Some adhesins and receptors are noted in Table 1 as adapted from Moran. There has been some evidence of tissue tropism in H. pylori colonization. The patterns of tropism are not yet understood, but the classification of adhesins and receptors could lead to an explanation. The enzyme urease plays a role in the bacterium's ability to colonize the acidic gastric environment. The enzyme is found readily on the surface and in the cytoplasm of the bacterium.
Urease helps digest urea to produce ammonia and bicarbonate.
Ammonia generated around the bacterial cells neutralizes gastric acid. This process benefits the bacterium, but is toxic to gastric epithelial cells. Pathogenicity Ammonia production from urease activity is toxic to mammalian cells. Epithelial cells undergo vacuolation because of urease activity. In addition, urease and other products of H. pylori , including protease, catalase, and phospholipases A2 and C, cause weakening of the mucous bicarbonate layer of the GI tract and damage to surface epithelial cells.