Urease

Although the discovery of urease as the first enzyme for which nickel is essential for activity dates back to 1975, the rationale for Ni selection for the active site of this hydrolase has been only recently unraveled. The past 20 years have indeed witnessed impressive achievements in the understanding of the biological chemistry of Ni in urease, and in this chapter we aim to describe and discuss the recent advances in the comprehension of the specific role of this metal in the catalysis of urea hydrolysis. In particular, the structural features of the enzyme bound to several small molecules have shed light on the catalytic and inhibition mechanisms. The urease activation process, involving insertion of Ni into the urease active site through the action of the accessory proteins UreE, UreD, UreF, and UreG, is also dissected and analyzed.