True GP Proteoglycans

Irregular simple simple protein regular carbohydrates

Carbohydrates protein

True (proper) GP

In structure of prosthetic groups of proper GP enter various monosaccarides and aminoderivates of them: glucoseamine, galactoseamine, neuraminic, sialic acid in various combinations and parities (ratio).

The representatives of proper (true) GP are immunoglobulins, mucins, sialoproteins, hormones, protrombin, transcortin, ceruloplasmin, haptoglobine and protein of blood`s group specificity.

Mucins – proteins of slime is contained in a saliva (they provide high viscosity of one), promoting of covering of the food, in a secret of all glands of gastro-intestenal tract, respiratory ways, urinesexual system where they carry out a protective role, in slime of fish, frogs and other reptiles, where they protect a surface of body from the harmful external factors. In prosthetic groups of mucin of man enter syalic acids, acetylgalactosamine, galactose, fucose. The molecules of mucin jointing each other form structures of significant extent strongly holding water and having by significant viscosity.

The blood group substances (antigens) (BGA)

The blood group antigens are oligosaccarides of specific medical interest. Their structures studied well. In 1900 Landsteiner described the ABO blood group. Today there are more than 20 blood group systems expressing 160 distinct antigens. The most commonly studied blood groups are those of ABH (0). These erythrocyte antigens are linked to specific membran proteins by O-glycosidic bonds in which GALNAC (acettylgalactoseamine) is the most sugar residue on a structure of prosthetic group. BGA concern to propers GP, but different from them the high content of carbohydrates (85%).

The protein consist of two/third of four aminoacids: treonine, proline, serine, alanine.

Antigen activity of these proteins is determined by the following sequences of carbohydrates on the ends of carbohydrate chain – D-galactose – N acetylglucosamine – D-galactose – N – acetylgalactoseamine.

For antigen H to this sequence fucose is jointed, for antigen A – fucose and N- acetylgalactoseamine, for antigen B – fucose and galactose.

Individuals possessing both an A and a B antigens can generate both oligosaccarides

Proteoglycans

There is another class of complex macro molecules that can contain as much as 95% or more carbohydrate, with properties that may resemble those of polysaccharides more than proteins. To distinguish these compounds from other glycoproteins, they are referred to as proteoglycans.Their carbohydrate' chains are called glycosaminoglycansor by their older name, mucopolysaccharides,especially in reference to the group of storage diseases, mucopolysaccharidosis, which result from an inability to degrade these molecules.

Proteoglycans are high molecular weight polyanionic compounds consisting of many different glycosaminoglycan chains linked covalently to a protein core. Although six distinct classes of glycosaminoglycans are now recognized, certain features are common to all classes. The long unbranched heteropolysaccharide chains are made up largely of disaccharide repeating units, in which one sugar is a hexosamine and the other a uronic acid. Other common constituents of glycosaminoglycans are sulfate groups, linked by ester bonds to certain monosaccharides or by amide bonds to the amino group of glucosamine. However, hyaluronate is not sulfated and is not covalently attached to protein. The carboxyls of uronic acids and sulfate groups contribute to the highly charged polyanionic nature of glycosaminoglycans. Both their electrical charge and macromolecular structure aid in their biological role as lubricants and support elements in connective tissue. Glycosaminoglycans are predominantly components of the extracellular matrix and cell surfaces, and increasingly more dynamic roles in cell adhesion and signaling, as well as a host of other biological activities, have been elucidated for the proteoglycans.

There are 6 types of glucosaminoglycans: hyaluronic acid, chondroitin sulfates A, B, C, D, keratin sulfates and heparines. They differ each from other by nature of uronic acids, hexosamines, by quantity of residues of sulphuric acid chemical lincages between monosaccarides, molecular masses, properties.