Back to article: Characterising glycosaminoglycans in human breastmilk and their potential role in infant health
FIGURE 3: Simplified schematic representation of GAG synthesis in human breastmilk. UPD sugars are synthesised in the cytoplasm where they remain until biosynthesis begins. Left: non-sulphated hyaluronic acid; UPD sugars diffuse into the plasma membrane where they are polymerised by hyaluronic acid synthases, forming the HA polysaccharide. HA is then excreted unmodified into the pericellular space 30. Right: sulphated GAG synthesis of CS, DS, Hep and HS; UPD sugars are transferred to the cis Golgi by transmembrane nucleotide transporters where they act as sugar donors for glycosyltransferases 29, 30. Synthesis of the common linkage tetrasaccharide on the proteoglycan core begins in the endoplasmic reticulum (ER) and finishes in the Golgi apparatus, allowing for CS and Hep/HS chain building. CS, Hep and HS undergo sulphation and modifications in the Golgi before secretion at the trans-golgi network 30. Created with Biorender.com.
29. Treasure Island (FL): StatPearls Publishing
30. Drug-Mediated Regulation of Glycosaminoglycan Biosynthesis. Med Res Res 37(5): 1051–1094. doi: 10.1002/med.21429