serglycin

An intracellular proteoglycan, found particularly in the storage granules of connective tissue mast cells. The core protein consists of 153 amino acids with 24 serine-glycine repeats between amino acids 89 and 137, hence the name. The serine-glycine repeats are the linkage sites for around 15 glycosaminoglycan chains that are either heparin or highly sulphated chondroitin sulphate. These negatively charged chains are thought to concentrate positively charged proteases, histamine and other molecules within the storage granules.