Chondroitin, dermatan and their sulfates

4 Chondroitin, dermatan and their sulfates. Chondroitin sulfate proteoglycans have been localized to cartilage, bone, cornea and intervertebral disc, whereas dermatan sulfate is found in skin and aorta. In addition to its mechanical role, appears to have a host of regulatory functions. 

Chondroitin 4-sulfate and its uronic acid C5-epimerised isomer, dermatan 4-sulfate, occur not as free polysaccharides but as substituents on a core protein. 

Molecular modelling suggests that the conformations of chondroitin and its 6-sulfate should be very similar, with that of chondroitin 4-sulfate somewhat different because of the restrictions on j/ imposed by the sulfate group for the p-(1 3) linkage.  

The conformation of dermatan 4-sulfate, in which C5 of the glucuronic acid has been epimerised, is still unsettled. Fibre X-ray data fitted models in which the a-L-IdoA residue was in the conformation better than those in which it was in the 4 conformation. Models containing skew conformers were not considered and NMR studies have since established that in D2O solutions of dermatan 4-sulfate, the a-L-IdoA residues are in the C4 or So conformations. Molecular dynamics simulations have also supported a Sq conformation for the iduronate in dermatan sulfate.  

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