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Glycoside Hydrolase Family 168

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Glycoside Hydrolase Family GH168
Clan GH-x
Mechanism retaining
Active site residues not known
CAZy DB link

Substrate specificities

Members of GH168 have been shown to exhibit α-1,3-L-fucanase activity. The first member of this family, Fun168A from a marine bacterium Wenyingzhuangia funcanilytica CZ1127T, specifically hydrolyzes 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. Meanwhile, five homologues of Fun168A display activities toward sulfated fucan from Isostichopus badionotus [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

W. funcanilytica Fun168A exhibited transglycosylating activity with glycerin, methanol, and L-fucose as acceptors. This transglycosylating activity implied a retaining mechanism of catalysis [1].

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 of W. funcanilytica Fun168A, D206E and E264Q, were inactive on Ib-FUC, indicating that D206 and E264 were critical for activity [1].

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

Three-dimensional structures

No three-dimensional structure has been solved in this 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.


  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 | PubMed ID:32849348 [Shen2020]