ABSTRACT
The thick mucus layer of the gut provides a barrier to infiltration of the underlying epithelia by both the normal microbiota and enteric pathogens. Some members of the microbiota utilise mucin glycoproteins as a nutrient source, but a detailed understanding of the mechanisms used to breakdown these complex macromolecules is lacking. Here we describe the discovery and characterisation of endo-acting enzymes from prominent mucin-degrading bacteria that target the polyLacNAc structures within oligosaccharide side chains of both animal and human mucins. These O-glycanases are part of the large and diverse glycoside hydrolase 16 (GH16) family and are often lipoproteins, indicating that they are surface located and thus likely involved in the initial step in mucin breakdown. These data provide a significant advance in our knowledge of the mechanism of mucin breakdown by the normal microbiota. Furthermore, we also demonstrate the potential use of these enzymes as tools to explore changes in O-glycan structure in a number of intestinal disease states.
Subject(s)
Gastrointestinal Microbiome , Hexosaminidases/metabolism , Membrane Glycoproteins/metabolism , Mucins/metabolism , Animals , Bacteria/classification , Bacteria/enzymology , Bacteria/genetics , Bacteria/metabolism , Crystallography, X-Ray , Glycoside Hydrolases/genetics , Glycoside Hydrolases/metabolism , Hexosaminidases/chemistry , Hexosaminidases/genetics , Humans , Membrane Glycoproteins/chemistry , Molecular Structure , Mucins/chemistry , Phylogeny , Polysaccharides/chemistry , Polysaccharides/metabolism , Structure-Activity Relationship , Substrate SpecificityABSTRACT
The gel-forming properties of mucus are closely related to its functioning; although there is limited information available relating to coral mucus gels. The present study investigates coral mucus glycoprotein using rheological methods. We demonstrate the presence of a high-molecular-weight polymeric glycoprotein similar to that found in vertebrates, capable of forming a gel. The milked mucus exuded mostly from the oral cavity of corals is not a gel; however, it does show a tendency to form a gel upon concentration. Such results indicate the potential for corals to produce two different kinds of mucus, each potentially capable of performing different functions.
Subject(s)
Anthozoa/chemistry , Glycoproteins/chemistry , Mucins/chemistry , Mucus/chemistry , Animals , Anthozoa/metabolism , Electrophoresis, Polyacrylamide Gel , Gels , Glycoproteins/metabolism , Mucins/metabolism , Mucus/metabolism , RheologyABSTRACT
Otitis media with effusion (glue ear) is the most frequent cause of deafness in children. We investigated the role of gastric juice reflux in this disease. We measured pepsin concentrations in middle ear effusions from children using ELISA and enzyme activity assays. 45 (83%) of 54 effusions contained pepsin/pepsinogen at concentrations of up to 1000-fold greater than those in serum. Our data suggest that reflux of gastric juice could be a major cause of glue ear in children.
