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 [PMID:7624375, PMID:8535779, PUB00005672]. This classification is available on the CAZy (CArbohydrate-Active EnZymes) web site [PUB00007032]. Because the fold of proteins is better conserved than their sequences, some of the families can be grouped in 'clans'.

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 [PMID:1747104, PMID:8352747, PMID:8687420, PMID:1732212, PMID:8535779, PUB00005672]. This classification is available on the CAZy (CArbohydrate-Active EnZymes) web site [PUB00007032]. Because the fold of proteins is better conserved than their sequences, some of the families can be grouped in 'clans'.

Glycoside hydrolase family 19 CAZY: GH_19 comprises enzymes with only one known activity; chitinase (EC: 3.2.1.14).

Chitinases [PMID:1516675] 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 [PMID:1747104]. Chitinases of family 19 (also known as classes IA or I and IB or II) are enzymes from plants that function in the defense 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.