2 H(+) + H2O + urea = CO2 + 2 NH4(+) Nitrogen metabolism; urea degradation; CO(2) and NH(3) from urea (urease route): step 1/1. Heterotrimer of UreA (gamma), UreB (beta) and UreC (alpha) subunits. Three heterotrimers associate to form the active enzyme. Belongs to the urease gamma subunit family. Neither O157 strain expresses urease due to a truncation of ureD, the last gene of the probable operon. Urease activity is restored in O157 / Sakai upon complementation with wild-type ureD. This region of the chromosome is duplicated in strain O157:H7 / EDL933 but not in O157:H7 / Sakai.