Plant ureases: Roles and regulation

Both urea and urease were subjects of early scientific investigations. Urea was the first organic molecule to be synthesized and jack bean urease was the first enzyme ever to be crystallized. About 50 years later it was shown to be the first nickel metalloenzyme. Since then, nickel-dependent ureases have been isolated from many bacteria, fungi and higher plants. They have similar structures and mechanisms of catalysis. A urease apoenzyme needs to be activated. This process requires participation of several accessory pro teins that incorporate nickel into the urease forming catalytic site. In th is review, ureases from various organisms are briefly described and the sim ilarities of their structures discussed. Moreover, the significance of urea recycling in plants is explained and recent literature data about the func tion and activation of plant ureases are presented.