Dental caries results from prolonged plaque acidification that leads to the establishment of a cariogenic microflora and demineralization of the tooth. Urease enzymes of oral bacteria hydrolyze urea to ammonia, which can neutralize plaque acids. To begin to examine the relationship between plaque ureolytic activity and the incidence of dental caries, recombinant, ureolytic strains of Streptococ...

The aim of the present work was to evaluate the influence of the lack of urease activity in some Streptococcus thermophilus strains on the primary metabolism during lactic acid fermentation. A comparison of the kinetics of the lactic acid process with the participation of ureautilizing and urease deficient streptococcal strains was performed. It was found that the lack of urease activity in the...

If the activity of an enzyme preparation is determined under conditions in which a further increase in substrate concentration is without demonstrable effect, all other factors being held constant, it is ordinarily assumed that the specific activity of the enzyme, expressed in terms of arbitrary units per unit weight of the enzyme, is independent of the absolute enzyme concentration (1, 2). How...

Morganella morganii, a very common cause of catheter-associated bacteriuria, was previously classified with the genus Proteus on the basis of urease production. M. morganii constitutively synthesizes a urease distinct from that of other uropathogens. The enzyme, purified 175-fold by passage through DEAE-Sepharose, phenyl-Sepharose, Mono-Q, and Superose 6 chromatography resins, was found to have...

A rapid, miniaturized, urea broth test useful for detecting urease activity of yeasts was compared to Christensen urea agar. All urease-producing yeasts tested were positive on both media; however, 60% were reactive in the urea R broth within 30 min, and the remainder were reactive within 4 h. This urea multiwell test may be useful as a rapid screening method for detecting urease-producing yeas...

Urease (urea amidohydrolase) is usually found in different bacteria, fungi, algae and plants. It is accountable for the hydrolysis of urea and thus, forming ammonia and carbamate, which is the final step of nitrogen metabolism in living organisms [1,2]. The carbamate intern quickly and spontaneously decomposes, yielding a second molecule of ammonia. These reactions may cause significant increas...

Proteus mirabilis, a cause of complicated urinary tract infection, produces urease, an essential virulence factor for this species. UreR, a member of the AraC/XylS family of transcriptional regulators, positively activates expression of the ure gene cluster in the presence of urea. To specifically evaluate the contribution of UreR to urease activity and virulence in the urinary tract, a ureR mu...

Nickel (Ni) is one of the essential micronutrients for higher plants and its known function is being the metal component of urease. The effects of various Ni levels on urease activity in maize (Zea maize L.) plants grown in two nutrient media containing urea or ammonium nitrate as two separate nitrogen sources were investigated. The experiments were performed as completely randomized blocks wit...

Studies with two uropathogenic urease-producing Escherichia coli strains, 1021 and 1440, indicated that the urease genes of each are distinct. Recombinant plasmids encoding urease activity from E. coli 1021 and 1440 differed in their restriction endonuclease cleavage sites and showed minimal DNA hybridization under stringent conditions. The polypeptides encoded by the DNA fragments containing t...

Fast protein liquid chromatography and SDS-PAGE have been used to isolate and purify Helicobacter pylori urease. A nickel component of the urease was detected in the purified proteins by atomic absorption spectroscopy. The nickel was present only in the 61 kDa polypeptide and in the ratio of between five and six atoms to one molecule of urease, suggesting a hexameric structure. These results ar...