Proteoglycans represent a special class of glycoproteins that are heavily glycosylated. They consist of a core protein with one or more covalently attached glycosaminoglycan (GAG) chain(s). These glycosaminoglycan chains are long, linear carbohydrate polymers that are negatively charged under physiological conditions, due to the occurrence of sulfate and uronic acid groups. Types Proteoglycans can be categorised depending upon the nature of their glycosaminoglycan chains. These chains may be: ch… (More on Proteoglycan)