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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 development of urease (E.C.3.5.1.5) as a label for enzyme immunoassay (EIA) procedures is described and the use of such conjugates illustrated with examples. Urease catalyzes the hydrolysis of urea to carbon dioxide and ammonia. The production of ammonia may be detected readily by a pH shift which we have found best indicated by the vivid colour change (yellow to purple) of bromocresol purple incorporated in the substrate solution. This enzyme-substrate system offers a number of important advantages. The substrate in aqueous solution is stable, titration end points are sharp and readily visible and the enzyme is not inhibited by sodium azide. Thus, test reagents may be prepared with this preservative and stored ready to use. Urease of high specific activity is commercially available and because it does not occur in mammalian tissues, it is suitable for use in EIA tests to detect cell-associated antigens and their antibodies. Finally, the enzyme reaction may be stopped by the addition of organomercurial preservatives, thus allowing storage of developed tests for later examination.
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PMID:An investigation of the use of urease-antibody conjugates in enzyme immunoassays. 629 6

Growing steers were used in a replicated 3 X 3 Latin square to study the influence of ionophores on mineral metabolism and ruminal urease activity. Treatments consisted of: 1) basal high energy diet; 2) basal plus 33 ppm lasalocid and 3) basal plus 33 ppm monensin. Each period was 33 days and apparent absorption and retention of macrominerals were measured during the last 5 days of each period. Mineral intake during the collection period was not affected by treatment. Both ionophores increased apparent absorption of sodium, magnesium and phosphorus. Retention of magnesium and phosphorus were higher for steers receiving either lasalocid or monensin. Potassium and calcium absorption were not significantly affected by treatment. Serum concentrations of macrominerals were similar for all treatments. Zinc and copper concentrations in serum were higher in animals fed monensin or lasalocid. Steers fed either ionophore had lower concentrations of soluble potassium and calcium in rumen fluid. Both ionophores also decreased ruminal osmolality. Bacterial urease, a nickel-dependent enzyme, was decreased by 28 and 66% in animals that received lasalocid and monensin, respectively. These findings indicate that lasalocid and monensin affect metabolism of certain minerals in ruminants.
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PMID:Influence of monensin and lasalocid on mineral metabolism and ruminal urease activity in steers. 669 34

Sodium saccharin, at concentrations similar to those in the urine of rats fed 1-5% sodium saccharin in their diet, markedly inhibited urease, and 3 proteases in vitro and sodium ion did not appear to play a role in enzyme inhibition. These observations suggest that enzyme inhibition of any of a large number of enzymes may play a role in the tumorigenesis of the urinary bladder by saccharin.
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PMID:The inhibition of urease and proteases by sodium saccharin. 681 43

A mycobacterial strain known as Mycobacterial strain W was analysed for its growth characteristics and biochemical traits. This strain was found to be a rapid grower, with luxurient growth on Lowenstein-Jensen medium, Dubos agar, Middlebrook's agar and Sauton's medium. Colonies were smooth, convex and nonpigmented. Some of the colonies which appeared rough were similar to smooth colonies at least in biochemical characteristics. This organism was tolerant to wide range of temperatures and to chemical substances like thiophene - carboxylic acid hydrazide, isoniazid, sodium chloride but not to bile salts. It was negative for niacin production, for various amidases, urease production, 3 day arylsulfatase test and also for Tween 80 hydrolysis. On the other hand this strain was found to be positive for semiquantitative catalase, heat resistant catalase, nitrate reduction, sodium salicylate degradation, tellurite reduction, 14 day arylsulfatase test and fermentation of fructose. This organism could utilize sodium nitrate and sodium nitrite as sources of nitrogen but didn't exhibit any utilization of fructose, arabinose as only sources of carbon. Significance of these findings is discussed.
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PMID:A report on the biochemical analysis of Mycobacterium W. 702 33

Previous theoretical analysis has indicated that adequate mass transfer is possible in a dialyzer with reciprocating membrane motion provided that the dialysate concentration of uremic substances is kept low. Earlier models have utilized a collection of sorbents (charcoal, urease, and a cation exchanger) constrained next to the dialyzer membranes. We have designed a new dialyzer with a sorbent suspension having free access from a reservoir to the spaces between membrane packages. At a treatment rate of 150 ml/min/m2, the in vitro creatinine clearance is 75 ml/min/m2, which agrees within experimental accuracy with the theoretical prediction. The creatinine clearance, flow resistance, and compliance of the dialyzer are constant during four to six hours of testing. In vivo tests have been performed during urea and creatinine infusion in a normal dog and in a dog with 3/4 nephrectomy. The in vivo creatinine clearance agrees within 10% with the in vitro clearance. Sodium, potassium, calcium, and bicarbonate fluxes are acceptable for patients in renal failure. The new design allows a higher capacity for urea and creatinine, since larger amounts of sorbent may be used.
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PMID:A reciprocating, single-needle hemodialyzer with bidirectional flow of sorbent suspension. 718 27

Kinetic, spectral, and other studies establish that hydroxamic acids bind reversibly to active-site nickel ion in jack bean urease. Equilibrium ultracentrifugation studies establish that the molecular weight of native urease is 590 000 +/- 30 000 while that of the subunit formed in 6 M guanidinium chloride in the presence of beta-mercaptoethanol is approximately 95 000. Essentially the same subunit molecular weight (approximately 93 000) is found by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, subsequent to denaturation in a guanidinium chloride - beta-mercaptoethanol system at various temperatures. Coupled with an equivalent weight of 96 600 for binding of the inhibitors acetohydroxamic acid and phosphoramidate, these results establish securely that urease is a hexamer with one active site per 96 600-dalton subunit. Consistent values for the equivalent weight are obtained by a routine spectrophotometric titration of the active site of freshly prepared urease with trans-cinnamoylhydroxamic acid. General equations are derived which describe spectrophotometric titrations of binding sites of any enzyme with a reversible inhibitor. These equations allow the evaluation of the difference spectrum of the protein-inhibitor complex even when the binding sites cannot readily be saturated with the inhibitor or vice versa.
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PMID:Jack bean urease (EC 3.5.1.5). IV. The molecular size and the mechanism of inhibition by hydroxamic acids. Spectrophotometric titration of enzymes with reversible inhibitors. 724 34

The nitrogen excretory metabolism of the myxomycete Physarum polycephalum was studied. When cultured in partially defined broth medium or on agar, the principal excretory product was ammonia nitrogen. A small, variable quantity of urea was excreted in liquid culture. No uric acid or other purines were detected in the cultures. When microplasmodia were incubated with sodium [14C]bicarbonate, radioisotope was incorporated into citrulline, arginine, and urea. Incubation with L-[carbamoyl-14C]citrulline yielded labelled arginine, urea, and CO2. Substantial urease activity was found in extracts of the microplasmodia. These results, in conjunction with the lack of an absolute nutritional requirement for arginine, provide evidence that Physarum has a functional arginine biosynthetic pathway, an arginase, and a urease.
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PMID:Arginine synthesis and nitrogen excretion in the myxomycete Physarum polycephalum. 737 43

To investigate the mechanism of the anti-urease action of ecabet sodium (ecabet) observed in Helicobacter pylori in vitro, the effects of ecabet on purified urease from jack bean were studied in comparison with the effects of the specific urease inhibitor benzohydroxamic acid (BHA). After incubation of the enzyme with the test drug for a period of time, urease activity was measured. Ecabet depressed the activity below pH 5, and the lower the pH, the greater the degree of depression. The degree of depression by ecabet increased gradually during incubation and reached a plateau in 20 min, whereas that by BHA attained a maximum rapidly. The IC50 values of ecabet and BHA were 2.1 mg/ml and 0.5 microgram/ml, respectively. When the incubation mixture of urease with an inhibitor was diluted and further incubated, the depressed activity by BHA reverted gradually, but that by ecabet did not. When the incubation mixture of urease with ecabet was centrifuged, the urease activity of the mixture decreased in parallel with the reduction in protein concentration of the supernatant. When the incubation mixture of urease and 14C-ecabet was ultrafiltered to remove the drug, the radioactivity in the retentate remained in parallel with the degree of reduction of urease activity in the retentate. These results indicate that ecabet irreversibly depresses the urease activity of jack bean, and suggest that the depression is caused by irreversible binding of ecabet to urease followed by denaturation of the enzyme protein.
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PMID:Mechanism of anti-urease action by the anti-ulcer drug ecabet sodium. 755 Jan 19

Helicobacter pylori NCTC 11637, which is nonviable at pH 3.0, became viable after addition of 10 mM urea owing to ammonia production by urease. In a buffer supplemented with urea, ecabet sodium decreased both the production of ammonia and the number of viable cells of H. pylori NCTC 11637 and changed the bacteria from the bacilliform to the horseshoe or doughnut shape in a concentration-dependent manner. In particular, ecabet sodium (2 and 4 mg/ml) decreased the number of viable cells below the control level. Benzohydroxamic acid, a urease inhibitor, also caused a decrease in ammonia production accompanied by a decrease in the number of viable cells and changed the morphological form at pH 3.0, but the number of viable cells was not lowered below the control level. In buffers at various pHs without urea, ecabet sodium showed a concentration-dependent bactericidal effect on H. pylori at pHs 4.0 and 5.0 but not at pHs 6.0 and 7.0 while benzohydroxamic acid caused only a slight decrease in the number of viable cells at pH 4.0. These results suggest that ecabet sodium has strong bactericidal activity in addition to its urease-inhibiting activity under acidic conditions.
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PMID:Bacterial activity of a new antiulcer agent, ecabet sodium, against Helicobacter pylori under acidic conditions. 757 19

We investigated the eradication and recurrence rate of Helicobacter pylori-infected gastric ulcer patients by combination therapies. Eighty-six H. pylori-positive gastric ulcer patients were assigned randomly to one of seven groups: I, omeprazole 20 mg (n = 9); II, lansoprazole (LPZ) 30 mg (n = 16); III, LPZ 30 mg plus plaunotol 480 mg (n = 13); IV, LPZ 30 mg plus ecabet sodium 2 g (n = 11); V, LPZ 30 mg plus clarithromycin 600 mg (the first 2 weeks; n = 11); VI, LPZ 30 mg plus plaunotol 480 mg plus clarithromycin 600 mg (the first 2 weeks; n = 13); and VII, LPZ 30 mg plus ecabet sodium 2 g plus amoxicillin 1,500 mg (the first 2 weeks; n = 13). All therapy was for 8 weeks except where otherwise noted. H. pylori eradication rates as diagnosed by culture, histology, urease test, and [13C]urea breath test 4 weeks after stopping therapy were 0, 0, 8, 45, 6, 46, and 62%, respectively, in groups I-VII. No patient achieving H. pylori eradication suffered recurrence. The combination therapies with proton pump inhibitors in addition to antibiotics and antiulcer agents are safe and effective in H. pylori eradication.
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PMID:Combination therapies with a proton pump inhibitor for Helicobacter pylori-infected gastric ulcer patients. 759 30


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