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)

Tests were conducted to determine the effects of Profenfos [(0-(4-bromo-2-chlorophenyl) 0-ethyl S-n-propyl-phosphorothioat] on fungal populations and some activities in soil. Profenfos (at 5.4 micrograms active ingredient/g dry soil), has a significant adverse effect on the count of total fungi after 2, 4 and 6 weeks after treatment. This effect was completely alleviated after longer incubation. Incorporation of this insecticide into the agar medium inhibited the total count of soil fungi at 6.4 and 38.4 micrograms ml-1. Initial activation followed by a decrease in CO2 output occurred in soil treated with 5.4 micrograms a.i./g. The two doses of Profenfos accelerated urease activity for 6 weeks after soil treatment, but inhibited the enzyme activity after longer periods. An inhibitory effect on nitrate reductase activity was observed with some insecticide treatments in the early stages of incubation followed by an activation in certain cases.
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PMID:Effect of soil treatment with the organophosphorus insecticide Profenfos on the fungal flora and some microbial activities. 792 96

Two of 23 strains of Helicobacter pylori adapted from microaerobic to aerobic growth on blood agar plates incubated in humidified air. The air-adapted strains remained urease and phenylalanine deaminase positive and did not require the buffering effect of an enriched CO2 atmosphere for growth. The significance of this phenomenon remains to be determined as the two strains capable of aerobic metabolism were laboratory-adapted.
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PMID:Adaptation of Helicobacter pylori to aerobic growth. 807 Apr 55

A low ventilation model to induce ascites was introduced and characterized. In addition, the effect of supplemental air mixing via ceiling fans (CF) and the feeding of a urease inhibitor (0, 125, and 250 ppm) on incidence of ascites were investigated. Twelve environmental chambers were utilized in the trial; six were fitted with CF. Each dietary treatment was replicated twice per CF treatment. One hundred and twenty day-old male commercial broilers were reared per chamber. Atmospheric O2, CO2, and NH3, temperature, and humidity, as well as weekly litter moisture and pH, were monitored. Chamber CO2 levels increased immediately then stabilized. Chamber NH3 levels increased between 2 to 4 wk of age and rapidly declined when ventilation rates were increased to 1 cfm per bird. The CF and dietary treatments had little effect on air or litter variables except for NH3. Supplementing the diet with urease inhibitor resulted in a greater than 50% reduction in cumulative mortality due to ascites and a slight reduction in weekly BW gains. The CF treatment had no effect on production variables such as weekly feed intake, gain, and feed to gain ratio, or survivability due to ascites.
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PMID:Effect of a urease inhibitor and ceiling fans on ascites in broilers. 1. Environmental variability and incidence of ascites. 807 22

Texel wethers (68 +/- 2.5 kg BW) fitted with catheters in the ruminal veins and a mesenteric artery, blood flow probes on ruminal arteries, and a ruminal cannula were fed 500 g of orchardgrass hay every 12 h. During the last third of the feeding cycle, intraruminal injections were performed to evaluate the effect of urease activity, osmolality, and concentrations of NH3, butyrate, and CO2 in the rumen on urea and NH3 fluxes across the rumen wall. At pH 6.7, NH3 absorption increased with NH3 and butyrate concentrations in the rumen, and to a lesser extent with CO2 concentration. The increase in ruminal blood flow associated with CO2 and butyrate increase was always greater than the increase in NH3 absorption. Increasing ruminal osmolality slightly decreased NH3 absorption. Ruminal NH3 concentration and ruminal blood flow seemed to be the main determinant of NH3 absorption. Decreasing urease activity in the rumen decreased urea net transfer. The net transfer of urea to the rumen was stimulated by CO2. High concentrations of NH3 (330 mg of N/L) and butyrate (25 mM) in the rumen decreased urea net uptake, whereas osmolality (up to 420 mOsmol/L) did not affect it. Modifications in ruminal blood flow or water net movement across the ruminal wall did not seem to account for the effect of CO2, NH3, and butyrate on urea net uptake.
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PMID:Net transfer of urea and ammonia across the ruminal wall of sheep. 822 81

Urease in the human gastric mucosa is a marker for infection with Helicobacter pylori (HP), an organism which is associated with peptic ulcer disease. To detect gastric urease, we examined 184 patients (144 males, 40 females; mean age: 49.8 +/- 15.6 years) with suspected peptic ulcer disease. Fasting patients were given orally 5 microCi of carbon-14 labelled urea. From each patient only one breath sample was collected in hyamine at 10 min. The amount of 14C collected at 10 min was expressed as follows: [(DPM/mmol CO2 collected)/(DPM administered)] x 100 x body weight (kg). The presence of HP colonization was determined by examination of multiple endoscopic prepyloric antral biopsy specimens subjected to culture or a rapid urease test. For the purpose of this study, HP-positive patients were defined as those with characteristic bacteria as indicated by a positive result of either the culture or the rapid urease test; HP-negative patients were defined as those with negative findings on both the culture and the rapid urease test. Of the 184 cases, 99 (53.8%) were positive for HP infection, and 85 (46.2%), negative. The sensitivity and specificity of the rapid 10 min 14C-urea breath test for the diagnosis of HP-associated peptic ulcer disease were evaluated by a receiver operating characteristic (ROC) curve with a variable cut-off value from 1.5 to 4.5. When a cut-off value of 1.5 was selected, the sensitivity was 100% and the specificity, 83.5%; when a cut-off value of 4.5 was selected, the sensitivity was 54.5% and the specificity, 97.6%.
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PMID:Accuracy of a rapid 10-minute carbon-14 urea breath test for the diagnosis of Helicobacter pylori-associated peptic ulcer disease. 840 59

Klebsiella aerogenes urease in a Ni-containing enzyme (two Ni per alpha beta gamma unit) that is purified as an apoprotein from cells grown in Ni-free medium. Partial activation of urease and UreD-urease apoproteins is achieved in vitro by incubation in the presence of Ni(II) and CO2, whereas incubation of these proteins with Ni alone leads to the formation of inactive species [Park, I.-S., & Hausinger, R. P. (1995) Science 267, 1156-1158]. Here we determined the kinetics of these inhibitory reactions and demonstrated the presence of two Ni ions per alpha beta gamma unit in the inactive proteins. Although metal-substituted urease has never been purified from Ni-deprived cell, several other metal ions were shown to bind to the urease apoproteins. Divalent Zn, C, Co, and Mn all inhibited Ni- and Co2-promoted urease activation at concentrations below that of Ni, whereas Mg and Ca ions did not inhibit this process. Ni-inhibited species recovered their ability to be partially activated after EDTA treatment. In contrast, samples that were exposed to Co or Cu ions were irreversibly inactivated, and EDTA treatment of Zn- or Mn-inhibited samples led to reduced levels of activation competence. Mn-substituted urease, generated from urease apoprotein samples in a Mn- and Co2-dependent manner, was shown to be active, whereas other metal-substituted forms if urease lacked activity. The Mn-protein possessed only 2% of the activity of Ni-activated apoprotein [ approximately 8.0 vs approximately 400 mumol min-1 (mg protein)-1], but its KM value was only moderately altered from that of the native enzyme (3.86 +/- 0.15 mM vs 0.2 mM). Unlike the Ni-containing enzyme, Mn-urease was inhibited by EDTA. Given the evidence that urease apoprotein binds numerous metal ions, we speculate on possible roles for the UreD, UreF, and UreG accessory proteins in urease activation.
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PMID:Metal ion interaction with urease and UreD-urease apoproteins. 861 23

Helicobacter pylori has been implicated as an agent in the pathogenesis of antral gastritis, gastric and duodenal ulcer and probably in gastric cancer. The C13 urea breath test is a diagnostic method quick to perform, sensitive, reliable and non invasive. It is based on the presence of Helicobacter pylori urease activity, which permits to detect it in the infected mucosa. A substrate (urea) labelled with Carbon 13 is administered to the patient and exhaled breath is collected to detect the possible catabolism product (CO2 labelled with C13). In the European protocol, patients in fasting condition are given a test meal to delay gastric emptying and five minutes later a solution which contents 100 mg of C13 labelled urea. Breath samples are collected before and 30 minutes after urea was given. In our first year of experience, 363 patients with Helicobacter pylori infection detected by histology or urease were studied by C13 urea breath test, with a sensitivity and specificity of 95 and 96%. False negatives may occur if the test is used after antibiotics and other antiulcer drugs. Its main indication is to monitor eradication therapy after treatment. Its possible use as a quantitative test still remains unclear.
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PMID:[C13 urea breath test in the diagnosis of Helicobacter pylori infection in the gastric mucosa. Validation of the method]. 864 14

We have devised a procedure that permits the cultivation of a gram-positive coccoid species from biopsy material obtained from the antrum of the stomachs of patients with gastric disorders. Antibodies directed against surface proteins obtained from the coccoid isolates were detected in all patients with gastric disorders examined in this study, including both Helicobacter pylori-infected and H. pylori-uninfected patients. Several of these isolates, including a prototype designated strain SL100, have been characterized in some detail. Strain SL100 exhibits urease and exceptionally high catalase activities and assumes a variety of spherical morphologies as detected by electron microscopy. This isolate expresses an adhesin that binds to gastric mucin. The adhesin activity was detected only after the isolate was exposed to an acidic pH, suggesting that in the natural process of infection, the low pH of the stomach unmasks a cell surface component with adhesin activity. Strain SL100 grows best under a microaerophilic conditions (10% CO2, 5% O2, 85% N2), but it also grows quite well under aerobic conditions. Thus, this organism would be expected to proliferate outside of the human host as well as in the gastric mucosa. Oral infection of newborn piglets resulted in colonization of the gastric antrum and growth retardation. Preliminary taxonomic classification indicates similarity to the Staphylococcus DNA homology groups containing S. cohnii and S. xylosus. One of us (C.K.) apparently became infected with this organism as indicated by gastric symptoms and the subsequent presence of strain-specific antisera not present in other workers in the laboratory.
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PMID:Successful cultivation of a potentially pathogenic coccoid organism with trophism for gastric mucin. 897 91

1. Stable urea isotopes can be used to study urea kinetics in humans. The use of stable urea isotopes for studying urea kinetic parameters in humans on a large scale is hampered by the high costs of the labelled material. We devised a urea dilution for measurement of the distribution volume, production rate and clearance of urea in healthy subjects and renal failure patients using the inexpensive single labelled [13C]urea isotope with subsequent analysis by headspace chromatography-isotope ratio MS (GC-IRMS) of the [13C]urea enrichment. 2. The method involves measurement of the molar percentage excess of [13C]urea in plasma samples taken over a 4 h period after an intravenous bolus injection of [13C]urea. During the sample processing procedure, the plasma samples together with calibration samples containing a known molar percentage excess of [13C]urea are acidified with phosphoric acid to remove endogenous CO2, and are subsequently incubated with urease to convert the urea present in the plasma samples into CO2. The 13C enrichment of the generated CO2 is analysed by means of GC-IRMS. This method allows measurement of the molar percentage excess of [13C]urea to an accuracy of 0.02%. 3. Reproducibility studies showed that the sample processing procedure [within-run coefficient of variation (CV) < 2.8% and between-run CV < 8.8%] and the GC-IRMS analysis (within-day CV < 1.3% and between-day CV < 1.3%) could be repeated with good reproducibility. 4. In clinical urea kinetic studies in a healthy subject and in a renal failure patient without residual renal function, reproducible values of the distribution volume, production rate and clearance of urea were determined using minimal amounts of [13C]urea (25-50 mg). 5. Because only low [13C]urea enrichments are needed in this urea dilution method using GC-IRMS analysis, the costs of urea kinetic studies are reduced considerably, especially in patients with renal failure.
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PMID:Determination of urea kinetics by isotope dilution with [13C]urea and gas chromatography-isotope ratio mass spectrometry (GC-IRMS) analysis. 927 6

Urease possesses a dinuclear nickel active site with the metals bridged by a carbamylated lysine residue. In vitro activation of apoprotein (Apo) is achieved by incubation with Ni(II) and bicarbonate as a source of CO2. Analogues of CO2 and bicarbonate were examined for their effects on the Apo activation process. While SO2 had little effect, CS2 was shown to inhibit Apo activation via its ability to substitute for CO2 to yield an inactive dithiocarbamate-containing protein. Sulfur-to-Ni charge-transfer transitions arising from this species yielded an electronic absorption band at 324 nm with a shoulder at 382 nm. Borate, sulfate, phosphate, and molybdate had essentially no effect on Apo activation and did not substitute for bicarbonate, while treatment of Apo with Ni(II) plus vanadate led to the production of active urease containing two Ni and one V per active site. Vanadate-dependent activation of Apo resembled the normal activation process in terms of concentration of anion required, optimal pH, and incubation time needed. Furthermore, the UV-visible spectrum, maximal specific activity [386 +/- 26 U.(mg of protein)-1], Km (1.83 +/- 0.20 mM urea), and pH dependence for the vanadate-containing urease were essentially identical to properties observed for bicarbonate-activated enzyme. Vanadate-activated Apo is proposed to possess a vanadylated lysine that bridges the two Ni ions comprising its metallocenter.
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PMID:Substitution of the urease active site carbamate by dithiocarbamate and vanadate. 939 39


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