Glycosyl hydrolases family 18.

Glyco_18 domain.

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 Bacteroides thetaiotaomicron protein represented by pdb structure 3CO4 is an uncharacterized bacterial member of the family 18 glycosyl hydrolases with homologs found in Flavobacterium, Stigmatella, and Pseudomonas.

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.

Crystalstructure of Ostrinia furnacalis Group II chitinase catalytic domain 1 [Ostrinia furnacalis],5Y2B_A Crystal structure of Ostrinia furnacalis Group II chitinase catalytic domain 1 in complex with HEPTA-N-ACETYLCHITOOCTAOSE (NAG)7 [Ostrinia furnacalis]

Crystalstructure of Ostrinia furnacalis Group II chitinase catalytic domain 1 in complex with a piperidine-thienopyridine derivative [Ostrinia furnacalis],6JAW_A Crystal structure of Ostrinia furnacalis Group II chitinase catalytic domain 1 in complex with a napthalimide derivative [Ostrinia furnacalis],6JAX_A Crystal structure of Ostrinia furnacalis Group II chitinase catalytic domain 1 in complex with chitooctaose [(GlcN)8] [Ostrinia furnacalis],6JAY_A Crystal structure of Ostrinia furnacalis Group II chitinase catalytic domain 1 in complex with a dipyrido-pyrimidine derivative [Ostrinia furnacalis]

Crystalstructure of Ostrinia furnacalis Group IV chitinase [Ostrinia furnacalis],6JMB_A Chain A, ofchtiv-allosamidin [Ostrinia furnacalis]

Crystalstructure of Ostrinia furnacalis Group IV chitinase [Ostrinia furnacalis]

Thecrystal structure of novel mammalian lectin Ym1 suggests a saccharide binding site [Mus musculus],1VF8_A The Crystal Structure of Ym1 at 1.31 A Resolution [Mus musculus]

Probable chitinase 2 OS=Drosophila melanogaster OX=7227 GN=Cht2 PE=1 SV=1

Chitinase-like protein 3 OS=Mus musculus OX=10090 GN=Chil3 PE=1 SV=2

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

Chitinase-like protein 4 OS=Mus musculus OX=10090 GN=Chil4 PE=1 SV=2

Acidic mammalian chitinase OS=Mus musculus OX=10090 GN=Chia PE=1 SV=2