InterPro: IPR019800 Glycoside hydrolase, family 3, active 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 3 GH3 comprises enzymes with a number of known activities; beta-glucosidase (EC:3.2.1.21); beta-xylosidase (EC:3.2.1.37); N-acetyl beta-glucosaminidase (EC:3.2.1.52); glucan beta-1,3-glucosidase (EC:3.2.1.58); cellodextrinase (EC:3.2.1.74); exo-1,3-1,4-glucanase (EC:3.2.1). These enzymes are two-domain globular proteins that are N-glycosylated at three sites [5]. This domain is often N-terminal to the glycoside hydrolase family 3, C-terminal domain IPR002772.

The signature pattern in these enzymes is centred on a conserved aspartic acid residue which has been shown [6], in Aspergillus wentii beta-glucosidase A3, to be implicated in the catalytic mechanism.