Polysaccharides arabinogalactan

The cell walls of mycobacteria contain three structures peptidoglycan, an arabinogalactan polysaccharide and long chain hydroxy fatty acids (mycolic acids) which are all covalently linked. Additional non-covalently attached lipid components found in the wall include glycolipids, various phospholipids and waxes. The lipid-rich nature of the mycobacterial wall is responsible for the characteristic acid-fastness on staining and serves as a penetration barrier to many antibiotics. Isoniazid and ethambutol have long been known as specific antimycobacterial agents but their mechanisms of action have only recently become more clearly understood. 

Properties of the metal particles under study depends on the synthesis conditions such as availability of stabilizing medium, its composition, the type of reducer and temperature. Nanosized metal particles possess lyophobic properties. We have established a possibility to use the arabinogalactan polysaccharide for their stabilization in the aqueous medium. It efficiently reduces and stabilizes nanoparticles of silver and other noble metals. 11 is expected also that the stabilizer controls the electronic characteristics of metal nanoparticles. Our results below have confirmed this assumption. 

Ethambutol is thought to block assembly of the arabinogalactan polysaccharide by inhibition of an arabinotransferase enzyme. Cells treated with ethambutol accumulate the isoprenoid intermediate decaprenylarabinose, which supplies arabinose units for assembly in the arabinogalactan polymer. 

Considering the Gal/" part of the arabinogalactan polysaccharide produced by M tuberculosis (Fig. 3), the biosynthesis begin with connection of a N-acetyl-a-u-glucosamine-l-phosphate (a-o-GlcNAcp-l-P) residue to a decaprenyl phosphate chain, anchored into the biological... 

Antonova G F, Maierle S N 1974 Characteristics of the composition of arabinogalactan polysaccharide produced in Siberian larchwood. Probl Fiziol Biokhim Drev Rast 1 4-5... 

Fruits and Cellulose, xyloglucans, arabinogalactans. Polysaccharides fiber... 

The common hemiceUulose components of arborescent plants are listed in Table 3. Xylans, arabinogalactans, and pectic substances are common to all while only traces (if at all) of glucomaimans are found in the cell walls of bamboo. Other polysaccharides are found in trace amounts in wood as well as in bark, growing tissues, and other specialized parts of trees. 

Within the scope of this review, the contributions of the last decade concerning cell-wall polysaccharides isolated from woody and other plant tissues will be reviewed according to the above-proposed classification of hemicelluloses including larch arabinogalactans. The present review article updates and extends previous reviews [3-5] and will focus in particular on new investigated plant sources, isolation methods, structural features, physicochemical and various functional properties of hemicelluloses. Attention will also be paid to the modification of isolated hemicelluloses or hemicellulosic materials and the appHcation possibiUties of hemicelluloses and their derivatives, including their use for the production of composite materials and other biomaterials. 

Arabinogalactans (AGs) are widely spread throughout the plant kingdom. Many edible and inedible plants are rich sources of these polysaccharides. AGs occur in two structurally different forms described as type I and type II, associated with the pectin cell-wall component by physical bonds and some of them are covalently linked to the complex pectin molecule as neutral side chains. Commercial pectins always contain AG 10-15%). AG of type I has a linear (1 4)-y0-o-Galp backbone, bearing 20-40% of of-L-Ara/ residues (1 5)-linked in short chains, in general at position 3. It is commonly found in pectins from citrus, apple and potato [6]. Recently, this AG type has been isolated from the skin of Opuntia ficus indica pear fruits [372]. 

The arabinogalactans have more frequently been reported for activity in various biological systems. Arabinogalactans are often classified in three groups arabino-4-galactans (Type 1), arabino-3,6-galactans (Type II) and polysaccharides with arabinogalactan side chains (Type III) [14]. The latter type are also called the real pectins [10,11]. Only types I and II will be dealt with in this chapter, as Type III are equal to the pectins discussed below. 

Polysaccharides isolated from the seeds of C. chinensis have effects both as immunostimulants and as antioxidants. The polysaccharide CS-A-3-/1 has a backbone of a-D-l,4-hnked GalpA and /1-L-1,2-Rhap imits with branches at C-4 of the Rhap residues and at C-3 of GalpA residues that are composed of an arabinogalactan and glucobiose. The Ara/ imits are terminal and 1,5-... 

Black pepper contains several polysaccharides of which one shows a strong effect as an immune enhancer based on the fact that the polymer is an anti-complementary polysaccharide. The polysaccharide has an Mw of approx. 40 kD. It is composed basically of rhamnose, arabinose, galactose and galac-turonic acid, and shows a high binding capacity for the Yariv reagent. This indicates that the side chain of the polymer is of the arabinogalactan type II, which is a common structure for several polysaccharides with an effect on the complement system [70]. 

KELLY G s (1999) Larch arabinogalactan Clinical relevance of a novel immune-enhancing polysaccharide. Med Rev, 4(2) 96-103. 

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