nonreducing terminal of the blocks 6,7. The short GlcA blocks are mostly 4-sulfated, whereas longer blocks also contain 6-sulfated GalNac residues 8. The resulting CS/DS chains therefore contain different domains that enrich their functional properties. The presence of alternating IdoA-GlcA or isolated IdoA has been overlooked in many cases. Furthermore, the content of IdoA varies within the same proteoglycan depending on the tissue of expression 6 and physiological conditions 9. This is the case for decorin, which is highly iduronated in skin. In bone decorin, however, IdoA is virtually absent 6. Given the fact that a chain containing IdoA always contains GlcA, the name CS/DS indicates the hybrid nature of the chain.
