Ammonia produced by ureolysis increases the gastric pH thereby providing an environment permissive for colonization of the stomach. 2 H(+) + H2O + urea = CO2 + 2 NH4(+) Optimum pH is 8.0. Active from pH 4.0 to 10.0. In unbuffered solutions, the dodecameric complex is active at pH 3.0. Nitrogen metabolism; urea degradation; CO(2) and NH(3) from urea (urease route): step 1/1. Heterohexamer of 3 UreA (alpha) and 3 UreB (beta) subunits. Four heterohexamers assemble to form a 16 nm dodecameric complex. Also associates with the outer membrane upon autolysis of neighboring bacteria. By nickel ions. Cells do not express urease. The novel dodecameric structure of the enzyme may allow it to remain active at the cell surface at acidic gastric pH. Within this dodecameric structure the 12 active sites are clustered within the interior of the proteinaceous shell. This may allow a high local concentration of ammonia within the enzyme which may protect the nickel-chelating groups from protonation. In the N-terminal section; belongs to the urease gamma subunit family. In the C-terminal section; belongs to the urease beta subunit family. The orthologous protein is known as the gamma/beta subunit (UreAB) in most other bacteria. Going unnoticed - Issue 95 of June 2008