Saccharides lipopolysaccharide

A structural study on lipid A and the O-specific polysaccharide of the lipopoly-saccharide from a clinical isolate of Bacteroides vulgatus from a patient with Crohn s disease was conducted by Hashimoto and coworkers [39]. They separated two potent virulence factors, capsular polysaccharide (CPS) and lipopolysaccharide (LPS), from a clinical isolate of B. vulgatus and characterized the structure of CPS. Next, they elucidated the strucmres of O-antigen polysaccharide (OPS) and lipid A in the LPS. LPS was subjected to weak acid hydrolysis to produce the lipid A fraction and polysaccharide fraction. Lipid A was isolated by PLC, and its structure was determined by MS and NMR. 

This enzyme [EC 2.4.1.56] catalyzes the reaction of UDP-A-acetyl-D-glucosamine with a lipopolysaccharide to produce UDP and an A-acetyl-D-glucosaminyl-lipopoly-saccharide. Thus, this enzyme transfers A-acetylgluco-saminyl residues to a D-galactose residue in the partially completed lipopolysaccharide core. 

The occurrence of 3-deoxy-D-manno-octulosonic acid in lipopoly-saccharides has prompted its synthesis,537 together with the D-gal-octo158 and the D-gluco analogs.157 Although gas-liquid chromatography was successfully used to analyze the products of these syntheses, it has been reported that methanolysis of a bacterial endotoxin lipopolysaccharide failed to yield 3-deoxy-D-manno-octulosonic acid, presumably because of the lability of the latter to acid.381 However, Kasai and Nowotny have reported four peaks for the O-trimethylsilyl derivatives of 3-deoxy-D-manno-octulosonic acid obtained by methanolysis of the glycolipid from a Salmonella minnesota mutant.538 Reduced 3-deoxy-D-manno-octulosonic acid and its methyl ester have also been analyzed successfully as their acetates.339,539... 

Sterol carrier protein 2 has also been shown to be involved in the intracellular transport and metabolism of cholesterol. Hirai et al. (1994) suggested that sterol carrier protein 2 plays an important role during foam cell formation induced by acetylated LDL and may be an important step in atherosclerosis [142], Lipoproteins can bind lipopolysaccharide and decrease the lipopoly-saccharide-stimulated production of proinflammatory cytokines [142, 143], In addition, lipoprotein entrapment by the extracellular matrix can lead to the progressive oxidation of LDL because of the action of lipoxygenases, reactive oxygen species, peroxynitrite, or myeloperoxidase [144, 145],... 

Like Escherichia coli, clinical isolates of H. pylori produce high-molecular-mass (smooth-form) lipopolysaccharide (LPS) composed of an outermost saccharide moiety, divided into the O-polysaccharide or O-specific chain (O-antigen) and core oligosaccharide (OS) regions, covalently linked to lipid A (Fig. 10.1). H. pylori smooth-form LPS possesses O-polysaccharide chains of relatively constant chain length compared with those of enterobacterial LPS (Moran et al., 1992a Moran, 1999). Their length is determined by an enzymatic molecular ruler mechanism... 

Lipids can also be combined with saccharides to form hpopolysac-charides (lipids covalently linked to small saccharides). Although httle work has been done on the geochemistry of lipopolysaccharides, they... 

Bacteria are simple unicellular organisms that constantly grow. They have a membrane and cell wall. Fimbriae are especially important for bacterial adhesion, a critical factor in dental disease development. Lipopolysaccharide is a covalent lipid and polysaccharide structure that contains unusual saccharides and fatty acids. The lipid is at one end and inserts it into the plasma membrane. LPS is invariably recognized as foreign by receptors on mammalian cells that recognize the unique structure and activate inflammation such as gingivitis. 

Recent studies have shown that pathogens share molecular patterns that activate the innate immune response and influence the later adaptive reaction. For example, many Gram-negative bacteria express lipopolysaccharides on their outer membranes. Lipopoly-saccharides interact with Toll-like receptors (TLR) on dendritic cells, macrophages, and neutrophils to induce production of TNF-a and other cytokines. 

Salmonella typhimurium - This organism s O antigen is the major lipopolysaccharide component of the outer membrane. Lipopoly saccharides contain repeating oligosaccharide units attached to a basal core... 

Dong, Z., Qi, X., Xie, K., and Fidler, I. J. (1993). Protein tyrosine kinase inhibitors decrease induction of nitric oxide synthase activity in lipopolysaccharide-responsive and lipopoly-saccharide-nonresponsive murine macrophages. /. Immunol. 151, 2717-2724. 

The polysaccharide moiety of the lipopolysaccharide of Schizothrix calcicola contains 2-amino-2-deoxy-D-glucose, D-galactose, D-glucose, D-mannose, D-xylose, and L-rhamnose. In contrast to many enterobacterial lipopoly-saccharides, the major fatty acid component has been identified as 3-hydroxy-palmitic acid and not 3-hydroxymyristic acid. 

There are three major stages in O-antigen assembly, which are the construction of the repeating unit, the formation of the polymer chain and its attachment to the core region of the lipopolysaccharide. Undecaprenyl pyrophosphoryl saccharides are involved in all of these, again forming an isoprenyl phosphate cycle. 

In Gram-negative organisms the entry of lipopolysaccharide into the outer membrane occurs by transport through connections to the cytoplasmic membrane the mechanism of this is unknown. No alteration of saccharide is possible once the polymer has left the cytoplasmic membrane, but its cross-linking to other molecules of lipopolysaccharide must occur after it has migrated. 

Several Gram-negative bacteria express smooth lipopolysaccharide (LPS) which consists of repeating saccharide units beyond the core saccharide each repeat is called an O-unit that usually comprises two to six sugars and the entire structure made up of repeating units is called the 0-antigen. In addition, several of these pathogens express capsular polysaccharide which also plays a key role in virulence. 

Endotoxin is a term often used synonymously with lipopolysaccharide (LPS), a major component of the Gram-negative bacterial cell wall. Endotoxin has been estimated to make up between 3 and 4% of the dry weight of Escherichia coli K12. The LPS molecule consists of a Lipid A component anchored in the outer membrane. This is attached to a series of saccharide units specific for different strains of Gram-negative bacteria. LPS is extremely heat stable and needs to be heated to 180 °C for three hours to ensure inactivation. When injected into the bloodstream, it activates the alternative complement pathway and produces a pyrogenic reaction. Studies on laboratory animals have shown that it can produce severe reactions when inhaled in microgram quantities. ... 

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