Sialidases and Fucosidases of Akkermansia muciniphila are crucial for growth on mucin and nutrient sharing with mucus-associated gut bacteria

Abstract

The gut mucolytic specialist Akkermansia muciniphila is strongly associated with the integrity of the mucus layer. Mucin glycan utilization requires the removal of diverse protective caps, notably, fucose and sialic acid, but the enzymatic details of this process remain largely unknown. Here, we describe the specificities of ten A. muciniphila glycoside hydrolases, which collectively remove all known sialyl and fucosyl mucin caps including those with double sulphated epitopes. Structural analyses revealed an unprecedented fucosidase modular arrangement and explained the exclusive sialyl T-antigen specificity of a sialidase of a previously unknown family and catalytic apparatus. Key cell attached sialidases and fucosidases conferred mucin-binding and their inhibition abolished growth of A. muciniphila on mucin. Remarkably, the sialic acid fucose did not contribute to A. muciniphila growth, but instead promoted butyrate production by co-cultured Clostridia. This study brings unique mechanistic insight into the initiation of mucin O-glycan degradation by A. muciniphila and the nutrient sharing between key mucus-associated bacteria.

Mechanism of 2’-Fucosyllactose degradation by Human-AssociatedAkkermansia

“…Despite this genomic difference, both A. muciniphila Muc T and A. biwaensis CSUN-19 grew in 2’-FL in media lacking mucin. Furthermore, both strains significantly induced the expression of homologs of a gene encoding a GH29 fucosidase (clade 1), for which the purified protein from A. muciniphila has previously been shown to have weak activity against para-nitrophenyl-α-L-fucoside, an analog of 2’-FL (32). Interestingly, a gene unique to A. biwaensis strains encoding a different GH29 was also significantly upregulated on 2’-FL.…”

“…In our phylogenetic analysis, genes from clade 1 were significantly upregulated in both species. Interestingly, this protein in A. muciniphila Muc T , Amuc_0846, has weak activity on 2’-FL but strong mucin binding activity (32). Also in agreement, both strains downregulated (significantly only for A. biwaensis CSUN-19) another GH29 belonging to clade 7.…”

“…Although Akkermansia are predominantly mucin-degrading specialists, given the structural and compositional similarities between HMOs and mucin oligosaccharides, species may use similar enzyme to break down HMOs (26, 32). Most of the efforts in developing a mechanistic understanding of Akkermansia utilization of host glycans thus far have centered around a single isolate of A. muciniphila (Muc T ).…”

“…Most of the efforts in developing a mechanistic understanding of Akkermansia utilization of host glycans thus far have centered around a single isolate of A. muciniphila (Muc T ). The Muc T strain has been shown to use a diversity of GHs including fucosidases, β-hexosaminidases, and β-galactosidases for degrading a variety of human-glycans including HMOs and lactose (26, 32, 33). Recently, ourselves and others have identified and isolated at least four species-level phylogroups (AmI-AmIV) of human associated Akkermansia .…”

Structure and function of microbial α-l-fucosidases: a mini review

“…The capability of removing α- l -fucosyl residues from free oligosaccharides and glycoconjugates conferred fucosidase-possessing microbes a competitive advantage in mucin glycan foraging [ 14 ], and in turn help maintain intestinal homeostasis [ 76 , 77 ]. Fucosidases from commensal bacteria also play a role in cross-feeding with other members of the gut microbiota [ 78 , 79 ] or enteric pathogens such as Salmonella enterica serovar Typhimurium, Clostridium difficile , [ 80 ], Campylobacter jejuni [ 81 , 82 ] and other pathogens [ 83 ] facilitating their infection. Recently, α- l -fucosidases from the GH29 family were identified and characterised from the metagenome of faecal samples of breastfed infants.…”