Interplay of metal ions and urease

Abstract

Summary Urease, the first enzyme to be crystallized, contains a dinuclear nickel metallocenter that catalyzes the decomposition of urea to produce ammonia, a reaction of great agricultural and medical importance. Several mechanisms of urease catalysis have been proposed on the basis of enzyme crystal structures, model complexes, and computational efforts, but the precise steps in catalysis and the requirement of nickel versus other metals remain unclear. Purified bacterial urease is partially activated via incubation with carbon dioxide plus nickel ions; however, in vitro activation also has been achieved with manganese and cobalt. In vivo activation of most ureases requires accessory proteins that function as nickel metallochaperones and GTP-dependent molecular chaperones or play other roles in the maturation process. In addition, some microorganisms control their levels of urease by metal ion-dependent regulatory mechanisms.

A Bacillus paralicheniformis Iron-Containing Urease Reduces Urea Concentrations in Rice Wine

“…UreE, a metallochaperone, delivers nickel to urease apoprotein via the chaperone complex (UreD-UreF-UreG) 3 , in which UreD functions as a scaffold for the recruitment of other accessory subunits, UreF guarantees metallocenter fidelity, and UreG is a GTPase for the incorporation of nickel ions (3,4,(19)(20)(21). Although the ureD gene in Helicobacter species (18) was renamed ureH, its function is consistent with that of other UreD accessory proteins.…”

“…Although the ureD gene in Helicobacter species (18) was renamed ureH, its function is consistent with that of other UreD accessory proteins. However, in some Bacillus species, the ureD and ureH genes are both conserved (3), and the function of this heterogeneous UreH is still unclear. In addition, enzymatic elimination of urea by acid ureases has been considered to be the most efficient method of decreasing the concentration of the carcinogenic compound ethyl carbamate (EC; also known as urethane) (22)(23)(24)(25)(26) in traditional fermented foods (27)(28)(29)(30).…”

“…and H 2 N-COOH ϩ H 2 O ¡ H 2 CO 3 ϩ NH 3 ), have been found in plants and many microorganisms (1)(2)(3)(4)(5). Because of their multifaceted contributions to the environmental cycling of nitrogen and localized neutralization of pH (1,6,7), ureases have always attracted intensive attention.…”

“…To understand the activation mechanisms of ureases and the roles of accessory proteins in the posttranslational modifications of ureases, many different microbial nickel-containing ureases have been identified and characterized. Although the structural subunits and enzyme active sites have been well studied (3)(4)(5)(10)(11)(12)(13)(14)(15), the function of each accessory protein and the urease maturation mechanism are still poorly understood (3,4,(16)(17)(18)(19)(20).…”

“…In most of the microbial ureases identified, the accessory proteins (UreE, UreD, UreG, and UreF) are essential for active-site metalation and urease maturation (3,4,20). UreE, a metallochaperone, delivers nickel to urease apoprotein via the chaperone complex (UreD-UreF-UreG) 3 , in which UreD functions as a scaffold for the recruitment of other accessory subunits, UreF guarantees metallocenter fidelity, and UreG is a GTPase for the incorporation of nickel ions (3,4,(19)(20)(21).…”