2 H(+) + H2O + urea = CO2 + 2 NH4(+) Binds 2 nickel ions per subunit. 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. Carboxylation allows a single lysine to coordinate two nickel ions. Belongs to the metallo-dependent hydrolases superfamily. Urease alpha subunit family. The orthologous protein is known as the alpha subunit (UreC) in most other bacteria.