<p>O-Glycosyl hydrolases <db_xref db="EC" dbkey="3.2.1."/> are a widespread group of enzymes that hydrolyse the glycosidic bond between two or more carbohydrates, or between a carbohydrate and a non-carbohydrate moiety. A classification system for glycosyl hydrolases, based on sequence similarity, has led to the definition of 85 different families [<cite idref="PUB00004870"/>, <cite idref="PUB00005266"/>]. This classification is available on the CAZy (CArbohydrate-Active EnZymes) web site.</p><p>Glycoside hydrolase family 24 <db_xref db="CAZY" dbkey="GH24"/> comprises enzymes with only one known activity; lysozyme (<db_xref db="EC" dbkey="3.2.1.17"/>).</p><p>This entry includes <taxon tax_id="10710">Bacteriophage lambda</taxon> lysozyme and <taxon tax_id="562">Escherichia coli</taxon> endolysin [<cite idref="PUB00003216"/>]. Lysozyme helps to release mature phage particles from the cell wall by breaking down the peptidoglycan. The enzyme hydrolyses the 1,4-beta linkages between N-acetyl-D-glucosamine and N-acetylmuramic acid in peptidoglycan heteropolymers of prokaryotic cell walls. E. coli endolysin also functions in bacterial cell lysis and acts as a transglycosylase. The <taxon tax_id="10665">Bacteriophage T4</taxon> lysozyme structure contains 2 domains, the interface between which forms the active-site cleft. The N terminus of the 2 domains undergoes a 'hinge-bending' motion about an axis passing through the molecular waist [<cite idref="PUB00003216"/>, <cite idref="PUB00004082"/>]. This mobility is thought to be important in allowing access of substrates to the enzyme active site.</p>