A-Mannan

Several methylated sugars have been identified in hydrolyzates of LPS, cell-wall polysaccharides, and extracellular polysaccharides. A considerable number of these have been found in the LPS from photosynthetic prokaryotes. Two polysaccharides from Mycobacterium species, a glucan" and a mannan" are remarkable in that they contain high percentages of methylated sugars. Glycolipids from Mycobacterium species are also rich in methylated sugars, some of which have not been found elsewhere, but this is beyond the scope of the present article. 

Kozutsumi, Y, Kawasaki, T, and Yamashima, I (1980) Isolation and characterization of a mannan-binding protein from rabbit serum Biochem Biophys Res Commun 95, 658—664. 

Out of 364 other tested enterobacteria 3 E. coli strains were positive, as were 8 of 9 Candida yeast isolates. These findings are not surprising because reciprocal cross-reactions between Salmonella Cl and some E. coli strains are well known (26) and in yeasts a mannan consisting of an a,l- -6 linked poly-D-mannose backbone with branches of a,l->-2 and a,l- -3 linked D-mannose residues is a principal cell-wall constituent (27). 

The fine structure of mycobacterial LAM with a range of structural diversity is generally well understood (Fig. 14.8) [257, 258], The core structure of LAM is composed of a phosphatidylinositol moiety connected to a mannan domain consisting of u( 1 - 6)- and a(l - 2)-linked mannopyranose residues. The mannan domain is linked to arabinan composed of (1 —>-5)-, a(l- 3)-, and p(l- 2)-linked arabinofuranose... 

Serologically active galactomannans, purified by way of their insoluble Fehling complexes, were obtained from mycelial and yeastlike forms of Paracoccidioides brasiliensis and Blastomyces dermaditidis, and shown by methylation analysis to consist of galactofuranosyl and mannopyranosyl units attached to a mannan core.142... 

The interaction between con A and a-mannans from a variety of micro-organisms was studied by So and Goldstein.204 The mannans from Saccharomyces cerevisiae, Saccharomyces rouxii, and Sarcina sp., and the phosphomannan from Saccharomyces pini Y-2579, all gave classical precipitin curves similar to those obtained for dextrans,320,362 but unlike the extended curves given by glycogen.369 A synthetic, linear (1—>3)-a-D-mannopyranan did not precipitate204 with con A. 

The greater reactivity of a-mannans compared to other con A-reactive polysaccharides was indicated by several observations (1) the con A-... 

It was formerly believed that coniferous woods contain a mannan. However, before the polysaccharide containing the mannose residues was isolated in a state of purity, Leech d and Anthis> were able to show that it was a glucomannan, by the isolation of disaccharides containing both glucose and mannose from a hydrolysate of polysaccharide material enriched in the mannose-containing material. This observation was later confirmed by the isolation of pure glucomannans from these woods. - ... 

The aqueous extract of whole, brewers yeast cells contained a mannan, termed cerebrosan, which was monodisperse on ultra-centrifugation. It had a specific rotation of -1-84° and contained 1.2% of nitrogen. The molecular weight was 3.4 X 10 , calculated from a value of S209.75 X 10 and the known relative specific volume. 

The structure of the mannan, or mannans, in wood cannot be described with certainty. Hess and Liidtke isolated a mannan from pine sulfite pulp identical with ivory-nut mannan-A in optical rotation and x-ray diagram. Husemann prepared, from spruce hemicellulose, fractions having rotational values in agreement with those for the mannan from pine sulfite... 

Evidence for a chemical linkage between cellulose and mannan, at least in softwood pulps, continues to accumulate. In this connection, Steinmann and coworkers have observed that, during the normal preparation of cellulose acetate, a considerable part of the xylan may be lost (30 to 60%), whereas the mannan content is not greatly affected. These authors suggest that this may indicate that the mannan is bound to the anhydroglucose chain. According to these workers, certain differences in properties of cellulose acetate prepared from different samples of cellulose can be explained if a mannan-to-cellulose bond actually does exist. However, it must be realized that no definitive proof has been presented of a mannan-to-cellulose linkage in any preparation of wood cellulose. 

Using Py-FI MS, even better results were obtained [3] for the differentiation of the type of bonds. Using oven pyrolysis at 500° C and evaporation of the sample in the MS source, different spectra were generated from 1,3-a-mannan, 1,3-p-mannan, 1,4-p-mannan, 1,2-a-mannan [3], and are shown in Figures 7.1.11 (A) to 7.1.11 (D). 

Ito and coworkers assembled a series of a-mannans working under frozen solvent conditions, and observed striking rate accelerations when compared to the same reactions in fluid media.5 For example, the trisaccharide thioglycoside 14 was coupled to the hexasaccharide 13 at 4 °C with activation by methyl triflate to give the nonasaccharide15 (Scheme 4). When toluene was employed as solvent, after 22 h at 4 °C only 6% of the product was obtained, whereas in frozen xylene under the same... 

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