Urease is an enzyme that catalyzes the hydrolysis of urea into carbon dioxide and ammonia. It is present in many bacteria, fungi, plants, algae, and some invertebrates. Bacterial ureases are typically cytoplasmic, consist of three subunits, with enzyme molar masses between 190 and 300 kDa. An exception is the Heliobacter urease which is composed of two subunits and along with cytoplasmic activity, has external activity in host cells. Fungal and plant ureases, such as the Jack Bean urease, are cytoplasmic and have two structural and one catalyic subunits that form trimers or hexamers. Ureases in general require nickel in the active site, are enriched with cysteines, and maintain high amino acid sequence homology across different species.