Glycome Atlas
molecule
Also known as HS, heparan sulfate glycosaminoglycan, HSGAG
IdoA (α1-4) → GlcN (repeating unit)
How to read these diagrams (SNFG)
Each shape is a class of sugar and each colour a specific one. Structures read right to left, with the reducing end (the point of attachment) on the right.
Plain-language answer
Heparan sulfate is a long, negatively charged sugar chain that is attached to certain proteins on the surface of cells. It is the most abundant sugar chain in the glycocalyx, the gel-like coating that lines blood vessels, and its many negative charges pull in water and grip passing proteins.12
Heparan sulfate helps blood flow smoothly and keeps the vessel wall from clotting or leaking. It docks a natural blood thinner called antithrombin at the vessel surface and holds growth factors in place. When these chains are stripped away during illness, the vessel lining loses much of its protective, anti-clotting character.21
Technical detail
Heparan sulfate is a linear, sulfated glycosaminoglycan built from repeating hexuronic acid and N-acetylglucosamine disaccharides that are variably modified by sulfation and epimerization, covalently attached to proteoglycan core proteins, and it is the most abundant glycosaminoglycan of the endothelial glycocalyx.12
Heparan sulfate chains are polymerized as alternating glucuronic acid and N-acetylglucosamine units, then extensively modified by N-deacetylation and N-sulfation, epimerization of glucuronic to iduronic acid, and O-sulfation at several positions. This templated but non-uniform processing creates highly sulfated domains interspersed with less modified regions, generating the sequence diversity that underlies selective protein binding.1
The mature chains are attached through a common tetrasaccharide linker to serine residues on proteoglycan core proteins, which in the vasculature include the membrane-bound syndecans and glypicans that anchor heparan sulfate to the endothelial surface.12
Within the endothelial glycocalyx heparan sulfate is the predominant glycosaminoglycan and a principal source of the layer's fixed negative charge, contributing to its role as a permeability barrier and mechanosensor. Its sulfated sequences bind antithrombin and growth factors at the luminal surface, supporting anticoagulant tone and localized signaling.21
Human relevance
Enzymatic removal of heparan sulfate from the glycocalyx releases fragments into plasma and reduces the anticoagulant, antithrombin-binding capacity of the endothelial surface, linking heparan sulfate loss to a more pro-coagulant, more permeable vessel wall.2
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References