Acceptive Immunity: The Role of Fucosylated Glycans in Human Host–Microbiome Interactions

The growth in the number of chronic non-communicable diseases in the second half of the past century and in the first two decades of the new century is largely due to the disruption of the relationship between the human body and its symbiotic microbiota, and not pathogens. The interaction of the human immune system with symbionts is not accompanied by inflammation, but is a physiological norm. This is achieved via microbiota control by the immune system through a complex balance of pro-inflammatory and suppressive responses, and only a disturbance of this balance can trigger pathophysiological mechanisms. This review discusses the establishment of homeostatic relationships during immune system development and intestinal bacterial colonization through the interaction of milk glycans, mucins, and secretory immunoglobulins. In particular, the role of fucose and fucosylated glycans in the mechanism of interactions between host epithelial and immune cells is discussed.     

富含岩藻糖苹果皮果胶的提取与理化性质

以超声辅助柠檬酸提取法从苹果皮中提取苹果果胶,并对所提取苹果皮果胶进行理化性质测定和分析。在最佳提取条件下（pH 2.5柠檬酸,450 W超声30 min）,苹果皮果胶得率为14.6%。理化性质分析表明：所得苹果皮果胶的酯化度为69.9%、糖醛酸含量为58.5%、总糖含量为92.8%,分子质量大于400 kD。气相色谱法分析表明：该方法提取的苹果皮果胶由鼠李糖、岩藻糖、阿拉伯糖、木糖、葡萄糖、半乳糖、葡萄糖醛酸及半乳糖醛酸8 种单糖组成,单糖组成的物质的量比为9.5∶19.2∶4.6∶0.1∶4.6∶3.6∶2.3∶56.3,岩藻糖含量高达19.2%。而超声法、盐酸法提取的苹果皮果胶中未检测到岩藻糖。进一步研究表明：富含岩藻糖的苹果皮果胶的提取与柠檬酸作萃取剂有一定关系。     

Synthesis of GDP‐Fucose on a Soluble Support: A Donor Substrate for the Fucosyltransferases

The synthesis of GDP‐fucose on a poly(ethylene glycol)‐based soluble support is described. Our strategy relies on the attachment of the 6‐deoxy‐6‐thio‐L ‐galactose onto the polymer via a thioether linkage , and its conversion to GDP‐fucose using established methods. We thus obtained GDP‐fucose bound to the polymer that was tested as an acceptor for the recombinant fucosyltranferase FucT‐III.     

1,6-α-L-Fucosidases from Bifidobacterium longum subsp. infantis ATCC 15697 Involved in the Degradation of Core-fucosylated N -Glycan

Bifidobacterium longum subsp. infantis ATCC 15697 possesses five α-L-fucosidases, which have been previously characterized toward fucosylated human milk oligosaccharides containing α1,2/3/4-linked fucose [Sela et al.: Appl. Environ. Microbiol., 78, 795-803 (2012)]. In this study, two glycoside hydrolase family 29 α-L-fucosidases out of five (Blon_0426 and Blon_0248) were found to be 1,6-α-L-fucosidases acting on core α1,6-fucose on the N-glycan of glycoproteins. These enzymes readily hydrolyzed p-nitrophenyl-α-L-fucoside and Fucα1-6GlcNAc, but hardly hydrolyzed Fucα1-6(GlcNAcβ1-4)GlcNAc, suggesting that they de-fucosylate Fucα1-6GlcNAcβ1-Asn-peptides/proteins generated by the action of endo-β- N-acetylglucosaminidase. We demonstrated that Blon_0426 can de-fucosylate Fucα1-6GlcNAc-IgG prepared from Rituximab using Endo-CoM from Cordyceps militaris. To generate homogenous non-fucosylated N-glycan-containing IgG with high antibody-dependent cellular cytotoxicity (ADCC) activity, the resulting GlcNAc-IgG has a potential to be a good acceptor substrate for the glycosynthase mutant of Endo-M from Mucor hiemalis. Collectively, our results strongly suggest that Blon_0426 and Blon_0248 are useful for glycoprotein glycan remodeling.     

丙酸杆菌代谢物益生因子的研究

丙酸杆菌在发酵过程中产生多种代谢产物．添加到食品中能够对人体起到营养保健作用。本文主要介绍丙酸杆菌的发酵产物中已被证实的具有益生作用的因子。     

Multiple forms of polygalacturonase from mango (Mangifera indica L. cv Alphonso) fruit

Polygalacturonase (PG) from mango pulp revealed three isoforms (I, II, III) upon ion exchange and gel filtration chromatography, each having an abundance of 68%, 6% and 26%, and molecular weights (M_r) 40, 51 and 45 kDa, respectively. The pH optimum for the isoforms was between 3 and 4. PG-I was stable over a wide pH range (4–7.5) unlike PG II and III, which were stable at pH 4 and 5, respectively. The optimum temperature was around 40 °C for all the three isoforms. Their apparent K_m for pectic acid was in the range 0.22–0.25 mg ml⁻¹. The V_max for PG I, II and III was 5.7, 3.6 and 4.4 μmol GalA equivalent h⁻¹, respectively. Cd²⁺, Cu²⁺ and Fe²⁺ and EDTA inhibited whereas GalA, Gal, Fuc, Rha and Ara stimulated PG-I activity, in particular. The major endogenous substrates for mango PG were identified to be two rhamnogalacturonans varying in their sugar ratio. These results are discussed in the light of pectin dissolution in vivo in ripening mango.     

Fucose Ameliorates Tritrichomonas sp.-Associated Illness in Antibiotic-Treated Muc2−/− Mice

The mucus layer in the intestine plays a critical role in regulation of host–microbe interactions and maintaining homeostasis. Disruptions of the mucus layer due to genetic, environmental, or immune factors may lead to inflammatory bowel diseases (IBD). IBD frequently are accompanied with infections, and therefore are treated with antibiotics. Hence, it is important to evaluate risks of antibiotic treatment in individuals with vulnerable gut barrier and chronic inflammation. Mice with a knockout of the Muc2 gene, encoding the main glycoprotein component of the mucus, demonstrate a close contact of the microbes with the gut epithelium which leads to chronic inflammation resembling IBD. Here we demonstrate that the Muc2^−/− mice harboring a gut protozoan infection Tritrichomonas sp. are susceptible to an antibiotic-induced depletion of the bacterial microbiota. Suppression of the protozoan infection with efficient metronidazole dosage or L-fucose administration resulted in amelioration of an illness observed in antibiotic-treated Muc2^−/− mice. Fucose is a monosaccharide presented abundantly in gut glycoproteins, including Mucin2, and is known to be involved in host–microbe interactions, in particular in microbe adhesion. We suppose that further investigation of the role of fucose in protozoan adhesion to host cells may be of great value.     

Preparation of epigallocatechin gallate-loaded nanoparticles and characterization of their inhibitory effects on Helicobacter pylori growth in vitro and in vivo

A variety of approaches have been proposed for overcoming the unpleasant side effects associated with antibiotics treatment of Helicobacter pylori (H. pylori) infections. Research has shown that epigallocatechin-3-gallate (EGCG), a major ingredient in green tea, has antibacterial activity for antiurease activity against H. pylori. Oral EGCG is not good because of its digestive instability and the fact that it often cannot reach the targeted site of antibacterial activity. To localize EGCG to H. pylori infection site, this study developed a fucose–chitosan/gelatin nanoparticle to encapsulate EGCG at the target and make direct contact with the region of microorganisms on the gastric epithelium. Analysis of a simulated gastrointestinal medium indicated that the proposed in vitro nanocarrier system effectively controls the release of EGCG, which interacts directly with the intercellular space at the site of H. pylori infection. Meanwhile, results of in vivo clearance assays indicated that our prepared fucose–chitosan/gelatin/EGCG nanoparticles had a significantly greater H. pylori clearance effect and more effectively reduced H. pylori-associated gastric inflammation in the gastric-infected mouse model than the EGCG solution alone.     

Chemoenzymatic Synthesis of GDP‐L‐Fucose Derivatives as Potent and Selective α‐1,3‐Fucosyltransferase Inhibitors

Fucosyltransferases (FucTs) usually catalyze the final step of glycosylation and are critical to many biological processes. High levels of specific FucT activities are often associated with various cancers. Here we report the development of a chemoenzymatic method for synthesizing a library of guanosine diphosphate β‐L ‐fucose (GDP‐Fuc) derivatives, followed by in situ screening for inhibitory activity against bacterial and human α‐1,3‐FucTs. Several compounds incorporating appropriate hydrophobic moieties were identified from the initial screening. These were individually synthesized, purified and characterized in detail for their inhibition kinetics. Compound 5 had a K_i of 29 nM for human FucT‐VI, and is 269 and 11 times more selective than for Helicobacter pylori FucT (K_i=7.8 μM) and for human FucT‐V (K_i=0.31 μM).