Biochemical characterization and cleavage specificities analyses of three endo-1,3-fucanases within glycoside hydrolase family 174

Sulfated fucans have garnered extensive research interest in recent decades due to their varied bioactivity. Fucanases are important tools for investigating sulfated fucans. This study reported the bioinformatic analysis and biochemical properties of three GH174 family endo-1,3-fucanases. Wherein, Fun174Rm and Fun174Sb showed the highest optimal reaction temperature among the reported fucanases, and Fun174Sb possessed favorable thermostability and catalysis efficiency. Fun174Rm displayed a random endo-acting manner, while Fun174Ri and Fun174Sb hydrolyzed sulfated fucan in processive manners. UPLC-MS and NMR analyses confirmed that the three enzymes catalyze cleavage of the α(1 → 3)-bonds between Fucp2S and Fucp2S in the sulfated fucan from Isostichopus badionotus. These enzymes demonstrated novel cleavage specificities, which could accept α-Fucp2S residues at subsites -1 and + 1. The acquiring of these biotechnological tools would be beneficial to the in-depth research of sulfated fucans.

Characterization of an endo-1,3-fucanase from marine bacterium Wenyingzhuangia aestuarii: The first member of a novel glycoside hydrolase family GH174

Sulfated fucans are important marine polysaccharides with various biological and biomedical activities. Fucanases are favorable tools to establish the structure-activity relationships of sulfated fucans. Herein, gene fun174A was discovered from the genome of marine bacterium Wenyingzhuangia aestuarii OF219, and none of the pre-defined glycosidic hydrolase domains were predicted in the protein sequence of Fun174A. Recombinant Fun174A demonstrated a low optimal reaction pH at 5.5. It might degrade sulfated fucans in an endo-processive manner. Glycomics and NMR analyses proved that it specifically hydrolyzed α-1,3-l-fucoside bonds between 2-O-sulfated and non-sulfated fucose residues in the sulfated fucan from sea cucumber Isostichopus badionotus. D119, E120 and E218 were critical for the activity of Fun174A, as identified by site-directed mutagenesis. Three homologs of Fun174A were confirmed to exhibit endo-1,3-fucanase activities. The novelty on sequences of Fun174A and its homologs reveals a new glycoside hydrolase family, GH174.