Search Results (8)

As an important component of N-linked glycoproteins, the core pentasaccharide is highly crucial to the potential application prospect of glycoprotein. However, the gas phase conformation study is a challenging one due to the size and complexity of the molecule, together with the necessity to rely on quantum chemistry modeling for relevant energetics and structures. In this paper, the structures of the trisaccharides and core pentasaccharides in N-linked glycans in the gas phase were constructed by a three-step tree-based (TSTB) sampling. Since single point energies of all the conformers are calculated at the temperature of zero, it is necessary to evaluate the stability at a high temperature. We calculate the Gibbs free energies using the standard thermochemistry model (T = 298.15 K). For trimannose, the energetic ordering at 298.15 K can be strongly changed compared to 0 K. Moreover, two structures of trimannose with high energies at 0 K are considered to provide a much better match of IR vibration signatures with the low Gibbs free energies. On this basis, the core pentasaccharide was constructed in three ways. The building configurations of core pentasaccharide were optimized to obtain reasonable low-energy stable conformers. Fortunately, the lowest-energy structure of core pentasaccharide is eventually the minimum at 0 K and 298.15 K. Furthermore, spectrum analysis of core pentasaccharide was carried out. Although poorly resolved, its contour from the experiment was in qualitative correspondence with the computed IR spectrum associated with its minimum free energy structure. A large number of strongly and weakly hydrogen-bonded hydroxyl and acetylamino groups contribute to a highly congested set of overlapping bands. Compared with traditional conformation generators, the TSTB sampling is employed to efficiently and comprehensively obtain preferred conformers of larger saccharides with lower energy. Full article

Epithelial cells can undergo apoptosis by manipulating the balance between pro-survival and apoptotic signals. In this work, we show that TRAIL-induced apoptosis can be differentially regulated by the expression of α(1,6)fucosyltransferase (FucT-8), the only enzyme in mammals that transfers the α(1,6)fucose residue to the pentasaccharide core of complex N-glycans. Specifically, in the cellular model of colorectal cancer (CRC) progression formed using the human syngeneic lines SW480 and SW620, knockdown of the FucT-8-encoding FUT8 gene significantly enhanced TRAIL-induced apoptosis in SW480 cells. However, FUT8 repression did not affect SW620 cells, which suggests that core fucosylation differentiates TRAIL-sensitive premetastatic SW480 cells from TRAIL-resistant metastatic SW620 cells. In this regard, we provide evidence that phosphorylation of ERK1/2 kinases can dynamically regulate TRAIL-dependent apoptosis and that core fucosylation can control the ERK/MAPK pro-survival pathway in which SW480 and SW620 cells participate. Moreover, the depletion of core fucosylation sensitises primary tumour SW480 cells to the combination of TRAIL and low doses of 5-FU, oxaliplatin, irinotecan, or mitomycin C. In contrast, a combination of TRAIL and oxaliplatin, irinotecan, or bevacizumab reinforces resistance of FUT8-knockdown metastatic SW620 cells to apoptosis. Consequently, FucT-8 could be a plausible target for increasing apoptosis and drug response in early CRC. Full article

The structural characterization of lipopolysaccharides has critical implications for some biomedical applications, and marine bacteria are an inimitable source of new glyco-structures potentially usable in medicinal chemistry. On the other hand, lipopolysaccharides of marine Gram-negative bacteria present certain structural features that can help the understanding of the adaptation processes. The deep-sea marine Gram-negative bacterium Idiomarina zobellii KMM 231^T, isolated from a seawater sample taken at a depth of 4000 m, represents an engaging microorganism to investigate in terms of its cell wall components. Here, we report the structural study of the R-type lipopolysaccharide isolated from I. zobellii KMM 231^T that was achieved through a multidisciplinary approach comprising chemical analyses, NMR spectroscopy, and MALDI mass spectrometry. The lipooligosaccharide turned out to be characterized by a novel and unique pentasaccharide skeleton containing a very short mono-phosphorylated core region and comprising terminal neuraminic acid. The lipid A was revealed to be composed of a classical disaccharide backbone decorated by two phosphate groups and acylated by i13:0(3-OH) in amide linkage, i11:0 (3-OH) as primary ester-linked fatty acids, and i11:0 as a secondary acyl chain. Full article

In the animal kingdom, a stunning variety of N-glycan structures have emerged with phylogenetic specificities of various kinds. In the plant kingdom, however, N-glycosylation appears to be strictly conservative and uniform. From mosses to all kinds of gymno- and angiosperms, land plants mainly express structures with the common pentasaccharide core substituted with xylose, core α1,3-fucose, maybe terminal GlcNAc residues and Lewis A determinants. In contrast, green algae biosynthesise unique and unusual N-glycan structures with uncommon monosaccharides, a plethora of different structures and various kinds of O-methylation. Mosses, a group of plants that are separated by at least 400 million years of evolution from vascular plants, have hitherto been seen as harbouring an N-glycosylation machinery identical to that of vascular plants. To challenge this view, we analysed the N-glycomes of several moss species using MALDI-TOF/TOF, PGC-MS/MS and GC-MS. While all species contained the plant-typical heptasaccharide with no, one or two terminal GlcNAc residues (MMXF, MGnXF and GnGnXF, respectively), many species exhibited MS signals with 14.02 Da increments as characteristic for O-methylation. Throughout all analysed moss N-glycans, the level of methylation differed strongly even within the same family. In some species, methylated glycans dominated, while others had no methylation at all. GC-MS revealed the main glycan from Funaria hygrometrica to contain 2,6-O-methylated terminal mannose. Some mosses additionally presented very large, likewise methylated complex-type N-glycans. This first finding of the methylation of N-glycans in land plants mirrors the presumable phylogenetic relation of mosses to green algae, where the O-methylation of mannose and many other monosaccharides is a common trait. Full article

Plesiomonas shigelloides is a Gram-negative, rod-shaped bacterium which causes foodborne intestinal infections, including gastroenteritis. It is one of the most frequent causes of travellers’ diarrhoea. Lipopolysaccharide (LPS, endotoxin), an important virulence factor of the species, is in most cases characterised by a smooth character, demonstrated by the presence of all regions, such as lipid A, core oligosaccharide, and O-specific polysaccharide, where the latter part determines O-serotype. P. shigelloides LPS is still a poorly characterised virulence factor considering a “translation” of the particular O-serotype into chemical structure. To date, LPS structure has only been elucidated for 15 strains out of 102 O-serotypes. Structures of the new O-specific polysaccharide and core oligosaccharide of P. shigelloides from the Czechoslovak National Collection of Type Cultures CNCTC 90/89 LPS (O22), investigated by chemical analysis, mass spectrometry, and ¹H,¹³C nuclear magnetic resonance (NMR) spectroscopy, have now been reported. The pentasaccharide repeating unit of the O-specific polysaccharide is built of one d-QuipNAc and is rich in four d-GalpNAcAN residues. Moreover, the new core oligosaccharide shares common features of other P. shigelloides endotoxins, i.e., the lack of phosphate groups and the presence of uronic acids. Full article

Whooping cough is a highly contagious disease caused predominantly by Bordetella pertussis, but it also comprises of a pertussis-like illness caused by B. holmesii. The virulence factors of B. holmesii and their role in the pathogenesis remain unknown. Lipopolysaccharide is the main surface antigen of all Bordetellae. Data on the structural features of the lipopolysaccharide (LPS) of B. holmesii are scarce. The poly- and oligosaccharide components released by mild acidic hydrolysis of the LPS were separated and investigated by ¹H and ¹³C NMR spectroscopy, mass spectrometry, and chemical methods. The structures of the O-specific polysaccharide and the core oligosaccharide of B. holmesii ATCC 51541 have been identified for the first time. The novel pentasaccharide repeating unit of the B. holmesii O-specific polysaccharide has the following structure: {→2)-α-l-Rhap-(1→6)-α-d-Glcp-(1→4)-[β-d-GlcpNAc-(1→3]-α-d-Galp-(1→3)-α-d-GlcpNAc-(1→}_n. The SDS-PAGE and serological cross-reactivities of the B. holmesii LPS suggested the similarity between the core oligosaccharides of B. holmesii ATCC 51541 and B. pertussis strain 606. The main oligosaccharide fraction contained a nonasaccharide. The comparative analysis of the NMR spectra of B. holmesii core oligosaccharide fraction with this of the B. pertussis strain 606 indicated that the investigated core oligosaccharides were identical. Full article

We have isolated a novel lectin, named HRL40 from the green alga Halimeda renschii. In hemagglutination-inhibition test and oligosaccharide-binding experiment with 29 pyridylaminated oligosaccharides, HRL40 exhibited a strict binding specificity for high-mannose N-glycans having an exposed (α1-3) mannose residue in the D2 arm of branched mannosides, and did not have an affinity for monosaccharides and other oligosaccharides examined, including complex N-glycans, an N-glycan core pentasaccharide, and oligosaccharides from glycolipids. The carbohydrate binding profile of HRL40 resembled those of Type I high-mannose specific antiviral algal lectins, or the Oscillatoria agardhii agglutinin (OAA) family, which were previously isolated from red algae and a blue-green alga (cyanobacterium). HRL40 potently inhibited the infection of influenza virus (A/H3N2/Udorn/72) into NCI-H292 cells with half-maximal effective dose (ED₅₀) of 2.45 nM through high-affinity binding to a viral envelope hemagglutinin (K_D, 3.69 × 10⁻¹¹ M). HRL40 consisted of two isolectins (HRL40-1 and HRL40-2), which could be separated by reverse-phase HPLC. Both isolectins had the same molecular weight of 46,564 Da and were a disulfide -linked tetrameric protein of a 11,641 Da polypeptide containing at least 13 half-cystines. Thus, HRL40, which is the first Type I high-mannose specific antiviral lectin from the green alga, had the same carbohydrate binding specificity as the OAA family, but a molecular structure distinct from the family. Full article

Six pentasaccharide resin glycosides from Ipomoea cairica, including four new acylated pentasaccharide resin glycosides, namely cairicoside I–IV (1–4) and the two known compounds cairicoside A (5) and cairicoside C (6), were isolated from the aerial parts of Ipomoea cairica. Their structures were established by a combination of spectroscopic, including two dimensional (2D) NMR and chemical methods. The core of the six compounds was simonic acid A, and they were esterfied the same sites, just differing in the substituent groups. The lactonization site of the aglycone was bonded to the second saccharide moiety at C-2 in 1–4, and at C-3 in 5–6. Compounds 1 and 5, 4 and 6 were two pairs of isomers. The absolute configuration of the aglycone in 1–6 which was (11S)-hydroxyhexadecanoic acid (jalapinolic acid) was established by Mosher’s method. Compounds 1–4 have been evaluated for inhibitory activity against α-glucosidase, which all showed inhibitory activities. Full article