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Glycoside Hydrolase Family 18
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- Author: ^^^Gideon Davies^^^
- Responsible Curator: ^^^Gideon Davies^^^
Glycoside Hydrolase Family GH18 | |
Clan | GH-K |
Mechanism | retaining/inverting |
Active site residues | known/not known |
CAZy DB link | |
http://www.cazy.org/fam/GH18.html |
Substrate specificities
GH18 is unusual in having both catalytically active chitinase (EC 3.2.1.14) and endo-β-N-acetylglucosaminidases (EC 3.2.1.96) but there are also sub-families of non-hydrolytic proteins that function as carbohydrate binding modules / "lectins" or as xylanase inhibitors.
Kinetics and Mechanism
Content is to be added here.
Catalytic Residues
The catalytically active GH18 enzymes use a double displacement reaction mechanism with "neighbouring group participation".
Three-dimensional structures
Content is to be added here.
Family Firsts
- First sterochemistry determination
- Often incorrectly reported as inverting, this family performs catalysis with retention of anomeric configuration as first shown on the Bacillus ciculans enzyme [1].
- First catalytic nucleophile identification
- Cite some reference here, with a short (1-2 senetence) explanation [2].
- First general acid/base residue identification
- Cite some reference here, with a short (1-2 senetence) explanation [3].
- First 3-D structure
- The first two 3-D structures for GH18 members were the Serratia marcescens chitinase A and the plant defence protein hevamine published "back-to-back" in Structure in 1994 [4, 5].
References
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Sinnott, M.L. (1990) Catalytic mechanisms of enzymic glycosyl transfer. Chem. Rev. 90, 1171-1202. DOI: 10.1021/cr00105a006
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- Robert V. Stick and Spencer J. Williams. (2009) Carbohydrates. Elsevier Science.