2-Octulosonic acid structure

Circles represent polar head groups of phospholipids. MDO, membrane-derived oligosaccharides KDO, 3-deoxy-manno-octulosonic acid (structures for KDO and heptose are in Fig. 4-15). From Raetz and Dowhan.587... 

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-... 

In vivo, pyruvate lyases perform a catabolic function. The synthetically most interesting types are those involved in the degradation of sialic acids or the structurally related octulosonic acid KDO, which are higher sugars typically found in mammalian or bacterial glycoconjugates [62-64], respectively. Also, hexose or pentose catabolism may proceed via pyruvate cleavage from intermediate 2-keto-3-deoxy derivatives which result from dehydration of the corresponding aldonic acids. Since these aldol additions are freely reversible, the often unfavourable equilibrium constants require that reactions in the direction of synthesis have to be driven by an excess of one of the components, preferably pyruvate for economic reasons, in order to achieve a satisfactory conversion. 

B. L. Reuhs, R. W. Carlson, and J. S. Kim, Rhizobium fredii and Rhizobium meliloti produce 3-deoxy-D-marmo-2-octulosonic acid-containing polysaccharides that are structurally analogous to group II K antigens (capsular polysaccharides) found in Escherichia coli, J. Bacteriol., 175 (1993) 3570-3580. 

The structure of the core ohgosaccharides of Campylobacter jejuni 02 LPS was found to contain 3-deoxy-D-m nno-octulosonic acid (Kdo), L-glycero-D-manno-heptose (LD-Hep), D-Gal, D-Glc and phosphoethanolamine based on H, and P NMR. Molecular mimicry in C. jejuni LPS has been implicated in the pathogenesis of Guillain-Barre syndrome by inducing antibodies to human gangliosides. 

Figure 2 Schematic representation of the LOS structure of N. meningitidis and N. gonor-rhoeae. Variations in the largest a chain are responsible for most of the immunogenic properties of the LOS. Abbreviations KDO, 3-deoxy-D-manno-2-octulosonic acid Hep, l -glycero-D-wanno-heptose Glc, glucose GlcNAc, A-acetylglucosamine PEA, phosphoethanolamine. Note Cii indicates an additional 11 carbon atoms, not the total chain length.

ABSTRACT This article describes recent developments in the chemistry of an important family of complex monosaccharides which have diverse structures and participate in a wide range of biological processes. For example 3-deoxy-D-/n nno-2-octulosonic acid (KDO) is a key component of the lipopolysaccharides (LPS) of Grammnegative bacteria, 3-deoxy-D-araftmo-2-heptulosonic acid (DAH) is a key intermediate in the biosynthesis of aromatic amino acids in bacteria and plants. A number of their syntheses that were achieved by homologation reactions of the natural carbohydrate units using enzymatic or chemical methods, as well as by total synthetic approaches are here included. Special emphasis is placed on new methodologies and their correlation with the biosynthetic pathway of the corresponding ulosonic acids. 

The structure of the K-13 antigenic polysaccharide of Escherichia coli consists of a repeating sequence of 3-linked D-ribofuranosyl residues and 7-linked 3-deoxy-D-man 20-octulosonic acid (KDO) residues, approximately 50% of which are O-acetylated at C-4 or C-5 The serological specificity of this polysaccharide is expressed through KDO and its 0-acetylated derivative. 

---