Glycoside Hydrolase Family 168

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• Author: Jingjing Shen
• Responsible Curator: Yaoguang Chang

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Glycoside Hydrolase Family GH168
Clan	GH-x
Mechanism	retaining
Active site residues	not known
CAZy DB link
https://www.cazy.org/GH168.html

Substrate specificities

Members of glycoside hydrolase family 168 have been shown to exhibit α-1,3-L-fucanase activity. The first member of this family, Fun168A from a marine bacterium Wenyingzhuangia funcanilytica CZ1127^T, specifically hydrolyze the α-1,3- L-fucoside bonds between 2-O-sulfated and non-sulfated fucose residues in the sulfated fucan from sea cucumber Isostichopus badionotus in a random endo-acting manner [1]. Meanwhile, five homologues of Fun168A display activities toward sulfated fucan from Isostichopus badionotus, namely WP_081987558.1, WP_068826447.1, WP_068826442.1, OHE80969.1 and WP_083194720.1.

Figure 1. The phylogenetic tree of GH168 homologues. Sequences comfirmed to exhibit α-1,3-L-fucanase activity were in red.

Kinetics and Mechanism

As mentioned in the report, Fun168A exhibited transglycosylating activity with glycerin, methanol, and L-fucose as acceptors. The transglycosylating activity of Fun168A implied its retaining mechanism in catalysis.

Catalytic Residues

Multiple sequence alignments of GH168 homologues showed that D206 and E264 in Fun168A were strictly conserved in all sequences. Two single-site mutants D206E and E264Q were established, expressed and identified in the report. These two mutants were all inactive on Ib-FUC, indicating that D206 and E264 were critical for the activity of Fun168A.

Figure 2. Multiple sequence alignments of residues in GH168 homologues. The strictly conserved residues in all sequences were indicated with black triangles.

Three-dimensional structures

No three-dimensional structure has been solved in this glycoside hydrolase family at present.

Family Firsts

First stereochemistry determination

Not yet identified.

First catalytic nucleophile identification

Not yet identified.

First general acid/base residue identification

Not yet identified.

First 3-D structure

Not yet identified.

References

1. Shen J, Chang Y, Zhang Y, Mei X, and Xue C. (2020). Discovery and Characterization of an Endo-1,3-Fucanase From Marine Bacterium Wenyingzhuangia fucanilytica: A Novel Glycoside Hydrolase Family. Front Microbiol. 2020;11:1674. DOI:10.3389/fmicb.2020.01674 |