Cell walls glucomannans

Glucomannans (GM) and galactoglucomannans (GGM), common constituents of plant cell walls, are the major hemicellulosic components of the secondary cell walls of softwoods, whereas in the secondary cell walls of hardwoods they occur in minor amounts. They are suggested to be present together with xylan and fucogalactoxyloglucan in the primary cell walls of higher plants [192]. These polysaccharides were extensively studied in the 1960s [6,193]. 

Figure 3. Distribution of polysaccharides through the cell wall. C, cellulose M, galacto-glucomannan X, arabino-4-O-methylglucuronoxylan.

Cell walls of woods contain other subgroups of hemicelluloses, in particular those composed primarily of D-mannopyranosyl or D-galactopyranosyl units. Glucomannans [11078-31-2] comprise 3—5% of the wood of angiosperms and 3—12% of the wood of gymnosperms. Galactoglucomannans... 

The cell wall of fungi is a complex, multilayered structure formed by at least two major polysaccharides. These major polysaccharides have been used as a taxonomic criterion for fungi, as some of them contain chitin-glucans, and others, glucomannans.123... 

Cellulose is the main component of the cell-wall which forms the insoluble skeletal framework of all higher plants. This polymer is associated with other polysaccharides, chiefly xylan, pectin, glucomannan, and hemicelluloses. 

Glucomannan, on the other hand, is biosynthesized from GDP-o-mannose and GDP-o-glucose. It is important to note that the activities of hemicellulose synthetases are controlled depending on the stage of cell wall formation. 

The predominant hemicelluloses in secondary cell walls of both monocotyledons and dicotyledons are xylans. These polysaccharides have a xylan main chain that is decorated with 4-0-methyl-D-glucopyranosyluronic acid, D-glucopyranosyluronic acid, L-arabinofuranosyl, and/or L-arabinopyranosyl units. These related polysaccharides are usually acetylated to various degrees. Gymnosperms contain glucomannans, also acetylated, as the principal secondary cell-wall hemicellulose [26]. 

In addition to chitin (O Sect. 2.2), yeast cell walls may contain a (1 3)- -glucan, a (1 6)- -glucan, various mannans, or a galactan. Other cell-wall components of certain fungi are rhamnomannans, glucomannans, galactomannans, xylomannans, glucuronoxylomannans, and other polysaccharides [42]. 

In contrast to the cell walls of parenchymatous tissues of dicotyledons, those of cereal grains (wheat, barley, etc.) contain very little, or no, pectic substances. The primary walls of most cereal grains have cellulose microfibrils, which are closely associated with glucomannan, and these fibrillar structures are embedded in an amorphous matrix of hemicelluloses, which consists mainly of arabinoxylans and/or P-D-glucans, some of which are cross-linked by phenolic esters and/or proteins (Selvendran,... 

A number of plant [106, 178-183] and algal [64, 176] polysaccharides have structures based on a P(l-4)mannan main chain - P(l-4)mannan, a(l-6)galacto-P(l-4)-D-mannan and the related P(l-4)-D-glucomannan and galacto-P(l-4)glucomannan. They serve as cell wall structural material and as carbohydrate reserve polymers. An unbranched P(l-2) mannan of low molecular weight has been reported from the insect flagellate Herpetomonas samuelpessoai [184]. 

Mannan from thickened cell walls of palm seeds yeast is d-Manp in 3-l- 4 and side chain at 3-l->6. Glucomannan from tuber consists of Glc and Man. Man is a constituent of oligosaccharides of iV-glycoproteins in a-1—>2, al 3 and al—>6 (as branching points) and 31—>4 (main) linkages. Man is attached to serine in 0-glycoproteins. 

Lechat, H., Amat, M., Mazoyer, J., Buleon, A., and Lahaye, M. (2000). Structure and distribution of glucomannan and sulfated glucan in the cell walls of the red alga Kctppctphycus alvarezii (Gigartinales, Rhodophyta).. Phycol. 5,891-902. 

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