InterPro: IPR019802 Glycoside hydrolase, family 4, 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 4 GH4 comprises enzymes with several known activities; 6-phospho-beta-glucosidase (EC:3.2.1.86); 6-phospho-alpha-glucosidase (EC:3.2.1.122); alpha-galactosidase (EC:3.2.1.22).

These enzymes require NAD and a divalent ion for their activity and are proteins of about 50 kDa; e.g. 6-phospho-alpha-glucosidase requires both NAD(H) and divalent metal (Mn2+, Fe2+, Co2+, or Ni2+) for activity [5]. The signature pattern is located to a conserved region located in the central section. This region does not contain residues directly shown to be important for the catalytic activity.