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PubMed1981

Urease inhibitor therapy in infected renal stones.

The strict dependence of struvite and carbonate apatite renal stones on the urease-producing germs confirm the need to combine bacterial urease inhibitor drugs with antibiotic treatment. Of the two antiurease drugs used the better results were obtained with acetohydroxamic acid, both for its minimum side effects and its more powerful urease-inhibitor capacity. Thus stone recurrence was avoided even in patients with urinary infection not responding to specific antibiotic treatment.

Adolescent↗

PubMed1964

TAXONOMY OF CLOSTRIDIUM BIFERMENTANS AND CLOSTRIDIUM SORDELLII. I. THEIR TOXIGENICITY, UREASE ACTIVITY, AND SPORULATING POTENCY.

Nishida, S. (Kanazawa University, Kanazawa, Japan), K. Tamai, and T. Yamagishi. Taxonomy of Clostridium bifermentans and Clostridium sordellii. I. Their toxigenicity, urease activity, and sporulating potency. J. Bacteriol. 88:1641-1646. 1964.-Strains with properties similar to those of Clostridium bifermentans were usually obtained by selecting heat-resistant substrains of C. sordellii 1734. Heat-resistant substrains obtained from seven other strains were also found to be nontoxic. Some of these heat-resistant substrains produced urease, but others did not. Substrains of typical cultures of C. sordellii thus can yield either substrains resembling nonpathogenic strains of C. sordellii culturally, or substrains resembling C. bifermentans. The sporulating potency of pathogenic and nonpathogenic strains of C. sordellii and strains of C. bifermentans proved to be significantly distinct. The sporulating potency of C. bifermentans was high, that of pathogenic strains of C. sordellii was low, and that of nonpathogenic strains of C. sordellii was intermediate between the other two.

Antitoxins↗

PubMed1963

AN ANTIBODY PRECIPITATING UREASE AND ITS POSSIBLE RELATION TO GASTRIC ULCER.

An antibody precipitating urease was found in 171 out of 180 human sera. Data obtained on limited material (50 cases) suggest that the anti-urease titre is appreciably higher in the serum of patients suffering from gastric ulcer. This is a pointer towards a possible antigen-antibody mechanism in the genesis of chronic gastric ulceration.

Animals↗

PubMed1979

Urease bound to chitin with glutaraldehyde.

The enzyme urease (urea amidohydrolase, EC 3.5.1.5) prepared from Cajanus indicus, has been immobilized with glutaraldehyde-treated chitin as the solid support. The immobilized enzyme was characterized by determining the pH profiles and optimum temperature. Effect of glutaraldehyde concentration on the binding of enzyme to chitin was studied. The storage stability of the chitin-urease system was determined.

Aldehydes↗

PubMed1979

Multilayer immobilized-enzyme filter reactors: urease bound to nylon fabric filters.

Urease was bound to commercially available nonwoven nylon fabric filters. Multilayer immobilized-enzyme filter reactors were constructed by packing varying numbers of urease-nylon filters in a column. Owing to the relatively open structure and high mechanical strength of the filter fabric, compaction and pressure drop effects were minimal. The reactors could be operated in a wide range of substrate concentrations and flow rates under conditions where mass-transfer limitations could be neglected. The kinetic behavior of the immobilized-enzyme filter reactors could be described by a linear form of the integrated Michaelis-Menten equation using a model based on the sequential action of the enzyme filters.

Acrylamides↗

PubMed1979

Hydrolysis of urea by gelatin-immobilized urease: separation of kinetic and diffusion phenomena in a model immobilized-enzyme reactor system.

Experiments and appropriate mathematical models are presented in an attempt to elucidate and separate the effects of mass transfer and immobilization on the apparent kinetics of hydrolysis of urea by urease immobilized within a crosslinked gelatin film. Diffusion of urea through the gelatin matrix appears to exert the major influence on the observed kinetics. Diffusion coefficients are measured, and a model for the "effectiveness factor" is presented, accounting for this aspect of mass transfer control. A secondary, but significant, influence on apparent kinetics arises because the reaction products lead to an increased pH level which, because of diffusion resistance, remains high within the gelatin matrix. For pH levels in the 6.7 to 9.0 range the activity of urease is a strongly decreasing function of pH. An approximate model accounting for ionic equilibrium allows this pH-diffusion effect to be introduced in such a way as to lead to predictions of the apparent kinetics that are compared with experimental observations. Examination of these results indicates that the immobilization procedure leads to some loss of activity due to an interaction of the gelatin crosslinking reaction with the enzyme itself.

Cross-Linking Reagents↗

PubMed2005

Syntheses and biological activities of chalcone and 1,5-benzothiazepine derivatives: promising new free-radical scavengers, and esterase, urease, and alpha-glucosidase inhibitors.

A series of 2,4-diaryl-2,3,4,5-tetrahydro- (36-40) and 2,4-diaryl-2,3-dihydro-1,5-benzothiazepines (25-35) have been synthesized from the corresponding chalcones 1-24. Both the benzothiazepines and chalcones were evaluated as DPPH free-radical scavengers and as inhibitors of cholinesterases, urease, and alpha-glucosidase. Compounds 2, 5, 6, 7, 10, 13, 18, 21, 36a, 37a, 37b, and 39a showed significant cholinesterase inhibiting activities. Among the 15 dihydro-1,5-benzothiazepines, 26, 32, and 35 exhibited significant radical-scavenging activities; and six tetrahydro-1,5-benzothiazepines (35, 36a, 36b, 37a, 37b, and 39a) were found to be inhibitors of AChE and BChE. Compounds 22, 25, 26, 33, 35, 36a, 37b, and 39a inhibited urease, and 25 and 27-31 were found to be potent inhibitors of alpha-glucosidase.

Butyrylcholinesterase↗

PubMed1988

Removal of urea from alcoholic beverages with an acid urease.

Urethan, a cancer causing chemical, was reported to contaminate some alcoholic beverages. Since urethan is formed by heating urea with ethyl-alcohol, removal of urea is necessary to prevent urethan formation in alcoholic beverages. Acid urease, whose optimal pH lies around 4, lowered urea concentrations in Japanese sake. This finding indicates a protective effect of acid urease on urethan's potential hazards in alcohol.

Alcoholic Beverages↗

PubMed2006

Quantum mechanical and molecular dynamics simulations of ureases and Zn beta-lactamases.

Herein we briefly review theoretical contributions that have increased our understanding of the structure and function of metallo-beta-lactamases and ureases. Both are bimetallic metalloenzymes, with the former containing two zinc ions and the latter containing two nickel ions. We describe the use of several different methodologies, including quantum chemical calculations, molecular dynamic simulations, as well as mixed QM/MM approaches and how they have impacted our understanding of the structure and function of metallo-beta-lactamases and ureases.

Binding Sites↗

PubMed1992

A study on the removal of urea from aqueous solution with immobilized urease and electrodialysis.

A five-compartment electrodialyzer with immobilized urease was developed for the removal of urea from aqueous solution. The immobilized urease, supported on polyurethane foam, was placed in the central (dilute) compartment, where urea was hydrolyzed and the products NH4+ and CO3(2-)/HCO3- were removed simultaneously by electrodialysis. The system was studied both under constant current and under constant voltage. The effects of urea concentration and applied current or voltage on the removal of urea and ammonium ions from the dilute solution were investigated. The variations of the pH of dilute solution, the current or voltage of system, and current efficiency were also examined during reaction-electrodialysis. The removal of urea by enzymic reaction was not affected significantly by the applied electric field. The current efficiencies for removing ammonium ions from dilute solution were mostly within 40-80%, and the removal percentage of ammonium ions was dependent on current density and current efficiency.

Dialysis↗

PubMed1992

A comparative study of the performance of solid supported and soluble urease for the enzymatic hydrolysis of urea.

The performance of both free and solid supported urease for the enzymatic hydrolysis of urea was studied. Kinetic analysis of reaction rate data shows that the kinetic data were consistent with the proposed model. Statistical tests validated the model. Despite the deactivation of ureases, the immobilized enzyme could be the choice for a technological process aiming at the detoxification of blood in haemoperfusion columns.

Biotechnology↗

PubMed1982

Regulation by repression of urease biosynthesis in Proteus rettgeri.

Measuring the specific enzyme activity in cells of Proteus rettgeri it was shown that urease formation is controlled by repression through ammonia. Derepressed synthesis of the enzyme, as initiated by the absence of ammonia, required an external nitrogen source, which may not only be urea, but also nitrate, glutamate or nutrient broth. In contradiction to earlier reports the observations indicated that urea is not required for the synthesis of this enzyme, and that, therefore, urease is not an inducible enzyme in this microorganism.

Culture Media↗

PubMed1993

Site-directed mutagenesis of Klebsiella aerogenes urease: identification of histidine residues that appear to function in nickel ligation, substrate binding, and catalysis.

Comparison of six urease sequences revealed the presence of 10 conserved histidine residues (H96 in the gamma subunit, H39 and H41 in beta, and H134, H136, H219, H246, H312, H320, and H321 in the alpha subunit of the Klebsiella aerogenes enzyme). Each of these residues in K. aerogenes urease was substituted with alanine by site-directed mutagenesis, and the mutant proteins were purified and characterized in order to identify essential histidine residues and assign their roles. The gamma H96A, beta H39A, beta H41A, alpha H312A, and alpha H321A mutant proteins possess activities and nickel contents similar to wild-type enzyme, suggesting that these residues are not essential for substrate binding, catalysis, or metal binding. In contrast, the alpha H134A, alpha H136A, and alpha H246A proteins exhibit no detectable activity and possess 53%, 6%, and 21% of the nickel content of wild-type enzyme. These results are consistent with alpha H134, alpha H136, and alpha H246 functioning as nickel ligands. The alpha H219A protein is active and has nickel (approximately 1.9% and approximately 80%, respectively, when compared to wild-type protein) but exhibits a very high Km value (1,100 +/- 40 mM compared to 2.3 +/- 0.2 mM for the wild-type enzyme). These results are compatible with alpha H219 having some role in facilitating substrate binding. Finally, the alpha H320A protein (Km = 8.3 +/- 0.2 mM) only displays approximately 0.003% of the wild-type enzyme activity, despite having a normal nickel content.(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗

PubMed1993

Purification and characterization of Klebsiella aerogenes UreE protein: a nickel-binding protein that functions in urease metallocenter assembly.

The Klebsiella aerogenes ureE gene product was previously shown to facilitate assembly of the urease metallocenter (Lee, M.H., et al., 1992, J. Bacteriol. 174, 4324-4330). UreE protein has now been purified and characterized. Although it behaves as a soluble protein, UreE is predicted to possess an amphipathic beta-strand and exhibits unusually tight binding to phenyl-Sepharose resin. Immunogold electron microscopic studies confirm that UreE is a cytoplasmic protein. Each dimeric UreE molecule (M(r) = 35,000) binds 6.05 + 0.25 nickel ions (Kd of 9.6 +/- 1.3 microM) with high specificity according to equilibrium dialysis measurements. The nickel site in UreE was probed by X-ray absorption and variable-temperature magnetic circular dichroism spectroscopies. The data are most consistent with the presence of Ni(II) in pseudo-octahedral geometry with 3-5 histidyl imidazole ligands. The remaining ligands are nitrogen or oxygen donors. UreE apoprotein has been crystallized and analyzed by X-ray diffraction methods. Addition of nickel ion to apoprotein crystals leads to the development of fractures, consistent with a conformational change upon binding nickel ion. We hypothesize that UreE binds intracellular nickel ion and functions as a nickel donor during metallocenter assembly into the urease apoprotein.

Amino Acid Sequence↗

PubMed2004

In vitro anti-Helicobacter pylori potential of methanol extract of Allium ascalonicum Linn. (Liliaceae) leaf: susceptibility and effect on urease activity.

The crude methanol extract of the leaf of Allium ascalonicum was screened in vitro against fi ve strains of Helicobacter pylori (Hp) (ATCC 24376, UCH 97001, UCH 97009, UCH 98026 and UCH 99039) for antibacterial activity by the agar diffusion method in Mueller-Hinton agar supplemented with de fi brinated horse blood. All the strains were inhibited by the extract to varying degrees. The minimum inhibitory concentrations (MICs) of the extract against all the tested strains ranged from 6.25 to 12.5 mg/mL. The effects of increasing concentrations of the extract on the urease activity of three of the Helicobacter pylori strains were investigated further. The results showed that increasing the concentration of the extract decreased the urease activity of all the strains tested. Phytochemical screening of the plant showed that it contains alkaloids, cardiac glycosides and saponins. The anti-Hp activity observed is discussed in relation to the chemical constituents reportedly isolated from these plants and their traditional uses. The result of this work suggests that Allium ascalonicum has some therapeutic potential against Helicobacter pylori infection, which could be explored for patients with gastroduodenal disorders.

Anti-Bacterial Agents↗

PubMed1994

Detection of alpha-urease dissociation by fluorescence emission spectroscopy.

alpha-Urease (E.C. 3.5.1.5) is a hexameric enzyme that can dissociate into two active trimers and further into six monomers (Hirai M., Kawa-Hirai, R., Hirai T., Ueki T. (1993) Eur. J. Biochem. 215, 55-61). We have attempted to detect these dissociation products using fluorescence emission and polarization spectroscopy. Our data suggest that the hexamer, the trimer and denatured monomer have fluorescence emission maximum at 330nm, 332nm, and 346nm, respectively, under our experimental conditions. We have also found that the conformation of urease subunits is only slightly modified upon dissociation to trimer, but drastically changed upon further dissociation leading to monomer.

Fluorescence Polarization↗

PubMed1990

Purification and characterization of acid urease from Lactobacillus fermentum.

Acid urease was purified to an electrophoretically homogeneous state, and the molecular weight was estimated to be 220,000. The enzyme consisted of three kinds of subunits, designated alpha, beta and gamma, with molecular weights of 67,000, 16,800 and 8600, respectively, in a (alpha 1 beta 2 gamma 1)2 structure. The isoelectric point of the enzyme was 4.8. The nickel content was found to be 1.9 atoms of nickel per alpha 1 beta 2 gamma 1 unit. The amino acid profile was different from those of known bacterial neutral ureases. The enzyme was most active at pH 2 and around 65 degrees C. It was stable between pH 3 and 9, and below 50 degrees C. The Km for urea was 2.7 mM at pH 2. The enzyme activity was inhibited by Ag+, Hg2+, Cu2+, p-chloromercuribenzoate and acetohydroxamate. The enzyme was separated into three subunits by reverse phase HPLC. The amino terminal amino acid sequences of the subunits alpha, beta and gamma were Ser-Phe-Asp-Met-, Met-Val-Pro-Gly- and Met-Arg-Leu-Thr-, respectively.

Amino Acid Sequence↗

PubMed1990

The effects of fractioned human urine on urease-induced crystallisation in vitro.

Previous studies have shown human urine to have an inhibitory action on urease-induced crystallisation. Centrifugation and 0.45 microns filtration of the urine did not reduce this activity. This eliminates larger urine particles as being the cause of the inhibitory activity. Both the retenate and the filtrate after ultrafiltration of urine with a 100.000 mol weight cut-off influenced the urease-induced crystallisation of magnesium ammonium phosphate and calcium phosphate. The results indicate that the inhibitory action is exerted by more than one urinary component.

Calcium Phosphates↗