glycosaminoglycan peptidoglycosaminoglycan CHEBI:86469 A family of glycosaminoglycan formed by alternating residues of D-glucosamine and either muramic acid {2-amino-3-O-[(S)-1-carboxyethyl]-2-deoxy-D-glucose} or L-talosaminuronic acid (2-amino-2-deoxy-L-taluronic acid), which are usually N-acetylated or N-glycoloylated. Those containing muramic acid residues are known as peptidoglycans while those containing L-talosaminuronic acid residues are known as pseudopeptidoglycans. The carboxyl group of the muramic acid is commonly substituted by a peptide containing residues of both L- and D-amino acids, whereas that of L-talosaminuronic acid is substituted by a peptide consisting of L-amino acids only.