Glycosaminoglycans (GAGs), also known as mucopolysaccharides, are negatively-charged polysaccharide compounds. They are composed of repeating disaccharide units that are present in every mammalian tissue. (Biochemistry, Glycosaminoglycans - StatPearls - NCBI - NIH:https://www.ncbi.nlm.nih.gov/books/NBK544295/)