Polysaccharide phosphates

The hydroxyl groups of polysaccharides can be phosphorylated by reaction with tripolyphosphate at pH 5-6.5 the reaction is conducted at 110-130°C in the dry state and creates products containing 0.07-0.1% phosphorus [15] (reaction 7.14). Reaction of starch granules with tripolyphosphate at 150°C resulted in 0.3% covalently linked phosphorus that was distributed 9% at 0-3, 28% at 0-2, and 63% at 0-6 [19]. 

Granular starch has been cross-linked with phosphate by reaction of an aqueous alkaline suspension at pH 8-12 with 0.005-0.25% phosphorus oxychloride [15] (reaction 7.15). If starch granules are treated with 1% or higher concentrations of phosphorus oxychloride, the granules become very resistant to gela-tinization. Trimetaphosphate has also been used to produce phosphate cross-linkages [15] (reaction 7.16). Phosphorylation of 0-6 is predominant, and that of 0-3 is minimal [19]. 

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Polysaccharide-1-phosphates were extracted in some cases from bacterial cell walls. For example, TA isolated from Staphylococcus lactis 2102 consists of ca. 23 monomeric fragments each built of a-D-N-acetylglucosamine-1 -phosphate 22). These units are linked by the phosphoester bond at the 6 position in the sugar residue, as represented by 7. 

Nothing is known of the biosynthesis of most polysaccharide phosphates presumably ATP is the phosphate donor and it is likely that phosphate is added at, or just after, polysaccharide assembly, save where it forms a part of the molecular backbone. 

Phosphopolysaccharides (polysaccharide phosphate esters) of this kind occur frequently in living systems and in a number of important technological products. Many bacterial polysaccharides contain phosphate ester groups. In these the phosphate groups serve to link the saccharide rings to lipids or other biopolymer units as, for example, in the teichoic acids (Section 10.3). Phosphorylation is known to profoundly affect food properties (Chapter 12.4). 

S. Hunt, Polysaccharide phosphates, in Polysaccharide-Pmtein Complexes, Academie Press, 1970. 

Ion Exchange. Acidic polysaccharides containing uronic acids, sulfate, or phosphate groups are cation exchangers, binding metal ions. The... 

Another simple sugar that enters glycolysis at the same point as fructose is mannose, which occurs in many glycoproteins, glycolipids, and polysaccharides (Chapter 7). Mannose is also phosphorylated from ATP by hexokinase, and the mannose-6-phosphate thus produced is converted to fructose-6-phosphate by phosphomannoisomerase. 

In tandem with his studies of polysaccharides, Stacey had a research group investigating the chemistry of the unusual sugars found as components of carbohydrate macromolecules. In this context, derivatives of simple sugars, di- and trisaccharides, uronic acids, deoxy sugars, amino sugars, sugar sulfates, and phosphates were studied. 

The term polysaccharide has also been widely used for macromolecules containing glycose or alditol residues in which both glycosidic and phosphate diester linkages are present. 

Sodium carboxymethyl chitin and phosphoryl chitin had most evident influences on the crystallization of calcium phosphate from supersaturated solutions. They potently inhibited the growth of hydroxyapatite and retarded the rate of spontaneous calcium phosphate precipitation. These chitin derivatives were incorporated into the precipitate and influenced both the phase and morphology of the calcium phosphate formed (flaky precipitate resembling octacalcium phosphate instead of spherical clusters in the absence of polysaccharide) [175]. 

In a typical equilibrium dialysis study of charged polysaccharides an indicator ion, L (chromate), is included in the supporting electrolyte medium (phosphate buffer, pH 6.8, I 0.08) to allow assessment of the effective net charge of the polyanions via a modified form of Eq. 31, namely. 

Some sugar residues in bacterial polysaccharides are etherified with lactic acid. The biosynthesis of these involves C)-alkylation, by reaction with enol-pyruvate phosphate, to an enol ether (34) of pyruvic acid, followed by reduction to the (R) or (5) form of the lactic acid ether (35). The enol ether may also react in a different manner, giving a cyclic acetal (36) of pyruvic acid. 

In different polysaccharides of the teichoic acid type, monosaccharides or oligosaccharides are connected by phosphoric diester linkages. Two examples are the capsular antigens from Neisseria meningitides type A (56) and Haemophilus influenzae type c (57), respectively. Glycerol phosphate... 

There are solitary examples of other alditol phosphates as components of this class of polymers. Arabinitol 1-phosphate is part of the S. pneumoniae type 17F capsular polysaccharide. o-Glucitol 6-phosphate is a component of the group-specific polysaccharide from group B Streptococcus, which has a most unusual, ramified structure. In a polysaccharide from Nocardia... 

Acquired resistance to polymyxins in E. coli occurs because of chromosomal mutations which cause incorporation of aminoethanol and aminocarabinose in lipo-polysaccharide (LPS) in place of phosphate groups. The altered LPS has a decreased ionic charge which results in lowered binding of polymyxin and thus an increase in resistance to this group of antibiotics. 

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