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.

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 class V plant chitinases have a glycosyl hydrolase family 18 (GH18) domain, but lack the chitin-binding domain present in other GH18 enzymes. The GH18 domain of the class V chitinases has endochitinase activity in some cases and no catalytic activity in others. Included in this family is a lectin found in black locust (Robinia pseudoacacia) bark, which binds chitin but lacks chitinase activity. Also included is a chitinase-related receptor-like kinase (CHRK1) from tobacco (Nicotiana tabacum), with an N-terminal GH18 domain and a C-terminal kinase domain, which is thought to be part of a plant signaling pathway. The GH18 domain of CHRK1 is expressed extracellularly where it binds chitin but lacks chitinase activity.

Crystalstructure of the GH18 chitinase ChiB from the chitin utilization locus of Flavobacterium johnsoniae [Flavobacterium johnsoniae UW101]

Crystalstructure of a class V chitinase from Arabidopsis thaliana [Arabidopsis thaliana],3AQU_B Crystal structure of a class V chitinase from Arabidopsis thaliana [Arabidopsis thaliana],3AQU_C Crystal structure of a class V chitinase from Arabidopsis thaliana [Arabidopsis thaliana],3AQU_D Crystal structure of a class V chitinase from Arabidopsis thaliana [Arabidopsis thaliana]

Crystalstructure of chitinase (RmChi1) from Rhizomucor miehei (sp p32 2 1, MR) [Rhizomucor miehei],5YUQ_A Chain A, Chintase [Rhizomucor miehei],5YUQ_B Chain B, Chintase [Rhizomucor miehei],7FBT_A Chain A, Chitinase [Rhizomucor miehei]

ChainA, Fungal chitinase from Rhizomucor miehei (SeMet-substituted proteins) [Rhizomucor miehei]

ChainA, Glycosyl Hydrolase [Niallia circulans]

Class V chitinase OS=Arabidopsis thaliana OX=3702 GN=ChiC PE=1 SV=1

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

Class V chitinase CHIT5 OS=Lotus japonicus OX=34305 GN=CHIT5 PE=1 SV=2

Endochitinase 46 OS=Trichoderma harzianum OX=5544 GN=chit46 PE=1 SV=1

Endochitinase 42 OS=Trichoderma harzianum OX=5544 GN=chit42 PE=1 SV=1