The Glycosaminoglycans , Also known as mucopolysaccharides, are glucose structures, with a function of structural biomolecules that we can find mainly in connective tissue, bone tissue, intercellular medium and epithelial tissue.
They are long chains of complex polysaccharides or proteoglycans, composed of repetitive disaccharide units.
Glycosaminoglycans are highly polar and have the capacity to attract water, so they are suitable for the biological functions they perform. They are also used as lubricants or to absorb impacts. Each is composed of hexosamine and a hexose, or hyaluronic acid.
Glycosaminoglycans are the major component of the extracellular matrix of the molecules in animal tissues and play a fundamental role in different physiological events. Not only can we find these compounds in vertebrates, but also in many invertebrates. Its function is conservation in the animal kingdom.
Several 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 humans. This determines their active and fundamental participation in biological processes.
In the case of hyaluronic acid, the human organism is present in the umbilical cord, connective tissue, synovial fluid, cartilage, blood vessels and vitreous humor (the gelatinous mass that lies between the lens and the retina in the eye); While in nature it only exists in molluscs.
Another difference is that chondroitin sulphate in the organism exists in bone and cartilage tissues, whereas in other less evolved animals it is limited, 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 of these GAG's are confirmed by chains alternating units of an amino sugar and a hyaluronic acid, which may be glucuronic acid or iduronic acid.
On the other hand, the amino sugar units may be N-acetylglucosamine or N-acetylgalactosamine.
Although the pillars of GAG's are usually always the same, polysaccharides, the repetitive lines of 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 the uronates, constituting the bases of the wide variety of structures with biological activities related to GAG's.
The presence of these biomolecules in nature, both vertebrate and invertebrate, has been well documented. In contrast, GAGs have never been found in plants.
In some bacterial chains polysaccharides synthesized with the same pillar structure as 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 the protein nuclei and form the proteoglycans. Thus, bacterial polysaccharides are different.
There is a wide structural variety in GAG's belonging to vertebrates. From fish and amphibians to mammals, the structure of these biomolecules is extremely heterogeneous.
The biosynthesis of the structural complex of the GAGs is regulated and the different patterns of sulfation are formed in an organ and in a specific tissue, temporarily during growth and development.
In fact, mutation defects in many genes of the biosynthetic enzymes of GAG's have severe consequences on vertebrate organisms. This is why the expression of GAG's and their specific sulfated structures play a fundamental role in life.
Functions of glycosaminoglycans
Their function is essential since they are fundamental components of the connective tissues, and the chains of GAG's are linked through covalent bonds to other proteins like 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 the GAG's proteins, it can stop the process of this disease or others such as inflammatory processes and infectious diseases, where GAG's act as receptors for some viruses, such as dengue, flavivirus type.
The GAG's also belong to the three components of the dermis, the layer 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, tissue regeneration and elimination of toxins from the body.
GAG's are substances that draw water into the deeper layers of the skin. One of the best known glycosaminoglycans is hyaluronic acid, present in multiple anti-aging and skin care products. The idea of these creams, lotions and tonics is to increase hydration in the skin reducing wrinkles and lines of expression.
In addition to being able to retain water, GAG's also have high viscosity and low understanding, making them ideal for protecting joints of bones in joints.
This is why synovial fluid, articular cartilage, heart valves (chondroitin sulfate, the most abundant GAG in the body), skin, pulmonary arteries and liver (heparin, which has an anticoagulant function), tendons and lungs (Dermatan sulfate) and cornea and bones (keratan sulfate).
- Evolution of glycosaminoglycans. Comparative biochemical study. Retrieved from ncbi.nlm.nih.gov.
- Special Issue"Glycosaminoglycans and Their Mimetics". Retrieved from mdpi.com.
- Manipulation of cell surface macromolecules by flaviviruses. Robert Anderson, in Advances in Virus Research, 2003. Retrieved from sciencedirect.com.
- Collagen, Elastin, and Glycosaminoglycans. Retrieved from justaboutskin.com.