Glycosyl hydrolases family 18.

Glyco_18 domain.

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.

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.

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.

Structureof human chitotriosidase [Homo sapiens]

Highresoultion crystal structure of human chitinase in complex with allosamidin [Homo sapiens]

CrystalStructure Of Human Chitotriosidase In Complex With Chitobiose [Homo sapiens],1LG2_A Crystal Structure Of Human Chitotriosidase In Complex With Ethylene Glycol [Homo sapiens],1LQ0_A Crystal Structure Of Human Chitotriosidase At 2.2 Angstrom Resolution [Homo sapiens],6ZE8_A Crystal structure of human chitotriosidase-1 (hCHIT) catalytic domain in complex with compound OATD-01 [Homo sapiens],6ZE8_B Crystal structure of human chitotriosidase-1 (hCHIT) catalytic domain in complex with compound OATD-01 [Homo sapiens],6ZE8_C Crystal structure of human chitotriosidase-1 (hCHIT) catalytic domain in complex with compound OATD-01 [Homo sapiens],6ZE8_D Crystal structure of human chitotriosidase-1 (hCHIT) catalytic domain in complex with compound OATD-01 [Homo sapiens],6ZE8_E Crystal structure of human chitotriosidase-1 (hCHIT) catalytic domain in complex with compound OATD-01 [Homo sapiens],6ZE8_F Crystal structure of human chitotriosidase-1 (hCHIT) catalytic domain in complex with compound OATD-01 [Homo sapiens]

Crystalstructure of human chitinase in complex with glucoallosamidin B [Homo sapiens],1HKJ_A Crystal structure of human chitinase in complex with methylallosamidin [Homo sapiens],1HKM_A High resolution crystal structure of human chitinase in complex with demethylallosamidin [Homo sapiens]

Crystalstructure of human chitotriosidase-1 catalytic domain at 1.0 A resolution [Homo sapiens],4WK9_A Crystal structure of human chitotriosidase-1 catalytic domain in complex with chitobiose (0.3mM) at 1.10 A resolution [Homo sapiens],4WKA_A Crystal structure of human chitotriosidase-1 catalytic domain at 0.95 A resolution [Homo sapiens],4WKF_A Crystal structure of human chitotriosidase-1 catalytic domain in complex with chitobiose (2.5mM) at 1.10 A resolution [Homo sapiens],4WKH_A Crystal structure of human chitotriosidase-1 catalytic domain in complex with chitobiose (1mM) at 1.05 A resolution [Homo sapiens],5NR8_A Crystal structure of human chitotriosidase-1 (hCHIT) catalytic domain in complex with compound 7a [Homo sapiens],5NRA_A Crystal structure of human chitotriosidase-1 (hCHIT) catalytic domain in complex with compound 7g [Homo sapiens],5NRF_A Crystal structure of human chitotriosidase-1 (hCHIT) catalytic domain in complex with compound 7i [Homo sapiens]

Chitotriosidase-1 OS=Homo sapiens OX=9606 GN=CHIT1 PE=1 SV=1

Chitinase 1 OS=Aphanocladium album OX=12942 GN=CHI1 PE=1 SV=2

Chitinase-3-like protein 1 OS=Mus musculus OX=10090 GN=Chi3l1 PE=1 SV=3

Probable endochitinase OS=Caenorhabditis elegans OX=6239 GN=cht-1 PE=1 SV=1

Endochitinase OS=Manduca sexta OX=7130 PE=2 SV=1