Identification and characterization of a sulfoglycosidase from Bifidobacterium bifidum implicated in mucin glycan utilization

Abstract

Human gut symbiont bifidobacteria possess carbohydrate-degrading enzymes that act on the O-linked glycans of intestinal mucins to utilize those carbohydrates as carbon sources. However, our knowledge about mucin type O-glycan degradation by bifidobacteria remains fragmentary, especially regarding how they decompose sulfated glycans, which are abundantly found in mucin sugar-chains. Here, we examined the abilities of several Bifidobacterium strains to degrade a sulfated glycan substrate and identified a 6-sulfo-β-d-N-acetylglucosaminidase, also termed sulfoglycosidase, encoded by bbhII from Bifidobacterium bifidum JCM 7004. A recombinant BbhII protein showed a substrate preference toward 6-sulfated and 3,4-disulfated N-acetylglucosamines over non-sulfated and 3-sulfated N-acetylglucosamines. The purified BbhII directly released 6-sulfated N-acetylglucosamine from porcine gastric mucin and the expression of bbhII was moderately induced in the presence of mucin. This de-capping activity may promote utilization of sulfated glycans of mucin by other bacteria including bifidobacteria, thereby establishing the symbiotic relationship between human and gut microbes.

Sharing of human milk oligosaccharides degradants within bifidobacterial communities in faecal cultures supplemented with Bifidobacterium bifidum

“…Mucin is a highly glycosylated protein that is abundantly expressed in the human large intestine, and B . bifidum possesses cell wall-anchored secretory glycosidases to degrade the sugar chains 16 , 46 , 47 . Interestingly, most of the mucin-degrading glycosidases are commonly used for degradation of HMOs 16 , reflecting the similarities in the glycoside linkages between mucin glycans and HMOs.…”

Enzymatic Adaptation of Bifidobacterium bifidum to Host Glycans, Viewed from Glycoside Hydrolyases and Carbohydrate-Binding Modules

“…The reports on a GH95 1,2-α-l-fucosidase (AfcA) from B. bifidum JCM 1254 by Katayama et al [56] and a galactose operon containing a gene encoding a GH112 galacto-N-biose (GNB)/LNB phosphorylase from B. longum JCM 1217 by Kitaoka et al [57] were the key findings that revived attention on HMOs by linking them to bifidobacterial biology, long after the first notion, proposed in 1954 by Gauhe et al [58], that milk oligosaccharides serve as a bifidus factor. Since then, using the strain B. bifidum JCM 1254, extensive studies have been carried out and the gene products relevant to the HMO/mucin utilization pathways have been successfully isolated and characterized [26,27,[59][60][61][62][63][64][65][66]. These efforts have illustrated how B. bifidum extracellularly degrades HMOs and mucin O-glycans into smaller sugars by the concerted action of the many cell surface-anchored GHs summarized in Figure 1.…”

“…Additionally, sulfated Gal and GlcNAc residues are present on intestinal mucin O-glycans [72]. We have recently identified a GH20 enzyme, BbhII, as a sulfoglycosidase that can remove terminal 6-sulfated GlcNAc residues from mucin [61].…”

“…These HMO/mucin-related GHs are distributed separately within the B. bifidum genomes, rather than being clustered [25]. However, HMO/mucin supplementation induces the expression of some of these genes [25,61,82]. Although the mechanism of the transcriptional regulation remains unclear, a conserved 24 bp sequence is found upstream of these genes, which suggests the presence of a common transcriptional regulator(s) with a shared ligand(s), presumably a sugar metabolite(s) [25].…”

Utilization of Host-Derived Glycans by Intestinal Lactobacillus and Bifidobacterium Species

“…The same bifidobacterial extracellular enzymes able to trim terminal L -fucose and sialic acid residues in HMOs (α- L -fucosidases and sialidases) are responsible for the release of these molecules from mucins. A previously identified membrane-bound β- N -acetylglucosaminidase from B. bifidum , BbhII, has been recently shown to possess sulfoglycosidase activity, being able to release GlcNAc 6-sulfate, which is commonly found in O -linked glycans from mucins ( Katoh et al, 2017 ). B. bifidum is not able to use this sulfated carbohydrate but its release may contribute to the coordinated degradation of glycans by the microbial community and participate in the cross-feeding at the intestinal mucosa.…”