[Role of glycoproteins in the pathogenesis of peptic ulcer]

Glycoproteins are major constituents of the two-component mucous barrier: glycoproteins of the mucin-type rich in carbohydrate groups form the viscoelastic mucous gel of the mucosa, oligosaccharides of glycoproteins and glycosphingolipids embedded into the plasma membrane form the glycocalyx of the epithelial cell surface. Both structures are thought to play major roles in protecting gastric mucosa against luminal acid and proteases. This assumption is supported by experimental evidence for mucus glycoproteins, however is largely hypothetical for cell surface glycoproteins. Reports that biosynthesis of mucus glycoproteins is decreased during gastric ulceration, while breakdown is enhanced indicate that disorders of glycoprotein biosynthesis and degradation may contribute to the pathogenesis of peptic ulcer disease. The molecular mechanisms responsible for the observed alterations, however, are unknown. Possible alterations of glycoprotein metabolism that may occur at different stages of biosynthesis and degradation are discussed.