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)

Concentrated broth culture supernatants from 50 to 60% of Helicobacter pylori strains induce eukaryotic cell vacuolation in vitro. A quantitative assay for cell vacuolation was developed on the basis of the rapid uptake of visibly vacuolated HeLa cells was significantly greater than that of nonvacuolated cells. By using the rapid NRU assay, we sought to determine the roles of H. pylori cytotoxin, urease, and ammonia in the vacuolation of HeLa cells. The NRU of HeLa cells incubated in medium containing ammonium chloride or ammonium sulfate was significantly greater than that of cells incubated in medium alone. In addition, ammonium salts augmented the NRU induced by H. pylori supernatants. The NRU induced by jack bean urease was augmented by the addition of urea to cell culture medium; this suggests that urease-mediated NRU occurs via the generation of ammonia. Acetohydroxamic acid blocked the NRU induced by jack bean urease and urea but failed to block the uptake induced by H. pylori supernatants. Supernatant from a non-urease-producing H. pylori mutant strain induced NRU identical to that of the urease-positive parental strain. These observations indicate that the vacuolating activity in H. pylori supernatants is not mediated solely by urease activity but that it may be potentiated by urease-mediated ammonia production.
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PMID:Effect of urease on HeLa cell vacuolation induced by Helicobacter pylori cytotoxin. 200 8

A mutant strain of Helicobacter pylori with weak urease activity was created by using N-methyl-N'-nitro-N-nitrosoguanidine. The urease activity of the mutant (0.036 +/- 0.009 nmol of urea per micrograms of bacterial protein per min) was 0.4% of that of the parental strain (8.20 +/- 2.30 nmol of urea per micrograms of bacterial protein per min). The mutant was otherwise indistinguishable from the parental strain. Both demonstrated prominent catalase and oxidase activities, and both produced vacuolating cytotoxin. Restriction endonuclease and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) patterns and ultrastructure were identical for the two strains. The mutant was fully motile, as evaluated by spreading in soft agar and by direct microscopic examination. Growth rate and colony size and morphology were identical for the mutant and parental strains. Seventeen gnotobiotic piglets were challenged with either the mutant or the parental strain and sacrificed 3 or 21 days after challenge. Gastric tissue was examined histologically and cultured for H. pylori. Of seven piglets challenged with the parental strain, all became infected. H. pylori was not recovered from any of 10 piglets challenged with the urease-negative strain. Lymphofollicular gastritis was present in all seven piglets challenged with the parental strain but in none of the piglets challenged with the urease-negative strain. These results suggest that prominent urease activity is essential for colonization by H. pylori.
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PMID:Essential role of urease in pathogenesis of gastritis induced by Helicobacter pylori in gnotobiotic piglets. 205 Apr 11

Struvite crystals were produced by Proteus mirabilis growth in artificial urine, in the presence of a number of naturally occurring crystallization inhibitors. The use of phase contrast light microscopy enabled the effects of added chondroitin sulfate A, chondroitin sulfate C, heparin sulfate, or sodium citrate, on struvite crystal growth rates to be rapidly monitored as changes in crystal habit. Struvite crystals formed as a consequence of the urease activity of P. mirabilis under all chemical conditions. In the absence of inhibitor, early crystal development was marked by large quantities of amorphous precipitate, followed immediately by the appearance of rapidly growing X-shaped or planar crystals. Addition of the glycosaminoglycans, chondroitin sulfate A, chondroitin sulfate C, or heparin sulfate to the artificial urine mixture had no effect on the rate of crystal growth or appearance. When sodium citrate was present in elevated concentrations, crystal appearance was generally slowed, and the crystals assumed an octahedral, slow growing appearance. None of the added compounds had any influence on bacterial viability, pH, or urease activity. It is therefore likely that the inhibitory activity displayed by sodium citrate might be related to its ability to complex magnesium or to interfere with the crystal structure during struvite formation. From these experiments it would appear that citrate may be a factor in the natural resistance of whole urine to struvite crystallization.
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PMID:Influence of chondroitin sulfate, heparin sulfate, and citrate on Proteus mirabilis-induced struvite crystallization in vitro. 212 9

Urease of Helicobacter pylori (formerly Campylobacter pylori) is believed to represent a critical virulence determinant for this species. Ammonia generated by hydrolysis of urea may protect the acid-sensitive bacterium as it colonizes human gastric mucosa. An H. pylori strain, cultured from a gastric biopsy of a patient with complaints of abdominal pain and a history of peptic ulcer disease, was isolated on selective medium and cultured in Mueller-Hinton broth supplemented with 4% fetal calf serum. Whole cells were ruptured by French pressure cell lysis, and soluble protein was chromatographed on DEAE-Sepharose, phenyl-Sepharose, Mono-Q, and Superose 6 resins. Purified urease represented 6% of the soluble protein of crude extract, was estimated to have a native molecular size of 550 kilodaltons (kDa), and was composed of two distinct subunits of apparent molecular sizes of 66 and 29.5 kDa. On the basis of subunit size, a 1:1 subunit ratio as measured by scanning densitometry of Coomassie blue-stained sodium dodecyl sulfate-polyacrylamide gels, and estimated native molecular size, the data are consistent with a stoichiometry of (29.5 kDa-66 kDa)6 for the structure of the native enzyme. Km for urea was estimated at 0.2 mM. By N-terminal analysis, the 29.5-kDa subunit of H. pylori urease was found to share significant amino acid sequence similarity with the smallest of three subunits of the Proteus mirabilis and Morganella morganii ureases, as well as to the amino terminus of the unique jack bean subunit. The 66-kDa subunit also shared up to 80% similarity with the largest of three subunits of P. mirabilis, M. morganii, and Klebsiella aerogenes ureases and to internal sequences (amino acids 271 to 285) of the jack bean urease subunit. Thus, the amino acid sequence is conserved among ureases with one, two, and three distinct subunits, suggesting a common ancestral urease gene. Also, urease subunits of M. morganii and jack bean were specifically recognized by antisera raised against the 66-kDa subunit of H. pylori urease, demonstrating that at least some antigenic determinants were conserved among ureases from different species.
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PMID:Purification and N-terminal analysis of urease from Helicobacter pylori. 231 39

The predominant ureolytic bacteria in the pig large intestine were determined while growing pigs were fed a basal diet or basal diet plus copper sulfate, Aureo SP250, or clinoptilolite. Fecal samples were collected from four pigs fed each diet at 3, 9, and 14 weeks and analyzed for total colony counts and percent ureolytic bacteria. Fecal urease activity, ammonia nitrogen, and identity of the ureolytic bacteria were determined at 14 weeks. Copper sulfate and Aureo SP250 reduced the number of ureolytic organisms, with a marked decrease occurring in the Streptococcus spp., which made up 74% of the ureolytic isolates from the pigs on the basal diet. Other ureolytic species detected at lower concentrations were Staphylococcus spp., Selenomonas ruminantium, Bacteroides multiacidus, and Eubacterium limosum. Copper sulfate also reduced fecal urease activity (P less than 0.10). Fecal ammonia concentrations were not different between pigs fed the various diets. These data suggest that the streptococci are the most numerous ureolytic species in the pig intestinal tract and are significantly reduced by copper sulfate and Aureo SP250; however, only copper sulfate reduced intestinal urease activity.
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PMID:Effect of dietary copper sulfate, Aureo SP250, or clinoptilolite on ureolytic bacteria found in the pig large intestine. 282 7

Campylobacter pylori infection has been associated with duodenal ulcer, gastric ulcer, and non-ulcer dyspepsia. Although in vitro studies have shown that C. pylori is susceptible to most commonly used antibiotics, predictions from in vitro sensitivity studies have not led to a safe and generally effective therapy; C. pylori has proved to be very difficult to eradicate in vivo. We used the urea breath test to assess the susceptibility of C. pylori in vivo to various drugs. C. pylori was susceptible to bismuth subsalicylate, bismuth subnitrate, and furazolidone. C. pylori was not susceptible (i.e., urease activity remained despite administration of the drug) to the following drugs: 1) antiulcer agents (cimetidine, ranitidine, famotidine, omeprazole, misoprostol, sucralfate, liquid antacids); 2) NSAIDs (aspirin, indomethacin, ibuprofen, naproxen, tolmetin); 3) antibiotics (oral penicillin V, trimethoprim-sulfamethoxazole, dicloxacillin); 4) salts (lithium, ferrous sulfate, gold); 5) miscellaneous (acetaminophen, phenytoin, hydrochlorothiazide, propranolol, metoprolol, metoclopramide, ursodeoxycholic acid). Oral antimicrobials can be administered directly onto the site of infection, so that a very low oral dose will provide many multiples of the in vitro minimal inhibitory concentration. Furazolidone suspension (7 mg) was administered seven times daily (daily dose 49 mg) to three individuals infected by C. pylori during suppression of gastric acid secretion with famotidine (40 mg bid). After 4 days, all subjects had significant reductions in urease activity (two to normal and one to a borderline value). This response suggested that very low-dose therapy may be useful either alone or combined with bismuth. Conclusive establishment of an etiologic (or major contributory) relationship of C. pylori to ulcer disease will require a safe and reliable method to eradicate the organism from the stomach and duodenum.
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PMID:In vivo susceptibility of Campylobacter pylori. 291 80

Klebsiella aerogenes urease was purified 1,070-fold with a 25% yield by a simple procedure involving DEAE-Sepharose, phenyl-Sepharose, Mono Q, and Superose 6 chromatographies. The enzyme preparation was comprised of three polypeptides with estimated Mr = 72,000, 11,000, and 9,000 in a alpha 2 beta 4 gamma 4 quaternary structure. The three components remained associated during native gel electrophoresis, Mono Q chromatography, and Superose 6 chromatography despite the presence of thiols, glycols, detergents, and varied buffer conditions. The apparent compositional complexity of K. aerogenes urease contrasts with the simple well-characterized homohexameric structure for jack bean urease (Dixon, N. E., Hinds, J. A., Fihelly, A. K., Gazzola, C., Winzor, D. J., Blakeley, R. L., and Zerner, B. (1980) Can. J. Biochem. 58, 1323-1334); however, heteromeric subunit compositions were also observed for the enzymes from Proteus mirabilis, Sporosarcina ureae, and Selemonomas ruminantium. K. aerogenes urease exhibited a Km for urea of 2.8 +/- 0.6 mM and a Vmax of 2,800 +/- 200 mumol of urea min-1 mg-1 at 37 degrees C in 25 mM N-2-hydroxyethylpiperazineN'-2-ethanesulfonic acid, 5.0 mM EDTA buffer, pH 7.75. The enzyme activity was stable in 1% sodium dodecyl sulfate, 5% Triton X-100, 1 M KCl, and over a pH range from 5 to 10.5, with maximum activity observed at pH 7.75. Two active site groups were defined by their pKa values of 6.55 and 8.85. The amino acid composition of K. aerogenes urease more closely resembled that for the enzyme from Brevibacter ammoniagenes (Nakano, H., Takenishi, S., and Watanabe, Y. (1984) Agric. Biol. Chem. 48, 1495-1502) than those for plant ureases. Atomic absorption analysis was used to establish the presence of 2.1 +/- 0.3 mol of nickel per mol of 72,000-dalton subunit in K. aerogenes urease.
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PMID:Purification and characterization of the nickel-containing multicomponent urease from Klebsiella aerogenes. 355 84

In the several strains of Ureaplasma urealyticum that we examined, all originally isolated from human sources, the ureases were found to have a pH optimum between 7.2 and 7.5, and the Km was approximately 2.5 mM urea. Using nonreducing, nondenaturing conditions for polyacrylamide gel electrophoresis, the molecular weight of the holoenzyme was determined to be approximately 380 000. Treatment with reducing agents did not affect the electrophoretic mobility and, therefore, the molecular weight of ureaplasma urease. Immunoblot analysis (using antiserum to U. urealyticum urease) after sodium dodecyl sulfate-polyacrylamide gel electrophoresis under nonreducing, denaturing conditions revealed two antigenically reactive bands of molecular weight 174 000 and 179 000. Under reducing, denaturing conditions, a single band of molecular weight approximately 179 000 was detected. Multiple forms of urease were detected by isoelectrofocusing but not by zonal electrophoresis.
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PMID:Properties of urease from Ureaplasma urealyticum: kinetics, molecular weight, and demonstration of multiple enzyme isoelectric point forms. 373 Sep 58

A method for rapid screening of isolates of pathogenic members of the family Enterobacteriaceae is described. Flow charts are used in conjunction with triple sugar iron agar, o-nitrophenyl-beta-D-galactopyranoside-phenylalanine-motility sulfate screening media, oxidase test, and six rapid biochemical tests, namely, lysine decarboxylase, urease, indole, esculin hydrolysis, malonate, and xylose. This scheme is used to provide an inexpensive but rapid presumptive identification of Salmonella, Shigella, Edwardsiella, Aeromonas, Plesiomonas, Vibrio, and Yersinia isolates from stool cultures.
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PMID:Rapid microbiochemical method for presumptive identification of gastroenteritis-associated members of the family Enterobacteriaceae. 400 22

Antigen capable of eliciting delayed hypersensitivity reactions in the skin of sensitized guinea pigs could be extracted from Cryptococcus neoformans cells by stirring the cells from 3 to 5 days in concentrated urea or guanidine. Hydrolysis of urea to ammonia by cryptococcal urease accompanied urea extraction, but alkalinity appeared neither necessary nor sufficient for extraction. Antigen from live cells gave larger delayed skin reactions than did antigen from Formalin-killed cells. Peak skin test reactivity appeared to reside in protein-rich fraction having an elution volume on Sephadex G50 corresponding to a molecular weight of 10(4). Activity precipitated with half-saturated ammonium sulfate and could be detected in a single, narrow, rapidly migrating band on disc electrophoresis. Dialyzable proteinaceous antigen and high-molecular-weight, serologically active polysaccharide were present in the antigen, but not active in the delayed hypersensitivity reactions.
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PMID:Cryptococcal skin test antigen: preparation variables and characterization. 701 33


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