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.

Chitinase, GH18 family [Carbohydrate transport and metabolism].

Glyco_18 domain.

Glycosyl hydrolases family 18.

This conserved domain family includes a large number of catalytically inactive chitinase-like lectins (chitolectins) including YKL-39, YKL-40 (HCGP39), YM1, oviductin, and AMCase (acidic mammalian chitinase), as well as catalytically active chitotriosidases. The conserved domain is an eight-stranded alpha/beta barrel fold belonging to the family 18 glycosyl hydrolases. The fold has a pronounced active-site cleft at the C-terminal end of the beta-barrel. The chitolectins lack a key active site glutamate (the proton donor required for hydrolytic activity) but retain highly conserved residues involved in oligosaccharide binding. Chitotriosidase is a chitinolytic enzyme expressed in maturing macrophages, which suggests that it plays a part in antimicrobial defense. Chitotriosidase hydrolyzes chitotriose, as well as colloidal chitin to yield chitobiose and is therefore considered an exochitinase. Chitotriosidase occurs in two major forms, the large form being converted to the small form by either RNA or post-translational processing. Although the small form, containing the chitinase domain alone, is sufficient for the chitinolytic activity, the additional C-terminal chitin-binding domain of the large form plays a role in processing colloidal chitin. The chitotriosidase gene is nonessential in humans, as about 35% of the population are heterozygous and 6% homozygous for an inactivated form of the gene. HCGP39 is a 39-kDa human cartilage glycoprotein thought to play a role in connective tissue remodeling and defense against pathogens.

CrystalStructure Analysis of Chitinase A from Vibrio harveyi with novel inhibitors - apo structure [Vibrio harveyi],3ARP_A Crystal Structure Analysis of Chitinase A from Vibrio harveyi with novel inhibitors - complex structure with DEQUALINIUM [Vibrio harveyi],3ARQ_A Crystal Structure Analysis of Chitinase A from Vibrio harveyi with novel inhibitors - complex structure with IDARUBICIN [Vibrio harveyi],3ARR_A Crystal Structure Analysis of Chitinase A from Vibrio harveyi with novel inhibitors - complex structure with PENTOXIFYLLINE [Vibrio harveyi],3ARV_A Crystal Structure Analysis of Chitinase A from Vibrio harveyi with novel inhibitors - complex structure with Sanguinarine [Vibrio harveyi],3ARW_A Crystal Structure Analysis of Chitinase A from Vibrio harveyi with novel inhibitors - complex structure with chelerythrine [Vibrio harveyi],3ARX_A Crystal Structure Analysis of Chitinase A from Vibrio harveyi with novel inhibitors - complex structure with Propentofylline [Vibrio harveyi],3ARY_A Crystal Structure Analysis of Chitinase A from Vibrio harveyi with novel inhibitors - complex structure with 2-(imidazolin-2-yl)-5-isothiocyanatobenzofuran [Vibrio harveyi],3ARZ_A Crystal Structure Analysis of Chitinase A from Vibrio harveyi with novel inhibitors - complex structure with 2-(imidazolin-2-yl)-5-isothiocyanatobenzofuran [Vibrio harveyi],3B8S_A Crystal structure of wild-type chitinase A from Vibrio harveyi [Vibrio harveyi],3B8S_B Crystal structure of wild-type chitinase A from Vibrio harveyi [Vibrio harveyi]

ChainA, Chitinase A [Vibrio harveyi],3B9D_A Chain A, Chitinase A [Vibrio harveyi],3B9E_A Chain A, Chitinase A [Vibrio harveyi]

ChainA, Chitinase [Ostrinia furnacalis],7VRG_B Chain B, Chitinase [Ostrinia furnacalis]

ChainA, Glycosyl Hydrolase [Niallia circulans]

CrystalStructure Analysis of Chitinase A from Vibrio harveyi with novel inhibitors - apo structure of mutant W275G [Vibrio harveyi],3ART_A Crystal Structure Analysis of Chitinase A from Vibrio harveyi with novel inhibitors - W275G mutant complex structure with DEQUALINIUM [Vibrio harveyi],3ARU_A Crystal Structure Analysis of Chitinase A from Vibrio harveyi with novel inhibitors - W275G mutant complex structure with PENTOXIFYLLINE [Vibrio harveyi],3AS0_A Crystal Structure Analysis of Chitinase A from Vibrio harveyi with novel inhibitors - W275G mutant complex structure with Sanguinarine [Vibrio harveyi],3AS1_A Crystal Structure Analysis of Chitinase A from Vibrio harveyi with novel inhibitors - W275G mutant complex structure with chelerythrine [Vibrio harveyi],3AS2_A Crystal Structure Analysis of Chitinase A from Vibrio harveyi with novel inhibitors - W275G mutant complex structure with Propentofylline [Vibrio harveyi],3AS3_A Crystal Structure Analysis of Chitinase A from Vibrio harveyi with novel inhibitors - W275G mutant complex structure with 2-(imidazolin-2-yl)-5-isothiocyanatobenzofuran [Vibrio harveyi]

Chitinase A OS=Pseudoalteromonas piscicida OX=43662 GN=chiA PE=1 SV=1

Chitinase OS=Autographa californica nuclear polyhedrosis virus OX=46015 GN=CHIA PE=1 SV=1

Probable endochitinase OS=Orgyia pseudotsugata multicapsid polyhedrosis virus OX=262177 GN=ORF124 PE=3 SV=1

Chitinase A1 OS=Niallia circulans OX=1397 GN=chiA1 PE=1 SV=1

Chitinase A OS=Serratia marcescens OX=615 GN=chiA PE=1 SV=3