| Summary: | Urease (urea amidohydrolase, EC 3.5.1.5) is a nickel-containing enzyme produced by plants, fungi, and bacteria that catalyzes the hydrolysis of urea into ammonia and carbamate. Urease is of historical importance in Biochemistry as it was the first enzyme ever to be crystallized (1926). Finding nickel in urease’s active site (1975) was the first indication of a biological role for this metal. In this review, historical and structural features, kinetics aspects, activation of the metallocenter and inhibitors of the urea hydrolyzing activity of ureases are discussed. The review also deals with the non-enzymatic biological properties, whose discovery 40 years ago started a new chapter in the study of ureases. Well recognized as virulence factors due to the production of ammonia and alkalinization in diseases by urease-positive microorganisms, ureases have pro-inflammatory, endocytosis-inducing and neurotoxic activities that do not require ureolysis. Particularly relevant in plants, ureases exert insecticidal and fungitoxic effects. Data on the jack bean urease and on jaburetox, a recombinant urease-derived peptide, have indicated that interactions with cell membrane lipids may be the basis of the non-enzymatic biological properties of ureases. Altogether, with this review we wanted to invite the readers to take a second look at ureases, very versatile proteins that happen also to catalyze the breakdown of urea into ammonia and carbamate. Keywords: Virulence factor, Urea hydrolysis, Ureolytic microorganisms, Multifunctional proteins, Plant defense, Urease
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