Structural elucidation of the capsular polysaccharide from Streptococcus pneumoniae serotype 47A by NMR spectroscopy

Diversity of sugar-diphospholipid-utilizing glycosyltransferase families

Peptidoglycan polymerases, enterobacterial common antigen polymerases, O-antigen ligases, and other bacterial polysaccharide polymerases (BP-Pols) are glycosyltransferases (GTs) that build bacterial surface polysaccharides. These integral membrane enzymes share the particularity of using diphospholipid-activated sugars and were previously missing in the carbohydrate-active enzymes database (CAZy; www.cazy.org ). While the first three classes formed well-defined families of similar proteins, the sequences of BP-Pols were so diverse that a single family could not be built. To address this, we developed a new clustering method using a combination of a sequence similarity network and hidden Markov model comparisons. Overall, we have defined 17 new GT families including 14 of BP-Pols. We find that the reaction stereochemistry appears to be conserved in each of the defined BP-Pol families, and that the BP-Pols within the families transfer similar sugars even across Gram-negative and Gram-positive bacteria. Comparison of the new GT families reveals three clans of distantly related families, which also conserve the reaction stereochemistry.

Structure analysis and antioxidant activity of polysaccharide-iron (III) from Cordyceps militaris mycelia

Iron-enriched Cordyceps militaris was obtained by adding FeSO₄ solution to the mycelia for biotransformation. The polysaccharide-iron (III) was extracted by water extraction and alcohol precipitation. High performance liquid chromatography showed that the crude polysaccharide-iron (III) had three components. The second component was purified by Sephadex G-150 and named as CPS-iron-II. The average molecular weight of CPS-iron-II was 44.136 kDa. The content of iron was 2.73%. The monosaccharide composition analysis indicated that the CPS-iron-II was composed of rhamnose, arabinose, galactose, glucose, mannose, galacturonic acid with percentage ratio of 0.94:3.12:27.01:36.62:30.20:2.12. The results of methylation analysis revealed that the CPS-iron-II was made of →2)-β-D-Glcp-(1→, with →2, 4)-α-D-Glcp-(1→ highly branched. Congo-red test showed that CPS-iron-II can cause flocculation of Congo red solution. The anti-oxidative analysis showed that antioxidant activity of CPS-iron-II was almost equal to that of Vc. The manuscript provided a new way for the preparation of polysaccharide-iron(III) from Cordyceps militaris.

Structural characterization of fucose-containing disaccharides prepared from exopolysaccharides of Enterobacter sakazakii

Fucose-containing oligosaccharides (FCOs) have important applications in the food, medicine, and cosmetics industries owing to their unique biological activities. The degradation of microbial fucose-containing exopolysaccharide (FcEPS) is a promising strategy for obtaining FCOs, and bacteriophage-borne glycanase is a useful tool for degrading FcEPS. Here, we aimed to obtain FCOs using bacteriophage-borne glycanase to depolymerize FcEPS from Enterobacter sakazakii. The FcEPS was mainly composed of l-fucose (42.72 %), d-galactose (20.59 %), and d-glucose (21.81 %). Based on the results of nuclear magnetic resonance and mass spectrometry, the obtained FCOs were disaccharide fragments with backbones of β-d-Glcp-(1→4)-β-l-Fucp and α-d-Galp-(1→3)-β-l-Fucp, respectively. So far, few studies of disaccharides prepared from FcEPS have been reported. This study demonstrated that the FcEPS of E. sakazakii was a reliable fucose-containing disaccharide source and that bacteriophage-borne glycanase was an effective degradation tool for obtaining FCOs fragments from FcEPS.

Chemical structure and antioxidant activity of a polysaccharide from Siraitia grosvenorii

A novel polysaccharide from Siraitia grosvenorii residues (SGP, molecular weight 1.93 × 10³ KDa) was isolated and purified. SGP was composed of α-L-Arabinose, α-D-Mannose, α-d-Glucose, α-D-Galactose, Glucuronic acid, and Galacturonic acid with the ratio of 1: 1.92: 3.98: 7.63: 1.85: 7.34. The backbone of SGP was consist of galactoses and linked by α-(1,4)-glycosidic bond. The branch chains including α-1,6 linked glucose branch, α-1,6 linked mannose branch, α-1,3 linked galactose branch and arabinose branched (α-L-Ara(1→). The results of bioactivity experiments suggested that SGP had antioxidant in vitro, especially on scavenging DPPH radicals. Besides, SGP resulted in the decrease of ROS and the percentage of apoptotic and necrotic cells in a dose-dependent manner in H₂O₂ oxide injury PC12 cells. This research could help to develop the potential value and utilization of Siraitia grosvenorii.

Pneumococcal Capsules and Their Types: Past, Present, and Future

Streptococcus pneumoniae (the pneumococcus) is an important human pathogen. Its virulence is largely due to its polysaccharide capsule, which shields it from the host immune system, and because of this, the capsule has been extensively studied. Studies of the capsule led to the identification of DNA as the genetic material, identification of many different capsular serotypes, and identification of the serotype-specific nature of protection by adaptive immunity. Recent studies have led to the determination of capsular polysaccharide structures for many serotypes using advanced analytical technologies, complete elucidation of genetic basis for the capsular types, and the development of highly effective pneumococcal conjugate vaccines. Conjugate vaccine use has altered the serotype distribution by either serotype replacement or switching, and this has increased the need to serotype pneumococci. Due to great advances in molecular technologies and our understanding of the pneumococcal genome, molecular approaches have become powerful tools to predict pneumococcal serotypes. In addition, more-precise and -efficient serotyping methods that directly detect polysaccharide structures are emerging. These improvements in our capabilities will greatly enhance future investigations of pneumococcal epidemiology and diseases and the biology of colonization and innate immunity to pneumococcal capsules.

Structural characteristics of pineapple pulp polysaccharides and their antitumor cell proliferation activities

BACKGROUND

Pineapple has a delicious taste and good health benefits. Bioactive polysaccharides are important components of pineapple that might contribute to its health benefits. Since little structural information on these polysaccharides is currently available, the aim of this study was to investigate their structural characteristics and bioactivities.

RESULTS

The polysaccharides of pineapple pulp were fractionated into three fractions (PAPs 1-3) by anion exchange chromatography. Their structural characteristics were first identified, including molecular weights and glycosidic linkages. The monosaccharide compositions were revealed as PAP 1 (Ara, Xyl, Man, Glc and Gal), PAP 2 (Rha, Ara, Xyl, Man, Glc and Gal) and PAP 3 (Rha, Ara, Xyl, Man and Gal). Nuclear magnetic resonance (NMR) spectra suggested that PAP 2 had a backbone of → 4)-α-d-Manp-(1 → 2,4)-α-d-Manp-(1 → with branches attached to O-4 of Manp. The NMR data of α-l-Araf-(1→, →3)-α-l-Araf-(1→, →4)-β-d-Galp-(1 → and → 4)-α-d-GalpAMe-(1 → were assigned. PAPs 1 and 2 showed significant antitumor cell proliferation activities against breast carcinoma cell line and strong antioxidant activities.

CONCLUSION

The above findings indicated that PAPs 1-3 contributed much to the health benefits of pineapple. They could be used as health-beneficial food additives in functional foods.

Low invasiveness of pneumococcal serotype 11A is linked to ficolin-2 recognition of O-acetylated capsule epitopes and lectin complement pathway activation

BACKGROUND

The divergent epidemiological behavior of Streptococcus pneumoniae serotypes suggests that serotype-specific features such as capsule O-acetylation influence the propensity of a strain to cause invasive pneumococcal disease (IPD). We hypothesize that innate host factors mediate the observed negative association between IPD and the serotype 11A (ST11A) capsule O-acetyltransferase gene, wcjE.

METHODS

We evaluated the ability of ficolin-2, an initiator of the lectin complement pathway that was previously shown to bind ST11A pneumococci, to recognize and mediate complement-dependent opsonophagocytosis of different pneumococcal serotypes. We supplemented findings with an epidemiological meta-analysis comparing invasiveness of the 30 most prevalent pneumococcal serotypes.

RESULTS

Ficolin-2 bound ST11A capsule polysaccharide and other wcjE-containing pneumococcal serotypes, except ST9V and ST20B. Ficolin-2 did not bind wcjE-null serotypes, including the wcjE-null variant of ST11A, ST11E. We observed C1q-independent complement deposition and phagocytic killing of pneumococci expressing ST11A but not those expressing ST11E. Inhibition of ficolin-2 binding abrogated ST11A-associated complement deposition and phagocytosis. In children, invasiveness of ST11A was the lowest among serotypes tested in our meta-analysis, while ST9V was among the highest.

CONCLUSIONS

Ficolin-2 mediates serum protection by recognizing specific O-acetylated epitopes of pneumococcal capsule polysaccharides, exemplifying a novel host-microbe interaction that innately offers serotype-specific immunity to IPD.

Structural determination of Streptococcus pneumoniae repeat units in serotype 41A and 41F capsular polysaccharides to probe gene functions in the corresponding capsular biosynthetic loci

We report the repeating unit structures of the native capsular polysaccharides of Streptococcus pneumoniae serotypes 41A and 41F. Structural determinations yielded six carbohydrate units in the doubly branched repeating unit to give the following structure for serotype 41A: The structure determinations were motivated (1) by an ambition to help close the remaining gaps in S. pneumoniae capsular polysaccharide structures, and (2) by the attempt to derive functional annotations of carbohydrate active enzymes in the biosynthesis of bacterial polysaccharides from the determined structures. An activity present in 41F but not 41A is identified as an acetyltransferase acting on the rhamnopyranosyl sidechain E. The genes encoding the formation of the six glycosidic bonds in serogroup 41 were determined from the capsular polysaccharide structures of serotype 41A, 41F, and genetically related serotypes, in conjunction with corresponding genomic information and computational homology searches. In combination with complementary information, NMR spectroscopy considerably simplifies the functional annotation of carbohydrate active enzymes in the biosynthesis of bacterial polysaccharides.

Chemical structures of Streptococcus pneumoniae capsular polysaccharide type 39 (CPS39), CPS47F, and CPS34 characterized by nuclear magnetic resonance spectroscopy and their relation to CPS10A

Structural characterization of Streptococcus pneumoniae capsular polysaccharides (CPS) is a prerequisite for unraveling both antigenic and genetic relationships that exist between different serotypes. In the current study, comparative structural studies of S. pneumoniae CPS serogroup 10 (CPS10) were extended to include genetically related S. pneumoniae CPS34, CPS39, and CPS47F. High-resolution heteronuclear nuclear magnetic resonance (NMR) spectroscopy confirmed the published structure of CPS34 and, in conjunction with glycosyl composition analyses, revealed the following repeat unit structures of the other serotypes, which have not been previously characterized: [structure: see text] Common and unique structural features of these polysaccharides, including different positions of O-acetylation, were unambiguously associated with specific genes in each corresponding cps locus. The only exception involved the gene designated wcrC, which is associated with the α1-2 transfer of Gal pyranoside (Galp) to ribitol-5-phosphate in the synthesis of CPS10A, CPS47F, and CPS34 but with α1-1 transfer of Gal to ribitol-5-phosphate in the synthesis of CPS39. The corresponding gene in the cps39 locus, although related to wcrC, more closely resembled a previously identified gene (i.e., wefM) of Streptococcus oralis that is associated with α1-1 transfer of Galp to ribitol-5-phosphate. These and other recent findings identify linkages from α-Galp to ribitol-5-phosphate and from this residue to adjacent Gal furanoside (Galf) as important sites of CPS structural and genetic diversity.

Determination of native capsular polysaccharide structures of Streptococcus pneumoniae serotypes 39, 42, and 47F and comparison to genetically or serologically related strains

The diversity of capsular polysaccharides of the bacterial pathogen Streptococcus pneumoniae leads to at least 91 different serotypes. While the genetic loci for capsular biosynthesis have been characterized for all serotypes, the determination of resultant polysaccharide structures remains incomplete. Here, we report the chemical structures of the capsular polysaccharides of serotypes 39, 42, and 47F from the genetic cluster 4, and discuss the structures in the context of structures from serologically and genetically related serotypes. Antigenic determinants can be approximated in this manner. The structure of the serotype 39 capsular polysaccharide is [formula: see text] and has identical composition to the capsular polysaccharide 10A, but two different linkages. The serotype 42 structure [formula: see text] closely resembles the genetically related serotype 35A, which does not contain residue A. The structure of the serotype 47F capsular polysaccharide [formula: see text] is somewhat different from a recently determined structure from the same serogroup, while containing a structural motif that is reflected in serotype 35A and 42 capsular polysaccharide structures, thus explaining the cross-reactivity of serotype 47F with the typing serum 35a.