<p>Urease <db_xref db="EC" dbkey="3.5.1.5"/> is a nickel-binding enzyme that catalyzes the hydrolysis of urea to carbon dioxideand ammonia [<cite idref="PUB00001363"/>]:<reaction>Urea + H₂O = CO₂ + 2 NH₃ </reaction>Historically, it was the first enzyme to be crystallized (in 1926). It is mainlyfound in plantseeds and microorganisms. In plants, urease is a hexamer of identical chains. In bacteria[<cite idref="PUB00003605"/>], it consists of either two or three different subunits (alpha <db_xref db="INTERPRO" dbkey="IPR005847"/>, beta <db_xref db="INTERPRO" dbkey="IPR002019"/> and gamma, described in this entry). The structure of theurease complex is known [<cite idref="PUB00005206"/>].</p>This subunit does not appear to take part in the catalytic mechanism. Urease, alpha/gamma subunit