DefinitionThis section has been translated automatically.
Glycosaminoglycans (GAGs) represent a group of high molecular weight substances that are composed of repeating linear disaccharide units. The disaccharide repeating units consist of esters of a uronic acid, which are linked together in a 1-4-glycosidic manner. In most cases this is glucuronic acid, more rarely iduronic acid. The disaccharide units are connected 1-3-glycosidically with an amino sugar (e.g. N-acetylglucosamine). Glycosaminoglycans are often further esterified with sulphuric acid or acetic acid.
Due to the numerous hydroxyl, carboxy or sulfate group side chains, the glycosaminoglycan molecules are negatively charged. Glycosaminoglycans form glycoproteins and proteoglycans with proteins.
ClassificationThis section has been translated automatically.
Biological significance and composition of the various Subgroups of the glycosamine glycans:
Hyaluronic acid (HA) - is the only glycosaminoglycan not bound to a protein central filament. Occurrence: synovial fluid, vitreous body, umbilical cord
Heparin/heparan sulfate - consisting of D-glucuronic acid linked to the amino sugar glucosamine. The amino group of glucosamine can carry both an acetyl group and a sulphate group - glucosamine sulphate (GS)
Chondroitin-4-sulphate/dermatan sulphate, components: chondroitin sulphate A, glucuronic acid, N-acetylgalactosamine with a sulphate group at C4. Occurrence: Cartilage, large vessels
Chondroitin-6-sulfate, components: glucuronic acid, N-acetylgalactosamine with a sulfate group at C6. Occurrence: heart valves
Keratan sulfate (KS), components: galactose, N-acetylglucosamine with sulfate groups on galactose and N-acetylglucosamine. Occurrence: cornea, nucleus pulposus, cartilage.
General informationThis section has been translated automatically.
Medical: Diseases associated with disturbances in the metabolism of glycosaminoglycans (lysosomal storage diseases):
M. Pfaundler-Hurler: In autosomal recessive mutations of the α-iduronidase gene (gene locus: 4p16.3) M. Pfaundler-Hurler) of the lysosomal storage disease (mucopolysaccharidosis type I), the glycosaminoglycans dermatan sulphate and heparan sulphate are deposited lysosomally in the skin and in internal organs.
M. Hunter: In Hunter's disease, a mutation-related misexpression of the lysosomal iduronate-2-sulfatase (gene locus Xq27.3-28), there is also a disturbed degradation of the glycosaminoglycans dermatan sulfate and heparan sulfate. This results in progressive organ damage, particularly to the kidneys, liver, lungs and skeletal system.
Other diseases associated with disorders of the metabolism of glycosaminoglycans:
- Morbus Sanfilippo (MPS III)
- Morbus Morquio (MPS IV)
- Maroteaux-Lamy disease (MPS VI)
- Sly's disease (MPS VII)
The role of glycosaminoglycans in Alzheimer's disease is not yet fully understood.
Cosmetics. Glycosaminoglycans are used in cosmetic formulations. They act as emollients (make the skin supple and smooth), film formers (they form a film on skin, hair or nails when applied) and skin care products.