网页Proteoglycans are proteins [1] that are heavily glycosylated. The basic proteoglycan unit consists of a "core protein " with one or more covalently attached glycosaminoglycan (GAG) chain (s). [2] The point of attachment is a serine (Ser) residue to which the glycosaminoglycan is joined through a tetrasaccharide bridge (e.g. chondroitin sulfate ...