The GH18 (glycosyl hydrolase, family 18) type II chitinases hydrolyze chitin, an abundant polymer of beta-1,4-linked N-acetylglucosamine (GlcNAc) which is a major component of the cell wall of fungi and the exoskeleton of arthropods. Chitinases have been identified in viruses, bacteria, fungi, protozoan parasites, insects, and plants. The structure of the GH18 domain is an eight-stranded beta/alpha barrel with a pronounced active-site cleft at the C-terminal end of the beta-barrel. The GH18 family includes chitotriosidase, chitobiase, hevamine, zymocin-alpha, narbonin, SI-CLP (stabilin-1 interacting chitinase-like protein), IDGF (imaginal disc growth factor), CFLE (cortical fragment-lytic enzyme) spore hydrolase, the type III and type V plant chitinases, the endo-beta-N-acetylglucosaminidases, and the chitolectins. The GH85 (glycosyl hydrolase, family 85) ENGases (endo-beta-N-acetylglucosaminidases) are closely related to the GH18 chitinases and are included in this alignment model.
Bacteroidetes-Associated Carbohydrate-binding (putative) Often N-terminal (BACON) domain. The BACON domain is found in diverse domain architectures and accociated with a wide variety of domains, including carbohydrate-active enzymes and proteases. It was named for its suggested function of carbohydrate binding; the latter was inferred from domain architectures, sequence conservation, and phyletic distribution. However, recent experimental data suggest that its primary function in Bacteroides ovatus endo-xyloglucanase BoGH5A is to distance the catalytic module from the cell surface and confer additional mobility to the catalytic domain for attack of the polysaccharide. No evidence for a direct role in carbohydrate binding could be found in that case. The large majority of BACON domains are found in Bacteroidetes.
The GH18 (glycosyl hydrolases, family 18) type II chitinases hydrolyze chitin, an abundant polymer of N-acetylglucosamine and have been identified in bacteria, fungi, insects, plants, viruses, and protozoan parasites. The structure of this domain is an eight-stranded alpha/beta barrel with a pronounced active-site cleft at the C-terminal end of the beta-barrel.