Oligosaccharides lipopolysaccharide

The Gram-negative cell envelope (Fig. 1.4) is even more complicated essentially, it contains lipoprotein molecules attached covalently to the oligosaccharide backbone and in addition, on its outer side, a layer of lipopolysaccharide (LPS) and protein attached by hydrophobic interactions and divalent metal cations, Ca and Mg. On the inner side is a layer of phospholipid (PL). 

In Gram-negative bacteria the cell wall is only about 3 nm thick, and located in the extended periplasmatic space between the inner membrane (IM) and an additional outer membrane (OM). The lipid monolayer in the outer leaflet of the OM contains about 90% lipopolysaccharides (LPS). LPS consist of Lipid A and an oligosaccharide component, which is highly specific for individual bacterial species and phenotypes [108, 114]. 

Lipopolysaccharides Human pathogenic and marine bacteria Lipid A + various attached oligosaccharide decorations Oxidative burst, and oxylipin production in L. digitata Kupper et al. 2006... 

Jacques, M. (1996). Role of lipo-oligosaccharides and lipopolysaccharides in bacterial adherence. Trends Microbiol. 4, 408-409. 

N. catarrhalis,560 N. perflava,559 Moraxella duplex and Micrococcus calco-aceticus,443 and Escherichia coli,420 Vicari and Kabat,45 in studies of blood-group oligosaccharides, and Hellerqvist and colleagues,53 in an examination of the common core-polysaccharide of Salmonella typhimurium, have used similar methods. The examination of amino sugars as their peracetylated aminodeoxyalditols has also been used by Liideritz and colleagues72 to establish the occurrence of 4-amino-4-deoxy-L-arabinose in Salmonella lipopolysaccharides, and has been extended to aminodeoxyheptoses by Williams and Perry.561... 

Terminal 3,6-dideoxyhexoses that occur in lipopolysaccharides from Salmonella and Yersinia (Pasteurella) species7 could be hydrolyzed off with a high degree of selectivity. They may, therefore, be located by methylation analysis of the original lipopolysaccharide and of a partially hydrolyzed sample. Thus, for the Salmonella typhi-murium 395 MS lipopolysaccharide, composed18 of oligosaccharide... 

Structural studies on the oligosaccharide derivatives obtained by partial, acid hydrolysis of fully methylated polysaccharides often furnish valuable information on the positions at which the oligosaccharides were linked in the original polysaccharide. When the folly methylated Klebsiella O group 9 lipopolysaccharide,27 which contains D-galactopyranose and D-galactoforanose residues, was subjected to mild, acid hydrolysis, and the product reduced with lithium aluminum deuteride and remethylated with trideuteriomethyl iodide, a good yield of the disaccharide derivative 10 was obtained. 

FIGURE 7-32 Bacterial lipopolysaccharides. (a) Schematic diagram of the lipopolysaccharide of the outer membrane of Salmonella ty-phimurium. Kdo is 3-deoxy-o-manno-octulosonic acid, previously called ketodeoxyoctonic acid Hep is L-glycero-D-mannoheptose AbeOAc is abequose (a 3,6-dideoxyhexose) acetylated on one of its hydroxyls. There are six fatty acids in the lipid A portion of the molecule. Different bacterial species have subtly different lipopolysaccharide structures, but they have in common a lipid region (lipid A), a core oligosaccharide, and an "O-specific" chain, which is the prin-... 

Glycolipids and lipopolysaccharides are components of the plasma membrane with covalently attached oligosaccharide chains exposed on the cell s outer surface. 

In the polymers of groups (1) and (2), polysaccharide chains composed of oligosaccharide repeating-units (sometimes, partially modified) are usually linked to a unique oligosaccharide unit present near the point of attachment of the chain to another polymeric chain, or to a lipid anchor. This unit is called the linkage region in the polymers of bacterial cell-wall, and the core region in lipopolysaccharides. 

In bacterial lipopolysaccharides, O-specific chains composed of repeating, or modified repeating, units are linked to a unique oligosaccharide sequence of the core region which is connected to a lipid A fragment serving as a hydrophobic anchor embedded in the bacterial outer-membrane. Biosynthesis of O-specific chains was found to occur independently on formation of other structural fragments of the lipopolysaccharide molecule. Both block and monomeric mechanisms were demonstrated for the biosynthesis of these polymers. 

Figure 1 represents the general structure of Salmonella lipopolysaccharides. They contain an external polysaccharide, the O-antigenic chain, and an innermost component, termed lipid A. O-chain and lipid A are linked to each other by an oligosaccharide referred to as the core. O-Specific Chains. As indicated in Figure 1, O chains are in general made up of repeating units of di-, tri-, or higher oligosaccharides. In rare cases the O-chain is a homopolysaccharide. The structure of the O-chain is unique to each bacterial serotype great diversity is encountered in the structures of O-chains.

Tetra, octa, and dodecasaccharides have been prepared from Salmonella typhimurium lipopolysaccharide by specific degradation of the O chain with phage enzyme. These oligosaccharides contain 1,2, or 3 chemical repeating units (Svenson and Lindberg, 1981). 

N. K. Kochetkov, in L. Anderson and F. M. Unger (Eds.), Synthesis of O-antigenic polysaccharides. Pathways for the polymerization of oligosaccharide repeating units, Bacterial Lipopolysaccharides Structure, Synthesis and Biological Activities, ACS Symp. Ser., Vol. 231, Amer. Chem. Soc., New York, 1983, pp. 65-81. 

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