Figure 1.

(A) Representative repeating disaccharide unit of chondroitin sulfate (CS) structures. CSs are composed of alternating 4-linked β-d-glucuronic acid (GlcA) and 3-linked β-d-N-acetylgalactosamine (GalNAc) units. While CS-A is mostly 4-sulfated at the GalNAc units, CS-C is predominantly 6-sulfated [7]. While CS-D is composed of 2-sulfated GlcA and 6-sulfated GalNAc, CS-E is composed of 4,6-di-sulfated GalNAc. CS-K, CS-L and CS-M are all sulfated at C3 position of GlcA, and respectively sulfated at positions C4, C6, and simultaneously at C4 and C6. Oversulfated chondroitin sulfate (OSCS) is fully sulfated. Dermatan sulfate (DS) also known as CS-B is composed of alternating 4-linked α-L-iduronic acid (IdoA) and 3-linked β-d-GalNAc units. (B) Representative repeating trisaccharide unit of the fucosylated chondroitin sulfate (FucCS). Besides consisting of the regular CS disaccharide unit as shown at panel A, the FucCS also exhibits branching units of α-l-fucopyranose (Fucp) 3-linked to the GlcA unit as highlighted with the box in dashed lines. The detailed structure of the Fucp unit varies according to the holothurian species. In all panels the glycosidic bonds are indicated in ellipses whereas monosaccharide types are indicated in continuous black rectangles. For fast notation of the sulfation patterns, sulfation sites are highlighted by light-grey rectangles.