composed of non/6-O-/N-sulfated hexosamines and d-glucoronic acids, as well as on alginate domains composed of d-mannuronic acids. Additionally, GAG lyases were once speculated to have evolved from alginate lyases, but no transitional enzymes have been found. The discovery of GAGases not only broadens the category of GAG lyases, provides new enzymatic tools for the structural and functional studies of GAGs with specific structures, but also provides candidates for the evolution of GAG lyases.

Effects of Lactobacillus plantarum FM 17 fermentation on jackfruit polysaccharides: Physicochemical, structural, and bioactive properties

Fermentation is a novel technology for modifying polysaccharides in fruits and improving their bioactivities. In this work, we introduced Lactobacillus plantarum FM 17 to ferment jackfruit pulp and subsequently purified polysaccharides from unfermented (JP) and fermented jackfruit pulp (JP-F). Furthermore, the physicochemical, structural, and bioactive properties of JP and JP-F were investigated. Results showed fermentation dropped the glucuronic acid, molecular weight, and particle size of JP-F by 15.62 %, 23.92 %, and 39.43 %, respectively, compared with those of JP. JP-F showed higher solubility than JP but lower apparent viscosity and thermal stability. Additionally, FT-IR spectra and X-ray diffraction analysis showed that fermentation did not alter the different types of glycosidic bonds and the fundamental polysaccharide structure. Moreover, JP-F exhibited stronger DPPH and ABTS free radical scavenging properties than JP and stronger stimulation on macrophage secretion of NO and IL-6 in RAW 264.7 cells. Therefore, using L. plantarum FM 17 for fermentation can alter physical and chemical properties of jackfruit pulp polysaccharides, enhancing their bioactivities.

Ultrasonic-microwave-assisted extraction for enhancing antioxidant activity of Dictyophora indusiata polysaccharides: The difference mechanisms between single and combined assisted extraction

The purpose of this study is to investigate the effects of different extraction methods (hot water-assisted extraction (HWE), microwave-assisted extraction (MAE), ultrasonic-assisted extraction (UAE), and ultrasonic-microwave- assisted extraction (UAME)) on the yield, chemical structures and antioxidant activity of Dictyophora indusiata polysaccharides (DPs). The research results showed that UMAE treatment had greater degree of damage to the cell wall of DPs and better comprehensive antioxidant capacity. Different extraction methods had no obvious effect on the types of glycosidic bonds and sugar rings, similar chemical composition and monosaccharide composition, with different absolute molecular weight (Mw) and molecular conformation. In particular, DPs for UMAE method had the highest polysaccharides yield, which was related to the conformational stretching and degradation avoidance of DPs in the higher molecular weight components under the simultaneous action of microwave and ultrasonic. These findings suggest that the UMAE technology has good potential for modification and application of DPs in the functional food industry.

Purification, Characterization and Bioactivities of Polysaccharides Extracted from Safflower (Carthamus tinctorius L.).

Polysaccharides are the main bioactive components in safflower. In this study, safflower polysaccharides (SPs) were extracted by ultrasonic assisted extraction, and four purified safflower polysaccharide fractions (named SSP1, SSP2, SSP3, and SSP4, respectively) were obtained. The physicochemical properties and in vitro physiological activities of the four fractions were investigated. The molecular weights (MW) of the SSPs were 38.03 kDa, 43.17 kDa, 54.49 kDa, and 76.92 kDa, respectively. Glucuronic acid, galactose acid, glucose, galactose, and arabinose were the main monosaccharides. The Fourier transform infrared spectroscopy (FT-IR) indicated that the polysaccharides had α- and β-glycosidic bonds. Nuclear magnetic resonance (NMR) analysis showed that SSP1 had 6 different types of glycosidic bonds, while SSP3 had 8 different types. SSP3 exhibited relatively higher ABTS+ scavenging activity, Fe+3-reduction activity, and antiproliferative activity. The results will offer a theoretical framework for the use of SPs in the industry of functional foods and medications.

Unexpected High-Substrate-Dependent Ketonization of Aldose on Niobium Phosphate-Supported Magnesia: An Emphasis on Surface Chemisorption

A water-tolerant magnesia-based solid base was prepared by combining the use of a non-equilibrium and highly structured dual-porous niobium phosphate (NbP) as the support and high-temperature thermal treatment. The crystal growth of MgO changed, and the bond length of Mg–O was longer than that of pure MgO after it was supported on NbP, which led to the higher basic property of O2– on the surface of MgO/NbP to act as a solid base catalyst toward aldose ketonization. It was revealed that the prepared solid base MgO/NbP exhibited high substrate dependence for ketonization of saccharides, facilitating the use of glucose and glucose-containing aldo-disaccharides─including maltose, cellobiose, lactose, and melibiose─due to their lower free energy after chemisorption than that of pentose, and a moderate reverse reaction barrier in aqueous solution. It was demonstrated that ketonization mainly occurred on the solid surface, especially in the case of high substrate concentration, which was different from the conventional opinion. The type of glycosidic bond and the constituent monosaccharides also affected the yield and selectivity of rare keto-disaccharides. The high performance of the MgO/NbP catalyst toward ketonization of disaccharides was realized as the typical yield and the productivity of maltulose reached 14.2% and 42.6 g·kg-solution–1·h–1, respectively, when treated with 30.0 wt % maltose solution at 130 °C. Although deactivation issues, such as leaching of ions and coke deposition, still remain to be solved, the catalyst has potential to be used in synthesizing high-value rare keto-disaccharides.

Preparation, characterization and bioactivities of selenized polysaccharides from Lonicera caerulea L. fruits

Native polysaccharide was obtained from Lonicera caerulea L. fruits (PLP). Two selenized polysaccharides (PSLP-1 and PSLP-2) were synthesized by the microwave-assisted HNO3-Na2SeO3 method, where the selenium (Se) contents were 228 ± 24 and 353 ± 36 μg/g, respectively. The molecular weights of PLP, PSLP-1, and PSLP-2 were 5.9 × 104, 5.6 × 104, and 5.1 × 104 kDa, respectively. PSLP-1 and PSLP-2 contained the same type of monosaccharides as PLP but with different molar ratios. The main chain structure of the native polysaccharide was not changed after selenization. PLP, PSLP-1, and PSLP-2 contained the same six types of glycosidic bonds. Bioactivity assays revealed that the two selenized polysaccharides possessed better antioxidant activities than PLP, but their bile acid-binding abilities and inhibitory activities on acetylcholinesterase (AChE) had weakened. In summary, PLP, PSLP-1, and PSLP-2 may be promising Se supplements in functional foods and inhibitors for the treatment of AChE.

Exploring the novel mechanistic aspects of function of a hyperthermophile two‐site exo‐amylase‐cum‐glucanotransferase displaying substrate versatility

We have recently described an exo‐amylase‐cum‐glucanotransferase, PfuAmyGT, from Pyrococcus furiosuswhich uses disproportionation to generate a pool of glucose and small malto‐oligosaccharides (MOGs) from starch, or from any single MOG (or a combination of MOGs). PfuAmyGT appears to use a combination of exo‐amylase action and excision‐and‐transfer of glucose from donor to acceptor MOGs, using a unique and novel mechanism involving two catalytically‐active sites (i.e., separate donor and acceptor sites, with a loop transferring the excised glucose) in place of the more common single site (at which the donated glucose is excised, and left, by the departing donor MOG, for being picked up by the acceptor MOG). We demonstrate that there are five residues (three glutamates and two aspartates) that are essential for activity, suggesting that different acidic side chains act at the donor and acceptor sites. We also demonstrate that PfuAmyGT acts upon substrates possessing different monomeric units and different types of glycosidic bonds (e.g., pectin, xylan or cellulose), indicating an unprecedented level of versatility, given that only one other glycosyl hydrolase (a neo‐pullulanase) has previously been reported to act upon more than one type of glycosidic bond (alpha‐1,4 and alpha‐1,6). Our bioinformatics and biochemical analyses suggest that the donor site of PfuAmyGT is processive, while the acceptor site releases and rebinds MOGs in each duty cycle. We have identified a total of six residues in the vicinity of a catalytic aspartate (D362) that potentially function to give rise to the said substrate versatility. Four of the six residues are also catalytically important for the functioning of PfuAmyGT on different substrates.

Screening of probiotics with efficient α-glucosidase inhibitory ability and study on the structure and function of its extracellular polysaccharide

Inhibition of α-glucosidase activity is an important strategy in lowering the concentration of blood sugar. In this paper, using domestic and foreign characteristic food-derived substances as the sources of lactobacillus, the performance of them were evaluated by measuring the strains’ α-glucosidase inhibitory ability. Finally, the cell-free extracellular supernatants (CFS) of Lactobacillus rhamnosus LB1lac10 was determined to have the highest α-glucosidase inhibition ability. Based on the Nanopore third-generation sequencing technology platform, the genome of LB1lac10 was sequenced and functional gene annotation was performed. After that, the biological activity and structural composition of the exopolysaccharide produced by L. rhamnosus LB1lac10 were studied. The purified exopolysaccharide EPS1-1 also showed efficient α-glucosidase inhibitory ability. The structure and conformation characteristics of EPS1-1 were further analyzed. The EPS1-1 from L. rhamnosus LB1lac10 had a molecular weight of 88,650 Da, and it was mainly composed of mannose, glucuronic acid, glucose, xylose, galactose, and arabinose. From the FT-IR and NMR analyses, EPS1-1 had functional groups of a typical polysaccharide structure and contained two types of glycosidic bonds with α-configuration pyranose. The main glycosidic bond corresponded to → 4)-α- d-Glcp-(1→, which might be an important reason why EPS1-1 could inhibit α-glycosidase. Thermodynamic studies showed that EPS1-1 had high heat resistance to meet the needs of food processing. The results suggested that L. rhamnosus LB1lac10 could be used as a potential probiotic to lower blood sugar, and the EPS1-1 has the potential to serve as a natural α-glycosidase inhibitor to regulate the concentration of blood glucose.

Establishing a kinetic model of biomass-derived disaccharide hydrolysis over solid acid: A case study on hierarchically porous niobium phosphate

Macroscopic kinetic models were established to describe the overall hydrolysis process of disaccharides with different type of glycosidic bond and constituted monosaccharides over hierarchically porous niobium phosphate (NbP) aiming for evaluating reaction efficiency of saccharide hydrolysis over solid acid. The NbP sample was synthesized by a sol–gel method accompanied by phase separation with co-continuous macroporous structure and high P/Nb molar ratio. The synthesized NbP sample showed high catalytic performance in the hydrolysis of disaccharides in an aqueous solution. Sucrose with α(1 → 2) glycosidic bond was the most easily hydrolyzed, with almost 100% conversion and monosaccharide yield, followed by melibiose α(1 → 6) and maltose α(1 → 4), while cellobiose β(1 → 4) was the strongest against to be hydrolyzed. The kinetic analysis showed that the reaction order is 1.0 over all the substrates and varied from 0.45 to 0.82 over the acid site, depending on the type of disaccharide. The activation of the decomposition reaction was larger than that of hydrolysis reaction, indicating that decomposition is more sensitive to temperature change than hydrolysis. Accordingly, direct decomposition of the disaccharides and the constituent monosaccharides synergistically determined the final yield and selectivity of the monosaccharides. Further, the decomposition and dehydration of glucose and galactose were found to occur in the bulk aqueous solution instead of on the surface of NbP.

Cunninghamella echinulata PA3S12MM invertase: Biochemical characterization of a promiscuous enzyme.

The Cunninghamella echinulata PA3S12MM fungus is a great producer of invertases in a growth medium supplemented by apple peels. The enzyme was purified 4.5 times after two chromatographic processes, and it presented a relative molecular mass of 89.2kDa. The invertase reached maximum activity at pH of 6 and at 60°C, in addition to presenting stability in alkaline pH and thermal activation at 50°C. The enzymatic activity increased in the presence of Mn2+ and dithiothreitol (DTT), while Cu2+ and Z2+ ions inhibited it. Also, DTT showed to protect enzymatic activity. The apparent values for Km , Vmáx , and Kcat for the sucrose hydrolysis were, respectively, 173.8mmol/L, 908.7mmol/Lmin-1 , and 1,388.79s-1 . The carbohydrate content was of 83.13%. The invertase presented hydrolytic activity over different types of glycosidic bonds, such as α1↔2β (sucrose), α1→4 (polygalacturonic acid), α1→4 and α1→2 (pectin), and α1↔1 (trehalose), indicating that the enzyme is multifunctional. Thus, the biochemical properties showed by the C. echinulata PA3S12MM suggest a broad industrial application, such as in the biomass hydrolysis or in the food industry. PRACTICAL APPLICATIONS: Invertases are hydrolytic enzymes employed in several industrial sectors. Given their great importance for the economy and several industrial sectors, there is a growing interest in microorganisms producing this enzyme. The analysis of the biochemical properties of invertase in C. echinulata PA3S12MM suggest applications in the food industry. Due to its increased hydrolytic activity, the hydrolysis process of the sucrose may employ invertase for the production of invert sugar. The stability at alkaline pH suggests an application in the development of enzymatic electrodes for the quantification of sucrose in food and beverage. The multifunctional activity may work in the biomass hydrolysis or saccharification of by-products for the extraction of fermentable sugars. The high level of invertase N-linked glycosylation of invertase grants this enzyme thermal stability at high temperatures, in addition to resistance against the action of proteases, which are desirable characteristics for the application of this enzyme in industrial processes.

O-/N-/S-Specificity in Glycosyltransferase Catalysis: From Mechanistic Understanding to Engineering

Glycosyltransferases (GTs) catalyze the formation of glycosidic bonds in carbohydrates and glycoconjugates, with various outcomes depending not only on the acceptor molecules they bind but also on the type of glycosidic bond they form (C–O, C–N, C–S, or C–C). Here we show that the glucosyltransferase UGT1 from the indigo plant Polygonum tinctorium catalyzes either N-, O-, or S-glycosylation with similar rates. We solve the structure of the enzyme in complex with its donor and acceptor substrates and elucidate the molecular basis of N-, O-, and S-specificities using experimental mutagenesis and QM/MM simulations, revealing distinct mechanisms for N-, O-, and S-glycosylation. We also show that the active site can be engineered to increase or favor one of the three glycosylation activities over another. These results will foster the design of more active and specific enzyme variants for production of glycosides.

Comparison of the experimental and theoretical production of biogas by monosaccharides, disaccharides, and amino acids

The estimation of biogas production from organic monomers is very important for the optimal design, configuration, and efficient evaluation of the anaerobic digestion processes in a digester. The theoretical estimation of the biogas potential that is most used is that of Buswell and Boyle. In this work, we found that this estimate was much exaggerated compared to the real biogas potential determined in practice. For monosaccharides, we noted that the biogas potential of glucose was very low compared to that of fructose, even though the two substrates have the same chemical composition and molecular mass. The same result was observed for the disaccharides lactose and maltose. The amino acid valine produced more biogas than the amino acid cysteine did. The experimental potential remained lower than the calculated potential. An important difference existed between the experimental biogas potential of the six monomers investigated and the theoretical biogas potential. This indicated that the calculation of the biogas potential by the stereochemical equation of Buswell and Boyle was overstated and did not take into consideration the isometric form, spatial configuration, and intermediate metabolite produced by the monosaccharides in the four steps of anaerobic digestion. For the disaccharides, the theoretical calculations did not take into account the nature of the molecular components in carbohydrate, type of glycosidic bond, and intermediate metabolites of substrates for anaerobic digestion. Finally, for the amino acids, it does not take into account the ramification of the atomic components and the chemical nature of atoms in amino acids.

Activity-guided isolation, identification and quantification of biologically active isomeric compounds from folk medicinal plant Desmodium adscendens using high performance liquid chromatography with diode array detector, mass spectrometry and multidimentional nuclear magnetic resonance spectroscopy

The antioxidant activity of the crude extract (60% ethanol) from the leaves of Desmodium adscendens (Sw.) DC. (Fabaceae) was observed in DPPH, xanthine/xanthine oxidase, lipid peroxydation and neutrophils burst tests. Further activity-guided fractionation on C18 column (water, 20% methanol, 50% methanol and 100% methanol) resulted in the separation of the fraction (50% methanol) with the highest antioxidant capacity. HPLC-DAD analysis of biologically active fraction revealed the presence of two pairs of flavonoid isomers as the dominant constituents. Those compounds were isolated and purified by multi-step liquid column chromatography (Sephadex LH20). Their structures were elucidated by various spectroscopic techniques, including NMR, UV and MS. Based on 1D and 2D NMR spectra as well as ion fragmentation, flavonoids were identified as: isovitexin 2″-O-xyloside (1), vitexin 2″-O-xyloside (2), vitexin (3) and isovitexin (4). The hybrid HSQC-DEPT technique provided very fast determination of the glycosylation positions in aglycone and the type of glycosidic bond in the flavonoid isomers. This study provides novel information concerning identity of the major compounds present in the leaves of D. adscendens cultivated in Ghana, which broadens the knowledge about anti-inflammatory, antiallergic and antioxidant properties of their extracts.

Noncatalytic Hydrothermal Elimination of the Terminal d-Glucose Unit from Malto- and Cello-Oligosaccharides through Transformation to d-Fructose

Noncatalytic hydrothermolyses of malto- and cello-oligosaccharides (di-, tri-, tetraose), linked by α- and β-1,4-glycosidic bonds, respectively, were investigated at 100-140 °C. In situ (13)C NMR spectroscopy was applied to elucidate the position and pathways of the glycosidic bond breakage and the dependence of the hydrolysis rate on the bond type. Spectral analysis was carried out quantitatively as a function of time with the mass balance confirmed, and it was shown for both the malto- and the cello-oligosaccharides that the terminal D-glucose unit with a free anomeric carbon is selectively eliminated after transformation to D-fructose. Site-selective breakage of the glycosidic bonds proceeded on the order of hours. The initial apparent rates for terminal hydrolysis were found to be independent of the degree of oligomerization but dependent on the type of glycosidic bond. Rate constants were larger for the α-1,4-linked malto-oligosaccharides by a factor of 3-4 than for the β-1,4-linked cello-oligosaccharides. The pathways and mechanisms for the malto- and cello-oligosaccharide hydrothermolyses are common and can be understood in terms of the elementary reactions of the di- and monosaccharides.

Deconjugation and Degradation of Flavonol Glycosides by Pig Cecal Microbiota Characterized by Fluorescence in Situ Hybridization (FISH)

As the bioavailability of flavonoids is influenced by intestinal metabolism, we have investigated the microbial deconjugation and degradation of several flavonols and flavonol glycosides using the pig cecum in vitro model system developed in our group. For this model system the microbiota was directly isolated from the cecal lumen of freshly slaughtered pigs. The characterization of the cecal microbiota by fluorescence in situ hybridization (FISH) with 16S rRNA-based oligonucleotide probes confirmed the suitability of the model system for studying intestinal metabolism by the human microbiota. We have investigated the microbial degradation of quercetin-3-O-beta-d-rutinoside 1, quercetin-3-O-beta-d-glucopyranoside 2, quercetin-4'-O-beta-d-glucopyranoside 3, quercetin-3-O-beta-d-galactopyranoside 4, quercetin-3- O-beta-d-rhamnopyranoside 5, quercetin-3- O-[alpha-l-dirhamnopyranosyl-(1-->2)-(1-->6)-beta-d-glucopyranoside 6, kaempferol-3-O-[alpha-l-dirhamnopyranosyl-(1-->2)-(1-->6)-beta-d-glucopyranoside 7, apigenin 8, apigenin-8- C-glucoside (vitexin) 9, and feruloyl-O-beta-d-glucopyranoside 10 (100 microM), representing flavonoids with different aglycones, sugar moieties, and types of glycosidic bonds. The degradation rate was monitored using HPLC-DAD. The flavonol O-glycosides under study were almost completely metabolized by the intestinal microbiota within 20 min and 4 h depending on the sugar moiety and the type of glycosidic bond. The degradation rates of the quercetin monoglycosides showed a clear dependency on the hydroxyl pattern of the sugar moiety. The degradation of 2 with all hydroxyl groups of the glucose in the equatorial position was the fastest. The intestinal metabolism of di- and trisaccharides was much slower compared to the monoglycosides. The structure of the aglycone has not much influence on the intestinal metabolism; however, the type of glycosidic bond ( C- or O-glycoside) has substantial influence on the degradation rate. The liberated aglycones were completely metabolized within 8 h. Phenolic compounds such as 3,4-dihydroxyphenylacetic acid 12, 4-hydroxyphenylacetic acid 13, and phloroglucinol 18 were detected by GC-MS as main degradation products.

Polysaccharides of brown seaweeds X. The structure of the side chains of the pelvecyan molecule

The compositions and structures of some oligosaccharides isolated by the partial acid hydrolysis and acetolysis of pelvecyan have been established. It has been shown that the side chains of the pelvecyan molecule consist of residues of fucose, xylose, and galactose connected with one another in various sequences and by various types of glycosidic bonds.

鯨鼻軟骨ケラト硫酸の酵素分解-II.

The properties of a keratosulfate-degrading enzyme derived from an enteric bacterium was investigated. The enzyme activity was optimal between pH 5.0 and 6.0, and at about 50°C. The enzyme exhibited complete specificity for keratosulfate, and did not hydrolyze hyaluronic acid, chondroitin 4-sulfate and 6-sulfate or heparin. Several inorganic compounds such as sodium, potassium, magnesium and calcium chlorides and mucopolysaccharides such as chondroitin 6-sulfate and heparin had no significant effect on the enzyme activity in the range of concentrations tested. The MICHAELIS constant value for bovine cornea keratosulfate was 1.9 mg per ml. In order to see what type of glycosidic bond in keratosulfate is attacked by the enzyme, the degraded products of bovine cornea keratosulfate were isolated by Sephadex filtration, and their structures were determined by means of chemical analysis, sodium borohydride reduction and the enzymatic treatment with β-N-acetylglucosaminidase. Judging from the results, the products were di-, tetrasaccharides and larger oligosaccharides, which had a galactose moiety on their reducing ends. Thus, it was concluded that this enzyme is an endo.poly-β-galactosidase.