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)

Small capsules of a blended chitosan (QTS)-polyvinyl alcohol (PVA) mixture were prepared by the coacervation salting-out method using sodium sulphate (20%, w/v) as a coagulation solution followed by further treatment with a solution containing formic aldehyde (7%, w/v), sulphuric acid (20%, w/v) and sodium sulphate (25%, w/v). The morphology of the microcapsule wall was observed by scanning electron microscopy (SEM). The enzyme urease, as a crude extract, was encapsulated and the cross section of the loaded capsule was observed by SEM. The enzyme extract was fully immobilized and the enzymatic assay showed the presence of the enzyme in an active form with a shift in the pH maximum activity to a lower pH.
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PMID:Preparation and scanning electronic microscopy study of chitosan/polyvinyl (alcohol)-encapsulated crude urease extract. 929 39

A modified urease hypochlorite method for measuring urea in biological fluids is described. Its novel feature is the use of 4-hydroxycoumarin as ammonia acceptor. This compound has never been used for this purpose, and it has a number of advantages over traditional phenol and its derivatives: the measurement is performed in just two steps, the compound is nontoxic and used in low concentrations, and the accuracy of measurements is higher due to decrease of the systemic error. Results of urea tests with the new kit are presented. The kit contains ready-to-use components in tablets and stabilized concentrated solutions of sodium hypochlorite and alkali. The characteristics of the kit are as follows: linearity of determination up to 25 mmoles per liter, deviation from linearity no more than 7%, and sensitivity up to 0.7 mmoles/liter.
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PMID:[A new method for urea detection in biological fluids]. 947 14

In order to clarify the mechanism of the anti-Helicobacter pylori action of ecabet sodium (ecabet), a locally acting antiulcer drug, we evaluated the effects of ecabet on H. pylori urease activity in vitro. H. pylori was cultured and a crude preparation of urease was made. Urea-dependent survival of H. pylori at acid pH was significantly inhibited by ecabet. The urease activity of intact cells and a crude enzyme preparation from H. pylori had two pH optima: pH 4.5-5.0 and 8.0. Ecabet (1-4 mg/ml) concentration dependently inhibited the urease activity of both preparations at pH 5.0, but there was no inhibition at pH 8.0. The enzyme activity was inhibited by ecabet gradually and was not restored by dilution, in contrast to the inhibition elicited by benzohydroxamic acid, a specific and reversible urease inhibitor. These results suggest that irreversible inhibition of H. pylori urease activity contributes to the anti-H. pylori action of ecabet.
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PMID:Ecabet sodium, a locally acting antiulcer drug, inhibits urease activity of Helicobacter pylori. 960 Jun 37

Helicobacter pylori exhibits chemotactic responses to urea, flurofamide, acetohydroxamic acid, and sodium bicarbonate. In buffer, the chemotactic activities of a urease-positive strain were higher than those of the isogenic urease-negative strain. Moreover, the chemotactic activities of the urease-positive strain were increased in a viscous solution containing 3% polyvinylpyrrolidone, whereas those of the urease-negative mutant were not. These results are in accordance with the fact that the mutant strain did not show swarming in motility agar regardless of having flagella. Incubation of the wild-type strain with flurofamide resulted in partial inhibition of the chemotactic activities in the viscous solution. In addition, incubation with acetohydroxamic acid, a low-molecular-weight, diffusible urease inhibitor, resulted in complete loss of chemotactic activity in the viscous solution. The inhibition of the chemotactic activity by urease inhibitors paralleled the inhibition of urease. The chemotactic activity of H. pylori was also inhibited by the proton carrier carbonyl cyanide m-chlorophenylhydrazone, showing that H. pylori utilizes proton motive force for motility. These results indicate that cytoplasmic urease plays an important role in the chemotactic motility of H. pylori under a condition that mimics the ecological niche of the bacterium, the gastric mucous layer.
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PMID:Urease plays an important role in the chemotactic motility of Helicobacter pylori in a viscous environment. 974 86

Helicobacter pylori has adapted to a very specialized niche; namely, the highly acidic, viscous, and somewhat anaerobic gastric mucus of humans. The enzyme urease is essential for colonization of the stomach, as it provides protection against gastric acidity. A spiral morphology as well as sheathed flagella have been claimed to give the bacteria an advantage in colonizing mucus. Wild type strain of H. pylori and its isogenic urease-negative mutant showed a chemotactic response to urea, flurofamide (a potent urease inhibitor), sodium ion, and bicarbonate ion. These chemotactic responses are also observed in the viscous environment. Thus, it appears that H. pylori has chemotactic movement that is independent of urease activity. The chemotactic response was inhibited by carbonyl cyanide m-chlorophenylhydrazone (CCCP), a potent H+ pump inhibitor, but not by Na+ pump-inhibiting amiloride, suggesting this response is forced by H+-driven flagellar movement. Since urea and sodium bicarbonate are secreted from the gastric epithelial surface, this chemotactic response may contribute to the colonization by H. pylori and the persistence of its infection.
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PMID:Chemotaxis of Helicobacter pylori: a urease-independent response. 984 7

Urease from seeds of the water melon was found to be inhibited by various salts of sodium. Sodium fluoride strongly inhibited the activity in the low urea concentration range. The enzyme was also inhibited by a high concentration of urea which was completely abolished in the presence of 10 mM sodium fluoride. Time-dependent inactivation of urease with iodoacetic acid, N-ethylmaleimide and p-hydroxymercuribenzoate exhibited biphasic kinetics in which half of the initial activity was lost in the fast phase and the remainder in a slow phase. Each phase exhibited first-order kinetics. These observations are suggestive of the existence of half-and-half distribution of sites.
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PMID:A study of inhibition of urease from seeds of the water melon (Citrullus vulgaris). 987 15

Three hundred thirty-three patient (116 gastric ulcer, 119 duodenal ulcer, 98 gastritis) who were successfully eradicated were enrolled in the study of H. pylori recurrence rate. H. pylori status was determined by histology, rapid urease test, 13C-urea breath test. The mean of the follow-up period was 13.3 months (2-56 months), and 15 patients showed negative to positive conversion of H. pylori. The recurrence rate was 4.4% for one year and 8.3% for two years using Kaplan-Meier analysis. Second eradication therapy after initial failure is another concern. Nineteen patients were assigned to receive an 1-week new triple therapy (clarithromycin, metronidazole and PPI), in whom a 2-week course of dual therapy (amoxicillin plus PPI) failed (group1). Another 15 patients in whom the 1-week new triple therapy failed were switched to the 2-week course of dual therapy plus ecabet sodium (group2). H. pylori was eradicated in 84.2% (16/19) of patients in group1 and 86.7% (13/15) in group2.
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PMID:[Recurrence rate of H. pylori after successful eradication and second eradication therapy after initial failure of treatment]. 1003 47

We have previously characterized an exocellular serine-thiol proteinase activity in Paracoccidioides brasiliensis, using as substrates peptides analogous of the internally quenched fluorogenic peptide Abz-MKRLTL-EDDnp. In this communication, detection of maximal proteinase activity in the culture supernatant fluids followed the abrupt increase in the medium pH, owing to the accumulation of ammonia generated by urease activity. Culture supernatant fluids collected at the peak of proteinase activity against Abz-MRKLTL-EDDnp were able to cleave components of the basal membrane of the extracellular matrix (EM), including laminin, fibronectin, collagen type IV and proteoglycans, and the proteolytic activity was selectively inhibited both by PMSF and p-HMB (sodium 7-hydroxymercuribenzoate), which are also specific inhibitors of the serine-thiol proteinase. Human collagen I, bovine fibrinogen, human immunoglobulin G, BSA or P. brasiliensis gp43 were resistant to proteolysis. The kinetics of appearance of the proteinase activity against EM substrates coincided with that of proteolysis of Abz-MKRLTL-EDDnp. Moreover, chromatographic fractions of culture supernatants containing the serine-thiol proteinase at high specific activity were also active against EM substrates. These data suggest the involvement of this enzyme activity in the degradation of the basement membrane, which is the first step for fungal tissue invasion.
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PMID:Exocellular proteolytic activity of Paracoccidioides brasiliensis: cleavage of components associated with the basement membrane. 1007 6

It has been shown that urea in fermented beverages and foods can serve as a precursor of ethylcarbamate, a potential carcinogen, and acid urease is an effective agent for removing urea in such products. We describe herein the purification and characterization of a novel acid urease from Arthrobacter mobilis SAM 0752 and show its unique application for the removal of urea from fermented beverages using the Japanese rice wine, sake, as an example. The purified acid urease showed an optimum pH for activity at pH 4.2. The enzyme exhibited an apparent K(m) for urea of 3.0 mM and a Vmax of 2370 mumol of urea per mg and min at 37 degrees C and pH 4.2. Gel permeation chromatographic and sodium dodecyl sulfate gel electrophoretic analyses showed that the enzyme has an apparent native molecular weight (M(r)) of 290,000 and consisted of three types of subunit proteins (M(r), 67,000, 16,600, 14,100) denoted by alpha, beta, and gamma. The most probable stoichiometry of the subunits was estimated to be alpha: beta: gamma = 1:1:1, suggesting the enzyme subunit structure of (alpha beta gamma)3. The enzyme also existed as an aggregated form with an M(r) of 580,000. The purified enzyme contained 2 g-atom of nickel per alpha beta gamma unit of the enzyme. Enzyme activity was inhibited by acetohydroxamic acid, HgCl2, and CuCl2. The isoelectric point of the native enzyme was estimated by gel electrofocusing to be 6.8. Urea (50 ppm), which was exogenously added to sake (pH 4.4, 17 +/- 1% (v/v) ethanol), was completely decomposed by incubation with the enzyme (0.09 U ml-1) at 15 degrees C for 13 days. The enzyme was unstable at temperatures higher than 65 degrees C and pHs lower than 4, and was completely inactivated under the conditions of a pasteurization step involved in the traditional sake-making processes. These results indicate that the enzyme is applicable to the elimination of urea in fermented beverages with minimal modification to the conventional process.
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PMID:Purification, characterization, and application of an acid urease from Arthrobacter mobilis. 1019 59

Helicobacter pylori colonizes the human gastric mucosa and produces large amounts of urease. The enzyme was extracted from the bacteria by distilled water and purified by gel-permeation (Sephacryl S-300), anion-exchange chromatography (Mono Q) and a second gel-permeation (Superdex 200). Urease enzyme activity was detected with a spectrophotometic assay based on phenol red. The optimal pH for anion-exchange was 6.9. The recovery of urease was 55-75%, purity 93-98% and the overall protein recovery 0.8-1.4%. The urease in the final extract still had enzymatic activity and showed the typical subunits of Mr 66000 and Mr 30000 when subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis.
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PMID:Purification of surface-associated urease from Helicobacter pylori. 1068 Oct 57


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