InterPro: IPR001579 Glycoside hydrolase, chitinase 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.

Chitinases (EC:3.2.1.14) [5] are enzymes that catalyse the hydrolysis of the beta-1,4-N-acetyl-D-glucosamine linkages in chitin polymers. From the view point of sequence similarity chitinases belong to either family 18 or 19 in the classification of glycosyl hydrolases [6].

Chitinases of family 18 (also known as classes III or V) groups a variety of chitinases and other proteins. Site directed mutagenesis experiments [7] and crystallographic data [8, 9] have shown that a conserved glutamate is involved in the catalytic mechanism and probably acts as a proton donor. This glutamate is the last residue of this active site signature.