Heparan sulfate/heparin (HS-GAG) metabolism

Proteins carrying a heparan sulfate (HS) chain are called heparan sulfate proteoglycans (HSPG). Free HS is usually stored within the secretory granules of mast cells or cleaved from HSPGs on degradation. HS is a member of the glycosaminoglycan (GAG) family and consists of the variably sulfated repeating disaccharide units heparan (Ido-GlcNAc) or heparosan (GlcA-GlcNAc). Higher degrees of sulfation and iduronic acid content in the polysaccharide chain confers the name heparin rather than heparan sulfate to the chain. Two or three HS chains attach to a core protein on the cell surface or in the extracellular matrix. HS bound to a core protein can regulate many biological processes such as angiogenesis, blood coagulation and tumour metastasis. Degradation of HS is required to maintain a natural turnover of GAGs. Defects in the degradative enzymes result in lysosomal storage diseases, where GAGs build up rather than being broken down and having pathological effects.

Summary from Reactome (R-HSA-1638091), read 2026-09-23.