Mannan cell-wall

Many different types of carbohydrate-containing molecules are located on the surface of microbial cells. Some of these are components of die microbial cell wall and are limited to certain types of micro-organisms such as bacterial peptidoglycan, lipopolysaccharides, techoic adds and yeast mannans. Other polysaccharides are not... 

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. 

Biosorption is a rather complex process affected by several factors that include different binding mechanisms (Figure 10.4). Most of the functional groups responsible for metal binding are found in cell walls and include carboxyl, hydroxyl, sulfate, sulfhydryl, phosphate, amino, amide, imine, and imidazol moieties.4 90 The cell wall of plant biomass has proteins, lipids, carbohydrate polymers (cellulose, xylane, mannan, etc.), and inorganic ions of Ca(II), Mg(II), and so on. The carboxylic and phosphate groups in the cell wall are the main acidic functional groups that affect directly the adsorption capacity of the biomass.101... 

Codium cell-walls contain no crystalline mannan unless they are treated with boiling water. An orthorhombic unit-cell with a = 7.21 A (721 pm), b(fiber axis) = 10.27 A (1.027 nm), and c = 8.82 A (882 pm) was derived. Cell-wall material treated with 12-14% potassium hydroxide gave a different diagram, corresponding to mannan II. In a water-saturated atmosphere, the unit cell for mannan II is monoclinic, with a = 18.8 A (1.88 nm), fo(fiber axis) = 10.2 A (1.02 nm), c = 18.7 A (1.87 nm), and R = 57.5°. 

Fungus A general term to denote a group of eukaryotic protist, including mushrooms, yeasts, rusts, molds, smuts, etc., which are characterized by the absence of a rigid cell wall composed of chitin, mannans, and sometimes cellulose. 

The majority of ascomycetous yeasts form cell-wall mannans or ga-lactomannans having main chains of (1— 6)-linked a-D-mannopyrano-syl residues, often substituted at 0-2 by a-linked glycosyl groups. The linkage types in the rest of the side chains vary widely, and can consist of 2-O-substituted a- or /3-D-mannopyranosyl residues, or 3-O-substi-... 

A fluorescent tag (fluorescein isothiocyanate) attached to the lectin Concanavalin A is useful in staining yeast cell wall fragments (Siebert et al., 1981). Concanavalin A specifically binds to mannan, which is prominent in yeast cell walls. 

Galactans, mannans (hemicelluloses, cell-wall storage)... 

Fig. 2.—Diagram of Hypothetical Structure of Yeast Cell-wall JPhosphoric diester links are represented by —P— (E) is 0-D-fructofuranosidase is D-glucan is D-mannan and S is sulfur. From Ref. 117 printed here by permission of Cambridge University Press.]...

The cell wall of the yeast Saccharomyces is rich in mannoproteins that contain 50-90% mannose.264 The 250-residue mannan chains consist of an a-1,6-linked backbone with mono-, di-, and tri-mannosyl branches. These are attached to the same core structure as that of mammalian oligosaccharides. All of the core structures are formed in a similar way.258 265 The mannoproteins may serve as a "filler" to occupy spaces in a cell wall constructed from P-1,3- and P-l,6-linked gly-cans and chitin. All of the four components, including the mannoproteins, are covalently linked together.266 As was emphasized in Chapter 4 (pp. 186-188)... 

The structures of the cell-wall D-mannans of several other yeasts have been investigated381 by use of this exo-a-D-mannanase. Five were degraded to the (l->6)-a-D-mannan chain. Those which contained jB-linked d-mannosyl units or a-D-galactosyl groups in the side chains were not significantly hydrolyzed. However, removal, by partial hydrolysis with acid, of the a-D-galactosyl units from five galactomannans, and of /3-linked D-mannosyl units from three other D-mannans, rendered these polysaccharides partially susceptible to hydrolysis by exo-a-D-mannanase, consistent with an a-linked-D-mannan structure. 

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