Homoglycans

[Quincey Homer]

Thisdocument discusses various types of polysaccharides called homoglycans that are composed of a single type of monosaccharide unit. It focuses on starch, glycogen, cellulose, inulin, dextrans, and chitin. Starch is the storage carbohydrate in plants and is made of amylose and amylopectin. Glycogen serves the same function in animals, storing glucose in the liver and muscle. Cellulose provides structure to plants and is made of straight glucose chains. Inulin and dextrans are also homopolymers with different linkages between glucose units. Chitin contains N-acetylglucosamine units.Read less

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PECTOLYTIC and cellulolytic enzymes of phytopathogenic fungi are generally assumed to play an important part in the infection process in many plant diseases. There is an extensive literature covering this subject1. The enzymes facilitate the penetration of the fungus into the plant by a hydrolytic cleavage of polymers (pectic substances, cellulose) which constitute the plant cell walls. However, not only pectic substances and cellulose are building stones of the plant cell wall. In many cases arabans, galactans, or other homoglycans, heteroglycans and proteins are found as well2. Yet comparatively little work has been done concerning the role of enzymes hydrolysing these latter polymers. The main reason for this may be that these polymers are not all available commercially, and not that arabanases, galactanases, etc., should not be of possible importance in fungal invasion.

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Toll-like receptor (TLR) 4 is an important polysaccharide receptor; however, the relationships between the structures and biological activities of TLR4 and polysaccharides remain unknown. Many recent findings have revealed the primary structure of TLR4/MD-2-related polysaccharides, and several three-dimensional structure models of polysaccharide-binding proteins have been reported; and these models provide insights into the mechanisms through which polysaccharides interact with TLR4. In this review, we first discuss the origins of polysaccharides related to TLR4, including polysaccharides from higher plants, fungi, bacteria, algae, and animals. We then briefly describe the glucosidic bond types of TLR4-related heteroglycans and homoglycans and describe the typical molecular weights of TLR4-related polysaccharides. The primary structures and activity relationships of polysaccharides with TLR4/MD-2 are also discussed. Finally, based on the existing interaction models of LPS with TLR4/MD-2 and linear polysaccharides with proteins, we provide insights into the possible interaction models of polysaccharide ligands with TLR4/MD-2. To our knowledge, this review is the first to summarize the primary structures and activity relationships of TLR4-related polysaccharides and the possible mechanisms of interaction for TLR4 and TLR4-related polysaccharides.

All monosaccharide contain one or more chiral centers, and may be D or L enantiomers depending on the configuration about the chiral carbon most distant from the carbonyl. Glyceraldehyde, an aldotriose, contains one chiral carbon:

The arrangement of chiral carbons is unique for each monosaccharide. Molecules that differ in the configuration at only one of several chiral centers are epimers of each other. Glucose is an aldohexose with four chiral carbons and two epimers: galactose and manose:

Monosaccharide in aqueous solution exist as cyclic rings. The carbonyl carbon (C1) undergoes nucleophilic attack by the hydroxyl oxygen at the opposite end of the molecule. The carbonyl carbon is known as the numeric carbon and it symmetry results in two stereoisomers: alpha and beta.

Important derivatives of monosaccharide include sugars phosphates, deoxy sugars, and amino sugars. Sugar phosphates have a phosphate group substituting for a hydroxyl. In a deoxy sugar, an hydroxyl group has been deoxygenated. Amino sugars have an amino group instead of an hydroxyl.

Disaccharides contain two monosaccharide joined covalently by O-glycosidic bonds. Glycosidic bonds are formed by the anomeric carbon of a sugar condensing with the hydroxyl from another molecule

The naming of disaccharides specifies the linking atom: the molecule providing the numeric carbon ends in -syl. The name also contains the configuration of the glucosidic bond, for example alpha(1 to 4). Disaccharides also have common names, for example:

Polysaccharides can be homoglycans or heteroglycans. Homoglycans (homopolysaccharides) are polymers containing one type of monoshaccharide residue. Heteroglycans (heteropolysaccharides) are polymers of more than one type of monosaccharide residue. They are all created without a template by the addition of a particular monosaccharide or oligosaccharide residue. The length of a particular polysaccharide molecule varies within a population.

Carbohydrates are energy storage molecules with at least one carbonyl group. They are also found in protective and supportive structures as well as in some enzymes and nucleic acids. There are three major size classes: monosaccharide are simple sugars, oligosaccharides are chains of up to twenty monosaccharide, and polysaccharides are chains larger than twenty.

D-glucose is the main source of energy for many organisms and is stored intracellularly in polymeric form. The most common glucose storage homoglycans are starch and glycogen. Plants and fungi store glucose as starch, while animals store it as glycogen. Bacteria may store glucose as either starch or glycogen.

There are two forms of starch: amylose and amylopectin. Amylose is an unbranched polymer of 100 to 1000 D-glucose molecules attached to each other by alpha-1-to-4 bonds. Amylopectin is a branched version of amylose., were branches are attached by apha-1-to-6 glucosidic bonds to linear chains of residues linked by alpha-1-to-4 glucosidic bonds. Branches occur on average every 25 residues, with side chains containing about 15-25 glucose residues. Some chains are themselves branched. Amylopectin isolated from cells contains 300-600 glucose residues.

Glycogen is a branched polymer of glucose, with the same linkages as amylopectin but smaller branches occurring more frequently, about every 8-12 residues. Glycogen molecules are larger than starch molecules.

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The company notes that ChagaPure has demonstrated potent antibacterial antiviral and antifungal properties in clinical trials in Canadian and international laboratories. The extract has an antioxidant Oxygen Radical Absorbance Capacity (ORAC) value of more than 153,200 mol TE/100 g, according to analytical tests conducted by Brunswick Labs.

Bursting with bioactivity

ChagaPure is produced from wild mushrooms harvested from Northern British Columbia, Canada forests, containing some of the highest levels of immuno-stimulatory compounds available.

ChagaPure contains biologically active substances such as intensely colored water-soluble polyphenol pigments (chromogens) and complex phenolic aldehydes, phenols, oxi phenolic acids, quinines, endo-polysaccharides, hetero-polysaccharides, polysaccharides, beta-glucans, homoglycans, steroids, polyphenols, triterpenoids and antioxidants.ChagaPure has heightened antibacterial and antioxidant properties.

The company also notes that the extract is highly bioactive with a 20 to1 concentration ratio, meaning 20 kg of Chaga produces 1 kg of extract. It is standardized to contain a minimum of 56% polysaccharides with a chromogenic complex of over 51%.

Mushrooming innovation

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We all have heard about carbohydrates even when we were in the elementary school. It is one of the basic nutrients required for proper functioning of the body. It is mainly needed for energy in the body. Most carbohydrates in the body exist in the form of polysaccharides which is also called glycan. It is called polysaccharides because it is made up of many molecules of monosaccharide that is sugars.

There are some polysaccharides that contain just molecules of one sugar and they called homopolysaccharides or homoglycans. Typical example of homoglycans is glycogen which is composed of glucose. Starch is another example of homoglycans but it is present in plant.

There are also other groups of polysaccharides that contain molecules of more than a sugar. These polysaccharides are called heteropolysaccharides or heteroglycans. Quite a good number of heteroglycans are associated with protein and they are made of two distinct units. They are called glycoproteins. Examples of such glycoproteins are acid mucopolysaccharides and gamma globulin present in the blood plasma. Heteroglycans can also be combined with lipids and these are called glycolipids. Examples of glycolipids are gangliosides available in the central nervous system.

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