InterPro: IPR018087 Glycoside hydrolase, family 5, conserved site

O-Glycosyl hydrolases EC: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, 3]. This classification is available on the CAZy (CArbohydrate-Active EnZymes) web site [4]. Because the fold of proteins is better conserved than their sequences, some of the families can be grouped in clans.

Glycoside hydrolase family 5 GH5 comprises enzymes with several known activities; endoglucanase (EC:3.2.1.4); beta-mannanase (EC:3.2.1.78); exo-1,3-glucanase (EC:3.2.1.58); endo-1,6-glucanase (EC:3.2.1.75); xylanase (EC:3.2.1.8); endoglycoceramidase (EC: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 [5] or as the glycosyl hydrolases family 5 [6]. One of the conserved regions in this family contains a conserved glutamic acid residue which is potentially involved [7] in the catalytic mechanism.