How do proteoglycans and glycosaminoglycan differ?
Proteoglycans are glycoproteins that contain one or more sulfated glycosaminoglycan (GAG) chains. They are classified according to their core protein, which is coded for by distinct genes.
GAGs make up part of the proteoglycans. They are classified into four types: chondroitin sulfate/dermatan sulfate, heparan sulfate/heparin, keratan sulfate, and hyaluronic acid (hyaluronan). All GAGs are sulfated except for hyaluronic acid. Hyaluronic acid is unique in that it forms in the plasma membrane (not Golgi) before release into the extracellular matrix and is widely distributed throughout the connective, epithelial, and neural tissues. It is important for cellular proliferation and migration in tissues.