Mucopolysaccharides proteoglycan

Proteoglycans Glycosaminoglycans (mucopolysaccharides) bound to protein chains in covalent complexes. Proteoglycans are present in the extracellular matrix of connective tissue. 

Proteolytic digestion of proteoglycans liberates the carbohydrate side-chains, which are known as glycosaminoglycans (also known as mucopolysaccharides). All the glycosaminogly-cans contain derivatives of glucosamine or galactosamine. Six major groups are known, one of which is heparin. 

Hyaluronic acid is a component of the extracellular ground substance which surrounds the collagen and elastin fibres and cells of connective tissue [64], It is a member of the group of polysaccharides isolated from vertebrate connective tissues which were formerly called mucopolysaccharides and are now more commonly referred to as glycosaminoglycans [65,66], Glycosaminoglycans commonly occur in vivo as proteoglycans. 

Mucopolysaccharides absorb significant quantities of water and tend to have a mucoid, or viscous consistency. This enables them to provide a structural or lubricatory role in connective tissue. They also help to maintain fluid and electrolyte balance throughout the body. Hyaluronic acid differs from the other five types in that it has not been shown to attach along the core protein, but does provide a backbone for proteoglycan aggregates (fig. 6.5). Also, it is not sulfeted. 

F-1) The mucopolysaccharidoses are proteoglycan disorders that generally result from a hereditary lysosomal defect in enzymes that normally degrade mucopolysaccharides (in most cases heparan sulfate and dermatan sulfate). This leads to the accumulation of different mucopolysaccharides, which may be associated with a variety of different findings, commonly including mental retardation and various skeletal abnormalities. These diseases include Hunter disease, Hurler and Scheie disease, I-cell disease , Maroteaux-Laury disease, Morquio syndrome, Mucolipidoses VH disease, multiple sulfatase deficiency, and Sanfilippo A and B diseases, which will not be elaborated on further here. Often these conditions can be detected in advance on amniocentesis. 

Glycoproteins will be discussed in some detail in Section 12.4. The carbohydrate components of proteoglycans are known as glycosaminoglycans. Proteoglycans are essential parts of the connective tissue In mammals and are also present to some extent in fish and bacteria (peptidoglycans from the cell wall of bacteria are different biopolymers and were discussed in Section 7.9). The term mucopolysaccharide was used in the past to describe polysaccharide materials of animal origin containing 2-amino-2-deoxyhexoses. 

D. The mucopolysaccharides of proteoglycans contain long chains of repeating disaccharide units that are covalently linked to a protein. Sulfation occurs after the monosaccharides are incorporated into the mucopolysaccharide chain. Proteoglycans are degraded by lysosomal... 

This is strongly linked to proteoglycans and mucopolysaccharides, hyaluronic acid, and chondroitin sulfate. Silidon plays an important role in skin healing and is essential in anti-aging treatments. 

Autoradiographic studies in rats revealed that radioactivity from radiolabelled pralidoxime, obidoxime, trimedoxime and HI 6 was concentrated in the kidneys and mucopolysaccharide-containing tissue such as intervertebral discs and other cartilaginous structures. The enrichment of cationic substances in proteoglycan-rich tissue is not unusual and most probably based on ionic interactions (Garrigue et al, 1991 Maurizis et al,... 

The last review of mucopolysaccharides appeared in Advances in Clinical Chemistry in 1964. Since then, the various aspects of this field have been greatly developed, and Kennedy now presents a substantial and most comprehensive review of the chemical and biochemical aspects of glycosaminoglycans and proteoglycans, a nomenclature which he considers superior to the older terms. Of particular interest is his very extensive account of the roles of these compounds in health and disease. 

The proteoglycans contain heteropolysaccharides known as glycosaminoglycans, an unwieldy term that emphasizes their content of hexosamines and uronic acids. Formerly glycosaminoglycans were known as mucopolysaccharides. The best known members of this group are the chondroitin sulphates and hyaluronic acid. Though they are characterized by the structure of their polysaccharide chains, these are almost invariably associated with protein, hence the term proteoglycan. 

Esters with sulfuric acid often occur as components of some polysaccharides. Sugar sulfates are particularly common components in proteoglycans (mucoproteins) of animal tissues as building blocks of mucopolysaccharides. They are also components of seaweed polysaccharides agar and carrageenan. 

The storage polysaccharide in animals is glycogen. Structural functions are carried out by chitin, forming the exoskeletons of crustaceans, moUuscs and insects, and mucopolysaccharides occurring in proteoglycans of connective tissues. 

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