InterPro domain: IPR016283

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 19 GH19 comprises enzymes with only one known activity; chitinase ( 3.2.1.14 ).

Chitinases [ 3 ] are enzymes that catalyze the hydrolysis of the beta-1,4-N-acetyl-D-glucosamine linkages in chitin polymers. Chitinases belong to glycoside hydrolase families 18 or 19 [ 4 ]. Chitinases of family 19 (also known as classes IA or I and IB or II) are enzymes from plants that function in the defence against fungal and insect pathogens by destroying their chitin-containing cell wall. Class IA/I and IB/II enzymes differ in the presence (IA/I) or absence (IB/II) of a N-terminal chitin-binding domain. The catalytic domain of these enzymes consist of about 220 to 230 amino acid residues. The At2g43600 protein from Arabidopsis thaliana is presumably inactive as a chitinase because it lacks the Glu residue that is essential for catalytic activity.

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. What's new in chitinase research? Experientia 48, 701-16
4. A classification of glycosyl hydrolases based on amino acid sequence similarities. Biochem. J. 280 ( Pt 2), 309-16