O-Glycosyl hydrolases (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 [1, 2]. This classification is available on the CAZy (CArbohydrate-Active EnZymes) web site.
Glycoside hydrolase family 24 GH24 comprises enzymes with only one known activity; lysozyme (3.2.1.17).
This entry includes Bacteriophage lambda lysozyme and Escherichia coli endolysin [3]. 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 Bacteriophage T4 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 [4, 4]. This mobility is thought to be important in allowing access of substrates to the enzyme active site.
1. Conserved catalytic machinery and the prediction of a common fold for several families of glycosyl hydrolases. Proc. Natl. Acad. Sci. U.S.A. 92, 7090-4
2. Structures and mechanisms of glycosyl hydrolases. Structure 3, 853-9
3. Structure of bacteriophage T4 lysozyme refined at 1.7 A resolution. J. Mol. Biol. 193, 189-99
4. A mutant T4 lysozyme displays five different crystal conformations. Nature 348, 263-6
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