Glycoside Hydrolase Family 80

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• Author: Ryszard Brzezinski
• Responsible Curator: Ryszard Brzezinski

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Glycoside Hydrolase Family GH80
Clan	GH-I
Mechanism	not determined
Active site residues	inferred
CAZy DB link
http://www.cazy.org/GH80.html

Substrate specificities

Glycoside hydrolase family GH80 is comprised of endo-acting β-1,4-chitosanases of bacterial origin. The first characterized member was from a proteobacterium [1] belonging to the Bacteroidetes/Chlorobi group [2, 3]. At present (July 2011), GH80 is very small family, comprised of fewer than 20 members.

Characterized GH80 members do not hydrolyze chitin or cellulose [1, 3], and for one member, the chitosan hexa-oligosaccharide (GlcN)₆ is preferentially hydrolyzed into two molecules of the trisaccharide [4].

Kinetics and Mechanism

The stereochemistry of the hydrolytic reaction catalyzed by GH80 members has not yet been studied. However, sequence similarity with members of Clan GH-I suggests that these enzymes may operate with inversion of the anomeric configuration (see Catalytic Residues, below)

Catalytic Residues

The chitosanases from family GH80 share a PROSITE signature motif [5] with the chitosanases from family GH46 [6]. Together with GH24, these three families comprise clan GH-I [7].

A site-directed mutagenesis study of the chitosanase A from Matsuebacter chitosanotabidus 3001 (new name: Mitsuaria chitosanitabida [8]) identified two residues as essentiel for catalysis: Glu-121 (in the sequence YPENG)and Glu-141 (in the sequence DYEAA) [4].

Three-dimensional structures

No three-dimensional structure has yet been solved for this family. As a member of clan GH-I, a lysozyme-like α-β fold is suggested, based on known GH24 and GH46 structures.

Family Firsts

First primary sequence determination

Chitosanase ChoA from Matsuebacter chitosanotabidus 3001 (now Mitsuaria chitosanitabida) [1, 8]

First stereochemistry determination

Not yet determined

First catalytic nucleophile identification

Not yet identified

First general acid/base residue identification

Not yet identified

First 3-D structure

Not yet determined

References

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2. Matsuda, Y., Iida, I., Shinogi, T., Kakutani, K., Nonomura, T., Toyoda, H. (2001) In vitro suppression of mycelial growth of Fusarium oxysporum by extracellular chitosanase of Sphingobacterium multivorum and cloning of the chitosanase gene csnSM1. J. Gen. Plant Pathol. 67, 318-324.

3. Yi, J.-H., Jang, H.-K., Lee, S.-J., Lee, K.-E., Choi, S.-G. (2004) Purification and properties of chitosanase from chitinolytic beta-Proteobacterium KNU3. J. Microbiol. Biotechnol. 14, 337-343.

7. http://www.cazy.org/Glycoside-Hydrolases.html