Sulfated Glycans and Related Digestive Enzymes in the Zika Virus Infectivity: Potential Mechanisms of Virus-Host Interaction and Perspectives in Drug Discovery

Figure 1

Structural representation of (a) heparan sulfate (HS) and (b) chondroitin sulfate (CS) and subtypes. (a) The repeating disaccharide unit of HS is composed of alternating 4-linked uronic acid and 4-linked -glucosamine (GlcNX) units. The uronic acid can be either -D-glucuronic acid (GlcA) as its major component or -L-glucuronic acid (IdoA). Regarding possible substitutions, the GlcNX units are frequently N-acetylated (GlcNAc), occasionally N-sulfated (GlcNS), and rarely N-free (just the amino NH₂ group, as GlcN). O-sulfation can occur at both units of HS. While 2-O-sulfation occurs occasionally at the IdoA, 6-O-sulfation is common at the GlcNS units. 3-O-sulfation may also occur at the occasional GlcNS6S unit but very rarely in terms of amounts. (b) The repeating disaccharide unit of CS is composed of alternating 4-linkedβ-D-glucuronic acid (GlcA) and 3-linked -D-galactosamine (GalNAc) units. The CS subtypes differ according to sulfation patterns as follows: CS-A is mostly 4-O-sulfated at the GalNAc units, CS-C is predominantly 6-O-sulfated at the GalNAc units, CD-D is mostly 2-O-sulfated at the GlcA units and 6-O-sulfated at the GalNAc units, and CS-E is mostly 4,6-O-disulfated at the GalNAc units. In both panels, the glycosidic bonds are indicated inside the ellipses, whereas monosaccharide types are indicated inside the rectangles. For fast notation of the sulfation patterns, sulfation sites are highlighted by light-grey shadowed rectangles.

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