Chondroitin sulfate (CS) is a class of glycosaminoglycans that are covalently attached to proteins to form proteoglycans. Chondroitin sulfate is widely distributed in the extracellular matrix and cell surface of animal tissues. The sugar chain consists of alternating glucuronic acid and n-acetylgalactosamine (also known as n-acetylgalactosamine) disaccharide units, which are connected to the serine residue of the core protein by a saccharid-like link zone.

　　Chondroitin sulfate is present in all organisms from nematodes to humans and performs many important physiological functions except plants. Although the main chain structure of polysaccharides is not complex, the distribution of sulfation degree, sulfate group and two differences to isomeruronic acid in the chain is highly heterogeneous. The fine structure of chondroitin sulfate determines the specificity of the function and the interaction with various protein molecules.