Abstract
Sulfated fucans are important marine polysaccharides widely distributed in brown algae and echinoderms, which gained increasing research interest for their various biological and biomedical activities. Fucanases could serve as tools in the bioconversion and structural investigation of sulfated fucans. A few gene-defined endo-1,4-fucanases have been characterized, while the sequence of endo-1,3-fucanase remain unstudied. Here, an endo-1,3-fucanase gene funA was screened from the genome of marine bacterium Wenyingzhuangia fucanilytica CZ1127T using transcriptomics. None of the previously reported glycoside hydrolase domains were predicted in the enzyme FunA, which hydrolyzed sulfated fucans in a random endo-acting manner. Ultrahigh performance size exclusion chromatography-mass spectrometry and nuclear magnetic resonance analyses revealed that FunA specifically cleaves α-1,3 glycosidic linkage between 2-O-sulfated and non-sulfated fucose residues. FunA exhibited transglycosylating activity with glycerin, methanol, and L-fucose as acceptors. D206 and E264 were critical for the functioning of FunA as identified by the site-directed mutagenesis. Another five homologs of FunA were confirmed to possess endo-1,3-fucanase activities. This is the first report on the sequence of endo-1,3-fucanase. The novelty of FunA and its homologs in sequences and activity shed light on a novel glycoside hydrolase family, GH168.
Highlights
Sulfated fucans, known as fucoidans, are sulfated polysaccharides mainly composed of L-fucose and sulfate groups usually extracted from brown algae and echinoderms
Discovery of an Endo-1,3-Fucanase Gene Sequence There were significant differences in gene expression profiles when W. fucanilytica was cultured in different media (Supplementary Figure S1)
Transcriptomics and differential expression analysis revealed 441 genes up-regulated when grown on the minimal medium containing Ib-FUC compared with the minimal medium containing D-glucose
Summary
Known as fucoidans, are sulfated polysaccharides mainly composed of L-fucose and sulfate groups usually extracted from brown algae and echinoderms Because of their various biological and biomedical characteristics such as being anticoagulant (Colliec et al, 1991; Cumashi et al, 2007), antithrombotic (Min et al, 2012), anti-inflammatory (Cumashi et al, 2007), anticancer (Nagamine et al, 2020), and immunomodulatory (Amin et al, 2020), research interest in sulfated fucans have increased. According to the linkage pattern of their backbone, sulfated fucans could be generally classified into two groups (Cumashi et al, 2007): (i) type I sulfated fucans composed of homogeneous 1,3-α-Lfucopyranose residues They distributed in most of Laminariales and Ectocarpales algae (Schultz-Johansen et al, 2018), and in echinoderms including sea cucumbers (Chen et al, 2012; Yu et al, 2014a,b, 2015; Chang et al, 2016) and sea urchins (Mulloy et al, 1994; Vilela-Silva et al, 1999); (ii) type II sulfated fucans consisting of alternating 1,3- and 1,4-linked α-L-fucopyranose residues. Most of the sulfated fucans from Fucales algae adopted this linkage pattern (Jiao et al, 2011; Schultz-Johansen et al, 2018)
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