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)

The influence of four inhibitors: boric acid, thioglycolic acid, sodium fluoride and acetohydroxamic acid on the activity of urease, both in the native form and immobilized covalently on glutaraldehyde-pretreated chitosan membrane, was studied. Urea hydrolysis was carried out in phosphate buffer, pH 7, at 25 degrees C at urea concentration of 50 mM. The immobilized urease was more resistant than the native one to the action of all the investigated inhibitors, except boric acid. This property of the enzyme offers a possibility of its practical application.
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PMID:Competitive inhibitors of free and chitosan-immobilized urease. 765 53

Proteus mirabilis urease catalyzes the hydrolysis of urea, initiating the formation of urinary stones. The enzyme is critical for kidney colonization and the development of acute pyelonephritis. Urease is induced by urea and is not controlled by the nitrogen regulatory system (ntr) or catabolite repression. Purified whole-cell RNA from induced and uninduced cultures of P. mirabilis and Escherichia coli harboring cloned urease sequences was probed with a 4.2-kb BglI fragment from within the urease operon. Autoradiographs of slot blots demonstrated 4.2- and 5.8-fold increases, respectively, in urease-specific RNA upon induction with urea. Structural and accessory genes necessary for urease activity, ureD, A, B, C, E, and F, were previously cloned and sequenced (B. D. Jones and H. L. T. Mobley, J. Bacteriol. 171:6414-6422, 1989). A 1.2-kb EcoRV-BamHI restriction fragment upstream of these sequences confers inducibility upon the operon in trans. Nucleotide sequencing of this fragment revealed a single open reading frame of 882 nucleotides, designated ureR, which is transcribed in the direction opposite that of the urease structural and accessory genes and encodes a 293-amino-acid polypeptide predicted to be 33,415 Da in size. Autoradiographs of sodium dodecyl sulfate-polyacrylamide gels of [35S]methionine-labeled polypeptides obtained by in vitro transcription-translation of the PCR fragments carrying only ureR yielded a single band with an apparent molecular size of 32 kDa. Fragments carrying an in-frame deletion within ureR synthesized a truncated product. The predicted UreR amino acid sequence contains a potential helix-turn-helix motif and an associated AraC family signature and is similar to that predicted for a number of DNA-binding proteins, including E. coli proteins that regulate acid phosphatase synthesis (AppY), porin synthesis (EnvY), and rhamnose utilization (RhaR). These data suggest that UreR governs the inducibility of P. mirabilis urease.
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PMID:Proteus mirabilis urease: transcriptional regulation by UreR. 767 44

Helicobacter pylori infection is associated with gastric mucosal damage and the infiltration of neutrophils. Myeloperoxidase from neutrophils produces hypochlorous acid, which yields monochloramine in the presence of ammonia produced by urease enzyme of Helicobacter pylori. The target cells of gastric mucosal damage are gastric mucosal cells and endothelial cells. We therefore tested the hypothesis that ammonium, hypochlorous acid, and monochloramine damage the target cells. We studied the in vitro cytotoxic effects of ammonium chloride, sodium hypochlorite, monochloramine, and activated neutrophils on the target cells. Cytotoxicity was measured by a 51Cr-release assay. Ammonium chloride, sodium hypochlorite, and monochloramine were toxic to labeled cells in a concentration dependent manner. The toxicity of these agents was in the order monochloramine > sodium hypochlorite >> ammonium chloride. Incubation of labeled cells with activated neutrophils, Helicobacter pylori, and urea resulted in cytolysis. These cytotoxicities were significantly inhibited by the scavenger of hypochlorous acid, taurine. Monochloramine is more toxic to the target cells than ammonium chloride. Although ammonium chloride at neutral pH by itself has little direct damaging effect on the gastric mucosa, it is damaging to the gastric mucosa through a reaction with hypochlorous acid, suggesting that it plays a role in Helicobacter pylori-associated gastric damage.
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PMID:Mechanism of Helicobacter pylori-associated gastric mucosal injury. 778 56

A culture isolated from an aborted fetus of a bottlenose dolphin (Tursiops truncatus) was characterized. The isolate was a gram-negative coccobacillus, and the colonial morphology was typical of a smooth Brucella. The isolate was positive for catalase, oxidase, nitrate reduction, and urease. Hydrogen sulfide was not produced. It grew in air at 37 C but required 72 hours for good growth. There was growth on media containing basic fuchsin, thionin, thionin blue, penicillin, and erythritol. The M antigen was dominant, and the isolate was lysed by 4 of 10 brucellaphages tested. The oxidative metabolic profile of the isolate was similar to that for B. abortus but differed in utilization of L-asparagine, L-glutamic acid, and DL-citrulline. Whole-cell lysates were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The protein profiles were markedly different from the protein profiles of reference strains of Brucella species. Biochemical and oxidative metabolism profiles indicated that the isolate belongs in the genus Brucella but did not match the profiles of any established species or biovars. This isolate may be an atypical strain of a recognized Brucella species or a new biovar or species of Brucella.
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PMID:Characteristics of a Brucella species from a bottlenose dolphin (Tursiops truncatus). 785 24

Inhibition of the Na+/K(+)-ATPase by a circulating endogenous digitalis- or ouabain-like substance has been associated with the pathogenesis of several forms of clinical and experimental hypertension. Inbred salt-sensitive Dahl SS/jr rats were immunized with either urease or a ouabain-urease conjugate, then challenged with a high salt diet. The salt-induced increase in blood pressure in the ouabain-urease-immunized animals was significantly less than that of the urease-inoculated rats. Sera of the ouabain-urease immunized animals cross-reacted with ouabagenin, digoxigenin, digoxin, and digitoxin, but not with aldosterone, corticosterone, deoxycorticosterone (DOC), 18-hydroxy DOC, or 19-nor DOC. The fact that hypertension was not completely blocked by immunization supports ample evidence that the disease in these animals is multifactorial with several genes involved.
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PMID:Immunization of Dahl SS/jr rats with an ouabain conjugate mitigates hypertension. 794 59

Proteus mirabilis urease, a nickel metalloenzyme, is essential for the virulence of this species in the urinary tract. Escherichia coli containing cloned structural genes ureA, ureB, and ureC and accessory genes ureD, ureE, ureF, and ureG displays urease activity when cultured in M9 minimal medium. To study the involvement of one of these accessory genes in the synthesis of active urease, deletion mutations were constructed. Cultures of a ureE deletion mutant did not produce an active urease in minimal medium. Urease activity, however, was partially restored by the addition of 5 microM NiCl2 to the medium. The predicted amino acid sequence of UreE, which concludes with seven histidine residues among the last eight C-terminal residues (His-His-His-His-Asp-His-His-His), suggested that UreE may act as a Ni2+ chelator for the urease operon. To exploit this potential metal-binding motif, we attempted to purify UreE from cytoplasmic extracts of E. coli containing cloned urease genes. Soluble protein was loaded onto a nickel-nitrilotriacetic acid column, a metal chelate resin with high affinity for polyhistidine tails, and bound protein was eluted with a 0 to 0.5 M imidazole gradient. A single polypeptide of 20-kDa apparent molecular size, as shown by sodium dodecyl sulfate-10 to 20% polyacrylamide gel electrophoresis, was eluted between 0.25 and 0.4 M imidazole. The N-terminal 10 amino acids of the eluted polypeptide exactly matched the deduced amino acid sequence of P. mirabilis UreE. The molecular size of the native protein was estimated on a Superdex 75 column to be 36 kDa, suggesting that the protein is a dimer. These data suggest that UreE is a Ni(2)+-binding protein that is necessary for synthesis of a catalytically active urease at low Ni(2+) concentrations.
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PMID:Single-step purification of Proteus mirabilis urease accessory protein UreE, a protein with a naturally occurring histidine tail, by nickel chelate affinity chromatography. 796 42

In a prospective case controlled study, we evaluated the adverse effects of long-term fluoride ingestion on the gastrointestinal tract. Ten patients with otosclerosis who were receiving sodium fluoride 30 mg/day for a period of 3-12 months, and 10 age- and sex-matched healthy volunteers were included. They were all evaluated clinically and subjected to a real time ultrasound examination, upper gastrointestinal endoscopy, and biopsies from the gastric antrum and duodenum. The biopsies were subjected to a rapid urease test as well as light and electron microscopic examinations. Ionic fluoride was estimated in the serum, urine, and drinking water using an ION 85 Ion Analyzer. Seven subjects (70%) ingesting fluoride had abdominal pain, vomiting, and nausea. Petechiae, erosions, and erythema were seen on endoscopy in all the subjects, but not in the controls. Histological examination of the gastric antral biopsy showed chronic atrophic gastritis in all the subjects but in only one (10%) healthy volunteer. Scanning electron microscopic examination showed "cracked-clay" appearance, scanty microvilli, surface abrasions, and desquamated epithelium in the subjects ingesting fluoride, but not in the controls. We conclude that long-term fluoride ingestion is associated with a high incidence of dyspeptic symptoms as well as histological and electron microscopic abnormalities.
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PMID:Toxic effects of chronic fluoride ingestion on the upper gastrointestinal tract. 803 13

The urease of Helicobacter pylori is an important antigen and appears critical for colonization and virulence. Several studies have indicated a superficial localization for the H. pylori urease, and the purpose of this study was to determine the effects of cations on the release and stability of urease activity from H. pylori cells. Incubation of partially purified H. pylori urease in water containing 1, 5, or 10 mM Ca2+, Mg2+, K+, Na+, EDTA, or EGTA [ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid] had little effect on activity. In contrast, 1 mM Fe3+, Cu2+, Co2+, or Zn2+ substantially (> 80%) inhibited activity, and 10 mM Fe2+, Mn2+, and Ni2+ inhibited about 30% of the activity. Addition of Ca2+ or Mg2+ markedly decreased extraction of urease from intact H. pylori cells by water, but 1 mM Na+, K+, EGTA, or EDTA each had minimal effects on release, suggesting that divalent cations have a role in attachment of urease to H. pylori cells. The stability of enzymatic activity at 4 degrees C was enhanced by addition of glycerol or 2-mercaptoethanol; however, even after loss of activity, full antigenicity for human serum was retained.
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PMID:Effects of cations on Helicobacter pylori urease activity, release, and stability. 826 43

Urease was purified (4126-fold) from Aspergillus niger (NRRL 003) to a homologous enzyme preparation with a specific activity of 1341 mumol min-1 (mg protein)-1. One species of urease was detected in A. niger, with Km = 3.0 mM, native molecular mass 250,000 Da, pH optimum of 8.0 and a high specificity for urea. Hydroxyurea was a strong competitive inhibitor of urease activity, while N-methylurea acted as a weak uncompetitive inhibitor, based on Lineweaver-Burk and Eadie-Hoftstee plots. The activity of urease was enhanced by, but not dependent on, the presence of Na2EDTA, DL-dithiothreitol (< or = 0.1 to 5.0 mM), Ca2+, Ba2+ and citrate (2 to 20 mM). Urease activity was not affected by Na+, K+, Cl-, Br-, acetate or nitrate (2 to 20 mM), but was significantly decreased in the presence of Li+, Ni2+, Mg2+, Zn2+ or I-. Urease activity decreased 26.0% after 30 min at 65 degrees C, and 86.5% and 100.0% after 5 and 1 min at 80 and 100 degrees C, respectively. Urease activity decreased 30.5% after 90 d at 4 degrees C and 21.0% after 28 d at -20 or -80 degrees C.
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PMID:Isolation and characterization of urease from Aspergillus niger. 833 11

We prepared a murine monoclonal antibody that recognized the Helicobacter pylori urease. Monoclonal antibody, U2, reacted with purified native urease in enzyme linked immunosorbent assay but it did not react in Western immunoblot analysis. Urease was immunoprecipitated with U2 bound to Staphylococcus aureus protein A, followed by elution and visualization by sodium dodecyl-sulfate polyacrylamide gel electrophoresis. The species and strain specificity of U2 were determined by biodot reaction with H. pylori, H. mustelae, Campylobacter spp., and other gram-negative bacteria. Monoclonal antibody, U2, was used for an indirect immunofluorescent stain of formalin fixed gastric biopsies from patients with H. pylori gastritis. The immunofluorescent stain showed spiral and coccoid forms of H. pylori within the gastric mucosa. U2 was specific for H. pylori and did not react with other tested bacteria. These findings suggest that antibody U2 might be of diagnostic value for specific immunofluorescence detection of H. pylori.
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PMID:An immunofluorescent stain for Helicobacter pylori. 835 26


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