InterPro domain: IPR001547

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) website.

Glycoside hydrolase family 5 GH5 comprises enzymes with several known activities; endoglucanase ( 3.2.1.4 ); beta-mannanase ( 3.2.1.78 ); exo-1,3-glucanase ( 3.2.1.58 ); endo-1,6-glucanase ( 3.2.1.75 ); xylanase ( 3.2.1.8 ); endoglycoceramidase ( 3.2.1.123 ).

The microbial degradation of cellulose and xylans requires several types of enzymes. Fungi and bacteria produces a spectrum of cellulolytic enzymes (cellulases) and xylanases which, on the basis of sequence similarities, can be classified into families. One of these families is known as the cellulase family A [ 3 ] or as the glycosyl hydrolases family 5 [ 4 ]. One of the conserved regions in this family contains a conserved glutamic acid residue which is potentially involved [ 5 ] in the catalytic mechanism.

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. Cellulase families revealed by hydrophobic cluster analysis. Gene 81, 83-95
4. A classification of glycosyl hydrolases based on amino acid sequence similarities. Biochem. J. 280 ( Pt 2), 309-16
5. Cellulase EGZ of Erwinia chrysanthemi: structural organization and importance of His98 and Glu133 residues for catalysis. Protein Eng. 4, 325-33