Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:6.3.4.6 (urease)
7,490 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Struvite renal stones are caused by infection of the urine with bacteria that synthesize the enzyme urease. Ammonium is released by the breakdown of urea by urease, the urine becomes highly alkaline, and magnesium ammonium phosphate (struvite) and carbonate apatite crystallize. Incorporation of the infecting bacteria within the developing stone, results in a focus of infection that is resistant to conventional antimicrobial therapy, and which is manifested clinically by repeated urinary tract infection caused by persistent bacteriuria. Extracorporeal shock wave lithotripsy (ESWL) currently is accepted as the election treatment for most renal calculi. This trial examines the bacteriologic aspects pre and post-ESWL. Eighty adult patients, 47 females and 33 males, without clinical signs of urinary tract infections (UTI) were submitted to urine cultures pre and post-ESWL. The first 50 patients underwent during and post-ESWL, 150 blood cultures, which all proved to be negative, confirming very low risk of generalized sepsis. No patient presented fever, chills or rigors pre or postprocedures. With respect to urine cultures 43 patients (52.5%) had a pre-ESWL UTI, in comparison to 49 (60%) who had a UTI post-ESWL. The distribution of organisms pre and post-ESWL was as follows: Proteus mirabilis (22/22), Escherichia coli (11/11), Pseudomonas aeruginosa (4/5), Klebsiella pneumoniae (2/2), Enterobacter cloacae (0/1), Alcaligenes odorans (1/2) Enterococcus faecalis (1/3), Staphylococcus saprophyticus (1/2) and Candida albicans (1/1). In this study 6 patients presented bacteriuria post-ESWL probably due to bacteria from inside the calculi. According to these results, the risk of bacteremia seems to be very low. In 60% of staghorn renal stones we could demonstrate a bacterial infection.
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PMID:[Staghorn renal lithiasis treated with shock waves. Bacteriologic aspects]. 765 75

The aim of this work was to study the significance of the urease enzyme in promoting Helicobacter pylori survival in various environments. A urease-positive H. pylori isolate, strain N6, and an isogenic urease-negative strain, strain N6(ureB::TnKm), were incubated in phosphate-buffered saline at a pH ranging from 2.2 to 7.2 for 60 min at 37 degrees C in both the presence and the absence of 10 mM urea. The number of CFU per milliliter in each solution, the pH of the bacterial supernatant, and the amounts of ammonia present in the solutions were measured. H. pylori N6 survived well in solutions with pH values ranging from 4.5 to 7.0 in the absence of urea but survived in solutions only with an initial pH below 3.5 in the presence of urea. Neither strain grew after incubation in an alkaline environment. The pH of an acidic solution (i.e., 3.5) rose rapidly to 8.45 in the presence of the wild-type strain and urea. The urease-negative mutant survived in solutions with pH values ranging from 4.5 to 7.2 irrespective of the presence of urea. Ammonia was present in significant amounts when H. pylori N6 was incubated in the presence of urea. Strain N6 survived exposure to concentrations of ammonia as high as 80 mM. The acid environment of the stomach may be crucial for H. pylori survival in the presence of urea. H. pylori does not survive in the normal environment in the presence of urea because of the subsequent rise in pH rather than ammonia toxicity.
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PMID:Helicobacter pylori requires an acidic environment to survive in the presence of urea. 772 71

A membrane reactor-separator, in which an anion-exchange membrane and a urease-immobilized poly(vinyl alcohol) (PVA) membrane were clamped together to separate the feed solution and the stripping solution of a dialysis cell, was constructed. The urea in the feed solution passed through the anion-exchange membrane, water film, and then was hydrolyzed to ammonium carbamate in the urease-immobilized PVA membrane. The experimental results showed that no ammonium ion was found in the feed solution under either phosphate or citrate buffer systems at 0.05-0.2 mol dm-3 and pH 6-9, and various initial concentrations of urea in the feed solution (20-200 mmol dm-3). This indicates that the water film between two membranes allows the carbamate ions to decompose into ammonium and carbonate ions completely before entering the anion-exchange membrane. The device therefore can be used for the removal of urea from feed solution, while preventing the backflow of ammonium ions from the stripping solution or water film into feed solution. It has significant potential in the development of a wearable or portable artificial kidney. The properties of the urease-immobilized PVA membrane were examined. A kinetic model describing the transport-reaction behavior of urea in the membrane reactor-separator was developed, and the optimum values of the reactor parameters were obtained.
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PMID:Transport and hydrolysis of urea in a reactor-separator combining an anion-exchange membrane and immobilized urease. 776 2

The polymerase chain reaction was used for the detection of Helicobacter pylori from subgingival plaque in 336 periodontitis patients. A pair of primers derived from the H. pylori urease gene A served to amplify a targeted 411-bp fragment of genomic DNA. This technique permitted the detection of as few as 60 H. pylori cells. Paper point samples from 3 deep periodontal pockets per patient were immersed in 1 ml of phosphate-buffered saline or distilled water, DNA was solubilized by detergent/protease method, 3.7 microliters or 37 microliters of lysate supernatant was used as template, and the amplification product was analyzed in 1% agarose gel containing ethidium bromide. Each experiment included purified DNA and cell lysate of H. pylori as positive controls. The presence of bacteria in the sample was verified by a primer pair common to prokaryote 16S rRNA. The present study did not reveal the specific polymerase chain reaction amplification product characteristic of H. pylori. We conclude that periodontal pockets do not constitute a natural reservoir for H. pylori.
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PMID:Absence of Helicobacter pylori in subgingival samples determined by polymerase chain reaction. 780 77

An epoxy-activated continuous bed can be prepared for immobilization of proteins in a simple, rapid, and cost-effective way. The concentration of epoxy groups on the continuous bed was as high as 600 mumol/mL compressed bed (compression of the bed decreases the peak broadening). Human transferrin, human serum albumin and particularly urease were employed as model proteins. The immobilization of urease was virtually completed within 1 h in 1 M potassium phosphate, pH 7.4. The binding capacity was 97 mg of urease/mL compressed bed. This bed is of clinical interest, since it is inexpensive to prepare and permits reproducible enzymatic determination of urea in serum and urine (the chromatographic step is finished within 1-2 min).
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PMID:Continuous beds. Their applicability for immobilization of proteins. 781 19

The ability of oral immunization to interfere with the establishment of infection with Helicobacter felis was examined. Groups of Swiss Webster mice were immunized orally with 250 micrograms of Helicobacter pylori recombinant urease (rUrease) and 10 micrograms of cholera toxin (CT) adjuvant, 1 mg of H. felis sonicate antigens and CT, or phosphate-buffered saline (PBS) and CT. Oral immunization with rUrease resulted in markedly elevated serum immunoglobulin G (IgG), serum IgA, and intestinal IgA antibody responses. Challenge with live H. felis further stimulated the urease-specific intestinal IgA and serum IgG and IgA antibody levels in mice previously immunized with rUrease but activated primarily the serum IgG compartment of PBS-treated and H. felis-immunized mice. Intestinal IgA and serum IgG and IgA anti-urease antibody responses were highest in rUrease-immunized mice at the termination of the experiment. Mice immunized with rUrease were significantly protected (P < or = 0.0476) against infection when challenged with H. felis 2 or 6 weeks post-oral immunization in comparison with PBS-treated mice. Whereas H. felis-infected mice displayed multifocal gastric mucosal lymphoid follicles consisting of CD45R+ B cells surrounded by clusters of Thy1.2+ T cells, gastric tissue from rUrease-immunized mice contained few CD45R+ B cells and infrequent mucosal follicles. These observations show that oral immunization with rUrease confers protection against H. felis infection and suggest that gastric tissue may function as an effector organ of the mucosal immune system which reflects the extent of local antigenic stimulation.
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PMID:Effect of oral immunization with recombinant urease on murine Helicobacter felis gastritis. 789 Mar 80

Urease was added to urines inoculated with Escherichia coli 24 hours earlier and to control urines not inoculated with E. coli. The inoculation did not change the concentration of the measured urine components. The urease-induced ammonium ion production and pH increase was reduced in E. coli-inoculated urines compared to control urines. This suggests that E. coli can inhibit urease. The precipitation of both phosphate and magnesium on glass rods inserted in the urine was reduced with 40-50% in the E. coli-inoculated urines. The results demonstrate that E. coli can influence urease-induced crystallisation.
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PMID:Influence of Escherichia coli on urease-induced crystallisation in human urine. 835 67

To enhance the physical stability of two model proteins during solution agitation, we investigated the interaction of the nonionic surfactant poloxamer 407 (Pluronic F-127) with each protein. Vigorous agitation of aqueous solutions of interleukin-2 and urease which contained no poloxamer 407 and were maintained at 4 degrees C resulted in a greater than 50% loss in the biological activity at 12 and 24 hours, respectively. Similar aqueous solutions which were maintained at 4 degrees C and contained either urease or interleukin-2 and poloxamer 407 at a concentration of 10% w/w and 0.5% w/w, respectively lost negligible biological activity when left undisturbed for 96 hours. Moreover, when aqueous solutions of urease and interleukin-2 which contained poloxamer 407 at a concentration of 10% w/w and 0.5% w/w, respectively were maintained at 4 degrees C and subjected to agitation for 96 hours, no significant loss in the biological activity was observed for either protein. In addition, urease was observed to have increased enzymatic activity at early time points regardless of the hydrodynamic solution conditions and poloxamer 407 concentrations evaluated. In contrast, a negligible enhancement in the biological activity of interleukin-2 was observed when aqueous solutions of the protein were exposed to similar hydrodynamic conditions employed for urease solutions, but different poloxamer concentrations (0% w/w vs. 0.5% w/w). Results of molar ellipticity, [theta], versus wavelength, lambda, profiles using CD spectropolarimetry on individual aqueous solutions of both proteins containing 2% w/w poloxamer 407 were in close agreement to spectrum obtained with each protein in pH = 7 phosphate buffer (PB).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Enhanced stability of two model proteins in an agitated solution environment using poloxamer 407. 841 May 67

Reaction of Klebsiella aerogenes urease with diethylpyrocarbonate (DEP) led to a pseudo-first-order loss of enzyme activity by a reaction that exhibited saturation kinetics. The rate of urease inactivation by DEP decreased in the presence of active site ligands (urea, phosphate, and boric acid), consistent with the essential reactive residue being located proximal to the catalytic center. The pH dependence for the rate of inactivation indicated that the reactive residue possessed a pKa of 6.5, identical to that of a group that must be deprotonated for catalysis. Full activity was restored when the inactivated enzyme was treated with hydroxylamine, compatible with histidinyl or tyrosinyl reactivity. Spectrophotometric studies were consistent with DEP derivatization of 12 mol of histidine/mol of native enzyme. In the presence of active site ligands, however, approximately 4 mol of histidine/mol of protein were protected from reaction. Each protein molecule is known to possess two catalytic units; hence, we propose that urease possesses at least one essential histidine per catalytic unit.
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PMID:Diethylpyrocarbonate reactivity of Klebsiella aerogenes urease: effect of pH and active site ligands on the rate of inactivation. 842 33

Helicobacter pylori urease belongs to a family of highly conserved urea-hydrolyzing enzymes. A common feature of these enzymes is the presence of two Lewis acid nickel ions and a reactive cysteine residue in the active site. The H+/K(+)-ATPase inhibitor omeprazole is a prodrug of a sulfenamide which covalently modifies cysteine residues on the luminal side of the H+/K(+)-ATPase of gastric parietal cells. Omeprazole and eight analogues were selected based on their chemical, electronic, and kinetic properties, and each was incubated with viable H. pylori in phosphate-buffered saline at pH 7.4 for 30 min, after which 100 mM urea was added and the amount of ammonia formed analyzed after a further 10 min. Inhibition between 0% and 100% at a 0.1 mM concentration was observed for the different analogues and could be expressed as a function of the pKa-value of the pyridine, the pKa-value of the benzimidazole, the overall lipophilicity, and, most importantly, the rate of sulfenamide formation, in a quantitative structure-activity relationship. The inhibition was potentiated by a lower pH (favoring the formation of the sulfenamide) but abolished in the presence of beta-mercaptoethanol (a scavenger of the sulfenamide). Structural analogues incapable of yielding the sulfenamide did not inhibit ammonia production. Treatment of Helicobacter felis-infected mice with 230 mumol/kg flurofamide b.i.d. for 4 weeks, known to potently inhibit urease activity in vivo, as a means of eradicating the infection, was tested and compared with the effect of 125 mumol/kg omeprazole b.i.d. for 4 weeks. Neither treatment proved efficacious.
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PMID:Structure-activity relationship of omeprazole and analogues as Helicobacter pylori urease inhibitors. 852 4


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