Glycosaminoglycans characteristics and functions

1110
Egbert Haynes

The glycosaminoglycans, Also known as mucopolysaccharides, they are carbohydrate structures, with a function of structural biomolecules that can be found mainly in connective tissue, bone tissue, intercellular medium and epithelial tissue. They are long chains of complex polysaccharides or proteoglycans, made up of repeating units of disaccharides.

Glycosaminoglycans are highly polar and have the ability to attract water, making them ideal for the biological functions they perform. They are also used as lubricants or to absorb impacts. Each is made up of hexosamine and a hexose, or hyaluronic acid..

Structure of glycosaminoglycans

Article index

  • 1 Features
  • 2 Presence of glycosaminoglycans
  • 3 Functions of glycosaminoglycans
  • 4 References

Characteristics

Glycosaminoglycans are the largest component of the extracellular matrix of molecules in animal tissues and play a fundamental role in different physiological events. We can not only find these compounds in vertebrates, but also in many invertebrates. Its function is conservation in the animal kingdom.

Various sulfated structures of heparin, a glycosaminoglycan found in the liver, skin and lung, can be found in different types of organisms, from the most primitive to human beings. This determines their active and fundamental participation in biological processes..

In the case of hyaluronic acid, in the human body we find it present in the umbilical cord, connective tissue, synovial fluid, cartilage, blood vessels and vitreous humor (the gelatinous mass that is found between the lens and the retina in the eye); while in nature it only exists in mollusks.

Another difference is that chondroitin sulfate in the body exists in bone tissues and cartilage, while in other less evolved animals it is found in limited form, depending on the structural complexity of the individual and its association with certain functions..

Presence of glycosaminoglycans

In nature, we find glycosaminoglycans (GAGs) with fundamental functions in cell growth, differentiation, cell migration, morphogenesis and viral or bacterial infections..

In vertebrates, the major glycosaminoglycans are heparin or heparin sulfate, chondroitin sulfate, dermatan sulfate, and hyaluronic acid. All these GAG's are confirmed by chains that alternate units of an amino sugar and a hyaluronic acid, which can be glucuronic acid or iduronic acid..

On the other hand, the amino sugar units can be N-acetylglucosamine or N-acetylgalactosamine..

Although the pillars of the GAGs are usually always the same, polysaccharides, the repetitive lines of the heparin and chondroitin-sulfate chains require a considerable degree of structural variation.

This is due to the constant modifications that include sulphation and epemerization of uronates, constituting the bases of the wide variety of structures with biological activities related to GAGs..

The presence of these biomolecules in nature, both in vertebrate and invertebrate organisms, has been well documented. In contrast, GAG's have never been found in plants..

In some bacteria chains, synthesized polysaccharides with the same pillar structure of the GAGs are observed, but these similar polysaccharides are not bound to core proteins and are only produced on the inner surface of the cytoplasmic membrane..

In the case of GAGs in animal cells, they are added to protein nuclei and form proteoglycans. Thus, bacterial polysaccharides are different.

There is a wide structural variety in GAGs that belong to vertebrates. From fish and amphibians to mammals, the structure of these biomolecules is extremely heterogeneous.

The biosynthesis of the structural complex of GAG's is regulated and the different patterns of sulfation are formed in a specific organ and tissue, temporarily during growth and development..

In fact, mutational defects in many genes of the GAG's biosynthetic enzymes have severe consequences in vertebrate organisms. This is why the expression of GAGs and their specific sulphated structures play a fundamental role in life..

Glycosaminoglycan functions

Their function is essential since they are fundamental components of connective tissues, and the chains of the GAGs are linked through covalent bonds to other proteins such as cytokines and chemokines..

Another characteristic is that they are linked to antithrombin, a protein related to the coagulation process, so they can inhibit this function, which makes them essential in cases of treatment for thrombosis, for example.

This is also interesting in the field of cancer research. By being able to inhibit the binding of GAG's proteins, the process of this disease or others such as inflammatory processes and infectious diseases can be stopped, where GAGs act as receptors for some viruses, such as dengue, of the flavivirus type..

GAGs also belong to the three components of the dermis, the layer located under the epidermis of the skin, along with collagen and elastin. These three elements form the system known as the extracellular matrix, which allows, among other things, the regeneration of tissues and elimination of toxins from the body..

GAG's are the substances that attract water to the deeper layers of the skin. One of the best known glycosaminoglycans is hyaluronic acid, present in many anti-aging and skin care products. The idea of ​​these creams, lotions and tonics is to increase hydration in the skin by reducing wrinkles and expression lines.

In addition to being able to retain water, GAGs also have high viscosity and low compression, making them ideal for protecting the union of bones in the joints..

That is why they are present in synovial fluid, joint cartilage, heart valves (chondroitin sulfate, the most abundant GAG in the body), skin, pulmonary arteries and in the liver (heparin, which has an anticoagulant function), tendons and lungs (dermatan sulfate) and cornea and bones (kerathan sulfate).

References

  1. Evolution of glycosaminoglycans. Comparative biochemical study. Recovered from ncbi.nlm.nih.gov.
  2. Special Issue "Glycosaminoglycans and Their Mimetics". Recovered from mdpi.com.
  3. Manipulation of cell surface macromolecules by flaviviruses. Robert Anderson, in Advances in Virus Research, 2003. Recovered from sciencedirect.com.
  4. Collagen, Elastin, and Glycosaminoglycans. Recovered from justaboutskin.com.

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