|Mucins are high-molecular-weight glycoproteins, which are heavily decorated with O-linked oligo-saccharides and n-glycan chains, linked
to a protein backbone. There are 21 mucin (MUC) genes known in the human genome. These genes encode 2 groups of mucins: secreted
mucins and membrane-bound mucins. The main mucins expressed in the stomach are MUC 1 (membrane-bound) and MUC5AC and MUC6
(secreted). MUC5AC, forming the bulk of the adherent unstirred mucous layer, is secreted by surface foveolar cells, whereas MUC6 is
secreted by neck and gland cells, and both are strongly expressed in normal gastric mucosa. These two mucin proteins remain
segregated within the mucous gel in a laminated linear arrangement. Breach of the gastric mucosa (as in the case of peptic ulcer) is
associated with quantitative or ultrastructural changes in the mucin molecule. These changes are mediated by NSAIDs, H. pylori and other
factors, and may be pre or post translational in nature.