The glycosyl hydrolases family 18 (GH18) [E1] is widely distributed in all
kingdoms, including viruses, bacteria, plants, fungi and animals. The GH18
family contains hydrolytic enzymes with chitinase or endo-N-acetyl-β-D-glucosaminidase (ENGase) activity as well as chitinase like lectins (chi-lectins/proteins (CLPs). Chitinases (EC 3.2.1.14) are hydrolytic enzymes that
cleave the β-1,4-bond releasing oligomeric, dimeric (chitobiose) or
monomeric (N-actetylglucosamine, GlcNAc) products. ENGases (EC 3.2.1.96)
hydrolyze the β-1,4 linkage in the chitobiose core of N-linked glycans from
glycoproteins leaving one GlcNAc residue on the substrate. CLPs do not display
chitinase activity but some of them have been reported to have specific
functions and carbohydrate binding property. The catalytic domain of GH18s may
be connected to one or several substrate binding modules (CBMs), which enhance
binding of enzymes to insoluble substrates. Certain GH18s also contain
peptide signals for localization such as an N-terminal secretion peptide, a C-terminal glycosyl-phosphatidylinositol (GPI) anchor signal for attachment to
the plasma-membrane, or N- or O-linked glycosylation sites for oligosaccharide
modifications [1,2,3,4,5,6,7,8,9].
The catalytic domain of GH18s has a common (β/α)8 triosephosphate
isomerase (TIM)-barrel structure, which consists of a barrel-like framework
made from eight internal parallel β-strands that are alternately connected
by eight exterior α helices (see <PDB:4LGX>). The active site motif
DxxDxDxE is essential for the activity of the GH18 catalytic domain. The Glu
(E) in this motif acts as the catalytic proton donor, and the last Asp (D(3))
is supposed to contribute to the stabilization of the essential distortion of
the substrate [3,4,5,6,7].
We used a region centered around the active site motif as a signature pattern
and we have also developed a profile that covers the entire GH18 catalytic
domain.
PROSITE methods (with tools and information) covered by this documentation:
References
1
Authors
Badariotti F. Lelong C. Dubos M.-P. Favrel P.
Title
Identification of three singular glycosyl hydrolase family 18 members from the oyster Crassostrea gigas: Structural characterization, phylogenetic analysis and gene expression.
Terwisscha van Scheltinga A.C. Hennig M. Dijkstra B.W.
Title
The 1.8 A resolution structure of hevamine, a plant chitinase/lysozyme, and analysis of the conserved sequence and structure motifs of glycosyl hydrolase family 18.
Tsuji H. Nishimura S. Inui T. Kado Y. Ishikawa K. Nakamura T. Uegaki K.
Title
Kinetic and crystallographic analyses of the catalytic domain of chitinase from Pyrococcus furiosus- the role of conserved residues in the active site.
Junges A. Boldo J.T. Souza B.K. Guedes R.L.M. Sbaraini N. Kmetzsch L. Thompson C.E. Staats C.C. de Almeida L.G.P. de Vasconcelos A.T.R. Vainstein M.H. Schrank A.
Title
Genomic analyses and transcriptional profiles of the glycoside hydrolase family 18 genes of the entomopathogenic fungus Metarhizium anisopliae.
PROSITE is copyrighted by the SIB Swiss Institute of Bioinformatics and
distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives
(CC BY-NC-ND 4.0) License, see prosite_license.html.
