The acronym HS-GAG is used to describe both heparin and heparan sulfate. HS-GAG is a member of the glycosaminoglycan family and consists of a variably sulfated repeating disaccharide unit, the most common one (50% of the total) being glucuronic acid (GlcA) linked to N-acetylglucosamine (GlcNAc). GlcA can be epimerized to iduronic acid. Higher degrees of sulfation and iduronic acid content in the polysaccharide chain confers the name heparin rather than heparan sulfate to the chain. HS-GAG, like the majority of GAGs in the body, are linked to core proteins, forming proteoglycans (mucopolysaccharides). Two or three HS-GAG chains attach to a core protein on the cell surface or in the extracellular matrix (Sasisekharan & Venkataraman 2000). HS-GAG bound to a core protein can regulate many biological processes such as angiogenesis, blood coagulation and tumour metastasis (Stringer & Gallagher 1997, Tumova et al. 2000). Degradation of HS-GAG 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 (Ballabio & Gieselmann 2009).