urease

Urease is a nickel-containing metalloenzyme that catalyzes the hydrolysis of urea to carbon dioxide and ammonia. The chemical reaction is: urea + water → CO2 + 2 NH3. The enzyme is widespread and found in bacteria, plants, fungi, and some archaea. In bacteria, notable producers include Helicobacter pylori, Proteus species, and Klebsiella, where urease can contribute to virulence, urinary tract infections, and nitrogen cycling in soils and animal waste.

The catalytic active site contains two nickel ions essential for activity, coordinated by histidine and other ligands, with a post-translational carbamylated lysine involved in nickel binding. The mechanism involves activation of a water molecule by the nickel center, generating a nucleophilic hydroxide that attacks the carbonyl carbon of urea, releasing ammonia and carbon dioxide.

Physiological and ecological roles vary by organism. In soil and agricultural contexts, urease rapidly converts applied urea fertilizers into ammonia, influencing nitrogen availability and fertilizer efficiency; this can also lead to ammonia volatilization if not managed. In pathogens such as H. pylori, urease helps neutralize stomach acid, aiding survival in acidic environments and contributing to pathogenicity.

Applications and inhibition: urease activity is used in diagnostic tests for infections (such as rapid urease tests for H. pylori) and in research to study nitrogen metabolism. Urease inhibitors (including acetohydroxamic acid and various borates or amide derivatives) are employed to control ammonia release in agricultural settings and to study enzyme mechanisms. Structurally, urease commonly forms multimeric assemblies (for example, dodecameric arrangements) composed of multiple subunit types, reflecting its conserved but adaptable nature across taxa.