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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.
