Abstract
Glycosaminoglycans (GAGs) are sulfated glycans capable of regulating various biological and medical functions. Heparin, heparan sulfate, chondroitin sulfate, dermatan sulfate, keratan sulfate and hyaluronan are the principal classes of GAGs found in animals. Although GAGs are all composed of disaccharide repeating building blocks, the sulfation patterns and the composing alternating monosaccharides vary among classes. Interestingly, GAGs from marine organisms can present structures clearly distinct from terrestrial animals even considering the same class of GAG. The holothurian fucosylated chondroitin sulfate, the dermatan sulfates with distinct sulfation patterns extracted from ascidian species, the sulfated glucuronic acid-containing heparan sulfate isolated from the gastropode Nodipecten nodosum, and the hybrid heparin/heparan sulfate molecule obtained from the shrimp Litopenaeus vannamei are some typical examples. Besides being a rich source of structurally unique GAGs, the sea is also a wealthy environment of GAG-resembling sulfated glycans. Examples of these mimetics are the sulfated fucans and sulfated galactans found in brown, red and green algae, sea urchins and sea cucumbers. For adequate visualization, representations of all discussed molecules are given in both Haworth projections and 3D models.
Highlights
Sulfated glycans are a structurally complex and widely diverse class of carbohydrates
As discussed above for the marine invertebrate sulfated fucans, the sulfated galactans from sea urchins are composed of well-defined chemical structures such as the ones isolated and characterized for the species Echinometra lucunter composed of the monosaccharide repeating unit (Figure 5B) and Glyptocidaris crenularis composed of a disaccharide repeating unit (Figure 5C)
As an alternative source to these classes of sulfated glycans, the marine organisms including macroalgae and invertebrates are capable of synthesizing GAGs and GAG mimetics of very distinct structures than those seen from the terrestrial origins
Summary
Sulfated glycans are a structurally complex and widely diverse class of carbohydrates. Heparin and heparan sulfate share basically the same structural disaccharide precursor to build-up their backbones, in which different degrees of chain modification further occur according to each of these two GAG types [2,3]. Chondroitin sulfate is composed of alternating 3-linked β-D-GalNAc and 4-linked β-D-GlcA units (Figure 1C). The closely related dermatan sulfate has 4-linked α-L-iduronic acid (IdoA) instead of β-D-GlcA (Figure 1D) This happens because of C5 epimerization process during the biosynthesis of dermatan sulfate [5]. HnoolsoatchcuhriaarnidFeuscoasryeladteidspClhaoyneddrointinthSeuilrfacteommonest chair configurations: 4C1 for GlcA, GalNAc, GlcNAc Aanddis1tCin4ctfoGrAIdGoAm.olecule from the marine environment is the fucosylated chondroitin sulfate found exclusively in sea cucumbers (Echinodermata, Holothuroidea). The percentage of sulfation patterns on the lateral Fuc residues of each holothurian fucosylated chondroitin sulfate and on the IdoA and GalNAc units of the ascidian dermatan sulfates are shown as inserts at the bottom of the panels and close to the respective units
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