Term: peptidoglycan https://doi.org/10.1351/goldbook.P04480 Definition: A 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. 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. Related Terms: 1) glycosaminoglycan (http://doi.org/10.1351/goldbook.G02659). Source: PAC, 1988, 60, 1389. 'Nomenclature of glycoproteins, glycopeptides and peptidoglycans (Recommendations 1985)' on page 1391 (https://doi.org/10.1351/pac198860091389) Citation: 'peptidoglycan' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.P04480 License: The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) for individual terms. Disclaimer: The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using.