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)

In developing countries such as Ethiopia, where chronic gastritis and peptic-ulcer disease are the most common endoscopic findings, it is important to study the association between Helicobacter pylori infection and gastroduodenal diseases. Both invasive and non-invasive diagnostic methods were therefore used to investigate 300, consecutive, adult patients with dyspepsia, from the gastrointestinal clinic of Tikur Anbassa University Hospital, Addis Ababa. The apparent overall prevalence of H. pylori infection varied according to the detection method employed. Culture revealed H. pylori in only 69% of the patients but this pathogen appeared more common when rapid urease tests (71%), PCR-denaturating gradient gel electrophoresis (91%), histopathology (81%), silver staining (75%) or stool-antigen tests (81%) were employed. Antibodies to H. pylori were detected, both by enzyme immuno-assay (EIA) and immunoblotting, in approximately 80% of the patients, whether the antigens used were of a reference strain or from a local isolate of H. pylori. When some of the EIA-positive and EIA-negative sera were cross-absorbed with antigens of Campylobacter jejuni and re-tested by EIA, the H. pylori-positive sera remained positive and the negative sera remained negative. Dyspeptic patients in Ethiopia, like most of those previously observed elsewhere in Africa, are often infected with H. pylori. It is important that the management of these patients should not be hampered by the misinterpretation of the African epidemiology of this pathogen.
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PMID:Prevalence of Helicobacter pylori infection among adult dyspeptic patients in Ethiopia. 1503 28

We describe a technique whereby intracellular urease activity can be localized by transmission electron microscopy. The ammonia produced from the enzymatic hydrolysis of urea is first precipitated with sodium tetraphenylboron and then replaced with silver to produce electron-dense silver tetraphenylboron. This direct reaction product deposition procedure was used to demonstrate the presence of membrane-bound urease of Staphylococcus sp. H3-22, a gram-positive ruminal bacterium.
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PMID:Cytochemical Localization of Urease in a Rumen Staphylococcus sp. by Electron Microscopy. 1634 4

The method of recovering Helicobacter pylori DNA or viable cells absorbed on a string that a person has swallowed and that is retrieved an hour later (string test) should be a useful alternative to traditional analysis of cells or DNA obtained by endoscopy, which is invasive, uncomfortable, relatively costly, and ill-suited for community-based and pediatric studies. Here we assayed the sensitivity and validity of the string test versus conventional endoscopic biopsy for detecting and analyzing H. pylori infection. Forty-four people with gastric complaints were studied using both H. pylori culture and urease gene (ureB) PCR. H. pylori organisms cultured from strings and biopsy specimens from the same patients were fingerprinted by the randomly amplified polymorphic DNA (RAPD) method. Biopsy sections were also hematoxylin and eosin and silver stained for H. pylori detection. H. pylori was cultured from 80% of strings and detected by PCR from 91% of strings from participants whose biopsies had been H. pylori positive by culture, PCR, and/or histology. Strains recovered from strings and biopsy specimens yielded identical or closely related RAPD profiles in each of the 24 cases tested. We conclude that the string test is a useful method for H. pylori recovery and analysis when relatively noninvasive procedures are needed.
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PMID:Validation of string test for diagnosis of Helicobacter pylori infections. 1651 86

A 74-year-old woman presented with painful ulcerative nodules on the left forearm. She had received systemic steroid therapy for rheumatoid arthritis for several years. On physical examination, there were four hemorrhagic ulcerative nodules with a linear distribution on the left forearm (Fig. 1A). These nodules had developed over the course of 2 months, and the number of lesions had increased despite systemic antibiotic therapy. There was no sign of systemic dissemination of the disease. Biopsy of a nodule demonstrated suppurative granulomatous infiltration (Fig. 1B); the hyphae stained positive with periodic acid-Schiff (data is not shown) and Gomori-methenamine silver stains in the dermis (Fig. 1C). The biopsy specimen was cultured in Sabouraud's dextrose agar supplemented with cycloheximide with incubation at 26 degrees C. A yeast-like creamy colony grew in 1 week. The colony became yellowish gray in color and the surface folded radially after 4 weeks of incubation (Fig. 2A). Microscopic examination revealed arthroconidia and blastoconidia (Fig. 2B), and urease activity was positive. The fungus was identified as Trichosporon beigelii by yeast biochemical card (YBC, Biomerieux Vitek, Inc., Hazelwood, MO, USA). The sequences of rDNA obtained from the colony were amplified using polymerase chain reaction (PCR) primer, analyzing the sequences of the 5.8S and 28S rDNA regions for the genetic identification of the Trichosporon species. The sequences of the PCR product matched the corresponding sequences of the T. inkin strain with 99% accuracy (Fig. 2C). The patient was given oral itraconazole for 8 weeks with good clinical results.
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PMID:Trichosporon inkin subcutaneous infection in a rheumatoid arthritis patient. 1734 85

The care of many patients undergoing long-term bladder catheterisation is complicated when the flow of urine through the catheter is blocked by encrustation. The problem results from infection by urease-producing bacteria, especially Proteus mirabilis, and the subsequent formation of crystalline biofilms on the catheter. The aim of this study was to discover how P. mirabilis initiates the development of these crystalline biofilms. The early stages in the formation of the biofilms were observed on a range of Foley catheters in a laboratory model of the catheterised bladder. Scanning electron micrographs revealed that when all-silicone, silicone-coated latex, hydrogel-coated latex, hydrogel/silver-coated latex and nitrofurazone silicone catheters were inserted into bladder models containing P. mirabilis and alkaline urine, their surfaces were rapidly coated with a microcrystalline foundation layer. X-ray microanalysis showed that this material was composed of calcium phosphate. Bacterial colonisation of the foundation layer followed and by 18h the catheters were encrusted by densely populated crystalline P. mirabilis biofilms. These observations have important implications for the development of encrustation-resistant catheters. In the case of silver catheters for example, bacterial cells can attach to the crystalline foundation layer and continue to grow, protected from contact with the underlying silver. If antimicrobials are to be incorporated into catheters to prevent encrustation, it is important that they diffuse into the urine and prevent the rise in pH that triggers crystal formation.
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PMID:Observations on the development of the crystalline bacterial biofilms that encrust and block Foley catheters. 1855 Feb 19

The inhibition of urease by heavy metal ions has been habitually ascribed to the reaction of the ions with enzyme thiol groups, resulting in the formation of mercaptides. To probe the modes of metal binding to the enzyme, in this work the reaction of mono- (Ag, Hg) and di- (Cu, Hg) valent metal ions with jack bean urease was studied. The enzyme was reacted with different concentrations of the metal ions for different periods of times, when its residual activity was assayed and thiol content titrated. The titration carried out with DTNB was done to examine the involvement of urease thiol groups in metal ion binding. The binding was further probed by reactivation of the metal ion-enzyme complexes with DTT, EDTA and dilution. The results are discussed in terms of the HSAB concept. In inhibiting urease the metal ions showed a common feature in that they inhibited the enzyme within a comparable micromolar range, and also in that their inhibition was multisite. By contrast, the main distinguishing feature in their action consisted of the involvement of enzyme thiol groups in the reaction. Hg (2+) and Hg2(2+) inhibition was found thoroughly governed by the reaction with the enzyme thiols, and the complete loss of enzyme activity involved all thiols available in the enzyme under non-denaturating conditions. In contrast, Ag+ and Cu2+ ions for the complete inactivation of the enzyme required 53 and 60% of thiols, respectively. Accordingly, Ag+ and Cu2+ binding to functional groups in urease other than thiols, i.e. N- and O-containing groups, cannot be excluded. Based on the reactivation experiments this seems particularly likely for Cu2+, whose concurrent binding to thiols and other groups might distort the architecture of the active site (the mechanism of which remains to be elucidated) resulting in the observed inhibitory effects.
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PMID:Mono- (Ag, Hg) and di- (Cu, Hg) valent metal ions effects on the activity of jack bean urease. Probing the modes of metal binding to the enzyme. 1860 77

The potential of employment of free as well as alginate-immobilized urease for the quantitation of cadmium (Cd(2+)) was explored. Urease from the seeds of pumpkin (Cucumis melo) was purified to apparent homogeneity by heat treatment at 48 +/- 0.1 degrees C and gel filtration through Sephadex G-200. The purified enzyme exhibited a single band on native PAGE under coomassie brilliant blue and silver staining. The enzyme entrapped in 3.5% alginate beads (with 86% immobilization) exhibited no leaching over a period of 15 days at 4 degrees C. Urease-catalyzed urea hydrolysis by both soluble and immobilized enzyme revealed a dependence on the inhibitor concentration. The inhibition caused by Cd(2+) was non-competitive and the interaction of Cd(2+) with the enzyme was irreversible as the activity could not be restored by dialysis. The time-dependent inhibition both in the presence and in absence of substrate revealed a biphasic inhibition of the activity. The significance of the results is discussed.
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PMID:Employment of pumpkin (Cucumis melo) urease entrapped in alginate beads for quantitation of cadmium in aqueous media. 1883 Aug 81

The aim of this study was to examine the structure of the crystalline bacterial biofilms that encrust and block silver/hydrogel-coated latex catheters. Scanning electron microscopy was used to examine the crystalline deposits that were found encrusting catheters obtained from six patients undergoing long-term catheterization in a community setting. Large populations of bacilli and cocci were seen on all catheters developing on a basal foundation layer of crystalline material. These observations show that in patients prone to catheter encrustation, crystalline material formed in the urine can cover the surfaces of silver catheters. Extensive bacterial biofilms then develop on the crystals, shielded from the underlying silver. It is suggested that if antimicrobials are to be incorporated into catheters to prevent encrustation, they must diffuse out from the catheter surface and reduce the viable cell populations of the urease producing bacteria that elevate the urinary pH and trigger crystal formation.
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PMID:A study of the structure of the crystalline bacterial biofilms that can encrust and block silver Foley catheters. 1918 89

We show a simple strategy to obtain an efficient enzymatic bioelectrochemical device, in which urease was immobilized on electroactive nanostructured membranes (ENMs) made with polyaniline and silver nanoparticles (AgNP) stabilized in polyvinyl alcohol (PAni/PVA-AgNP). Fabrication of the modified electrodes comprised the chemical deposition of polyaniline followed by drop-coating of PVA-AgNP and urease, resulting in a final ITO/PAni/PVA-AgNP/urease electrode configuration. For comparison, the electrochemical performance of ITO/PAni/urease electrodes (without Ag nanoparticles) was also studied. The performance of the modified electrodes toward urea hydrolysis was investigated via amperometric measurements, revealing a fast increase in cathodic current with a well-defined peak upon addition of urea to the electrolytic solution. The cathodic currents for the ITO/PAni/PVA-AgNP/urease electrodes were significantly higher than for the ITO/PAni/urease electrodes. The friendly environment provided by the ITO/PAni/PVA-AgNP electrode to the immobilized enzyme promoted efficient catalytic conversion of urea into ammonium and bicarbonate ions. Using the Michaelis-Menten kinetics equation, a K(M)(app) of 2.7 mmol L(-1) was obtained, indicating that the electrode architecture employed may be advantageous for fabrication of enzymatic devices with improved biocatalytic properties.
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PMID:Enzyme immobilization on Ag nanoparticles/polyaniline nanocomposites. 1942 91

Various inhibitors were tested for their inhibitory effects on soybean urease. The K(i) values for boric acid, 4-bromophenylboronic acid, butylboronic acid, and phenylboronic acid were 0.20 +/- 0.05 mM, 0.22 +/- 0.04 mM, 1.50 +/- 0.10 mM, and 2.00 +/- 0.11 mM, respectively. The inhibition was competitive type with boric acid and boronic acids. Heavy metal ions including Ag(+), Hg(2+), and Cu(2+) showed strong inhibition on soybean urease, with the silver ion being a potent inhibitor (IC(50) = 2.3 x 10(-8) mM). Time-dependent inhibition studies exhibited biphasic kinetics with all heavy metal ions. Furthermore, inhibition studies with sodium salts of mineral acids (NaF, NaCl, NaNO(3), and Na(2)SO(4)) showed that only F(-) inhibited soybean urease significantly (IC(50) = 2.9 mM). Competitive type of inhibition was observed for this anion with a K(i) value of 1.30 mM.
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PMID:Inhibition studies of soybean (Glycine max) urease with heavy metals, sodium salts of mineral acids, boric acid, and boronic acids. 2001 94


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