Unique adaptations in sulfatases underpin colonic mucin degradation by Akkermansia muciniphila

Abstract

Excessive foraging of colonic mucin glycans by gut bacteria is associated with diseases such as inflammatory bowel disease. Although Akkermansia muciniphila is an important mucin degrader, the role of carbohydrate sulfatases that facilitate digestion of these heavily sulfated glycans remains unclear. Combining in vitro digestion assays, proteomics and structural biology, we show that A. muciniphila sulfatases, such as Amuc1755 and Amuc0953, have rare adaptations targeted towards known sulfated mucin structures. They show larger degrees of modularity, including a previously unknown mucin-binding domain. When grown on colonic mucin substrates, glycoproteins of reduced size were important for the growth of A. muciniphila. Further mutational analysis and localization studies revealed that desulfation of N-acetyl-d-glucosamine was periplasmic, while desulfation of d-galactose occurred extracellularly and in the periplasm. These data improve our understanding of contexts for the positive health correlations of A. muciniphila while metabolizing colonic mucin as its sole carbon source. Structural and biochemical follow-up of a serendipitous discovery reveals that Akkermansia muciniphila carbohydrate sulfatases are uniquely adapted to digest colonic mucins in collaboration with other members of gut microbiota.