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)

UreE is proposed to be a metallochaperone that delivers nickel ions to urease during activation of this bacterial virulence factor. Wild-type Klebsiella aerogenes UreE binds approximately six nickel ions per homodimer, whereas H144*UreE (a functional C-terminal truncated variant) was previously reported to bind two. We determined the structure of H144*UreE by multi-wavelength anomalous diffraction and refined it to 1.5 A resolution. The present structure reveals an Hsp40-like peptide-binding domain, an Atx1-like metal-binding domain, and a flexible C terminus. Three metal-binding sites per dimer, defined by structural analysis of Cu-H144*UreE, are on the opposite face of the Atx1-like domain than observed in the copper metallochaperone. One metal bridges the two subunits via the pair of His-96 residues, whereas the other two sites involve metal coordination by His-110 and His-112 within each subunit. In contrast to the copper metallochaperone mechanism involving thiol ligand exchanges between structurally similar chaperones and target proteins, we propose that the Hsp40-like module interacts with urease apoprotein and/or other urease accessory proteins, while the Atx1-like domain delivers histidyl-bound nickel to the urease active site.
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PMID:Crystal structure of Klebsiella aerogenes UreE, a nickel-binding metallochaperone for urease activation. 1159 23

Coccidioides immitis, the causative agent of San Joaquin Valley fever (coccidioidomycosis), produces a urease which has been suggested to contribute to the virulence of this fungal pathogen. Urease catalyzes the hydrolysis of urea and has been proposed to at least partly account for alkalinity of the microenvironment in which C. immitis grows due to the release of ammonia and ammonium ions. The C. immitis urease was purified to homogeneity (1048-fold) from the mycelial cytosol by chromatographic fractionation. The sequence of 12 N-terminal amino-acid residues of the purified, native polypeptide was identical to that predicted by the translated urease gene sequence which has been reported. The isolated enzyme exhibited a specific activity in the presence of urea of 1750 micromol min(-1) mg(-1) protein, has a native molecular mass of 450 kDa, revealed a Km for urea of 4.1 mM, had a pH optimum of 8.0 and is heat stable. Hydroxyurea, acetohydroxamic acid (AHA) and boric acid each inhibited activity of the purified enzyme. Urease activity was enhanced by the presence of 5-10 mM concentrations of Mg2+ or Mn2+, but inhibited by Li+, Ni2+, Cu2+ or Zn2+. The reversible urease inhibitor, AHA, blocked enzyme activity in the crude mycelial cytosolic fraction when added at a concentration of 10 mM. On the other hand, 10 mM AHA added to 4-day-old mycelial cultures only partially decreased the amount of ammonium detected in the culture medium. It is evident, therefore, that C. immitis urease activity does not account for the total amount of ammonia secreted during in vitro growth of the pathogen. Other metabolic sources of ammonia, which may also contribute to the virulence of C. immitis, are under investigation.
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PMID:Purification and characterization of urease isolated from the pathogenic fungus Coccidioides immitis. 1186 12

A sensitive dip-and-read test strip for the determination of mercury in aqueous samples based on the inhibition of urease reaction by the ion has been developed. The strip has a circular sensing zone that containing two layers: the top layer is a cellulose acetate membrane where urease is immobilized on it; the bottom layer is a pH indicator wafer that is impregnated with urea. The principle of the measurement is based on the disappearance of a yellow spot on the pH indicator wafer. The elapsing time until the disappearance of the spot which depends on the concentration of mercury(II) ion is measured with a stopwatch. Under the experimental conditions, as low as 0.2 ng/ml mercury can be observed with the detection range from 0.2 to 200 ng/ml in water. Organomercury compounds give essentially the same response as inorganic mercury. Heavy-metal ions such as Ag(I), Cu(II), Cd(II), Ni(II), Zn(II), and Pb(II) as well as other sample matrixes basically do not interfere with the mercury measurement.
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PMID:A dip-and-read test strip for the determination of mercury(II) ion in aqueous samples based on urease activity inhibition. 1245 6

A method for the quantification of urease enzyme activity has been set up, which is based on the quantification of carbon dioxide set free into the head space of gastight vessels. The method can be applied for ecotoxicological characterisation of contaminated soil samples besides other methods like soil respiration measurements or nitrification inhibition tests. The sieved soil sample can be incubated under nearly natural conditions with an adjusted water content of about 50% of the water holding capacity. Ammonia or urea do not need to be extracted, since carbon dioxide release is correlated to urease activity. Thus carbon dioxide release is a direct result of urease activity which can be measured in the head space using gastight syringes and gaschromatographic equipment. The urease activity is determined by comparing the carbon dioxide release of incubation vessels with and without urea supply. The applicability of this method has been demonstrated by experiments with N-(n-butyl)phosphoric triamide (NBPT), copper ions and zinc ions as known inhibitors of urease activity.
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PMID:Determination of urease activity in soils by carbon dioxide release for ecotoxicological evaluation of contaminated soils. 1246 82

This study demonstrated a general reduction in photosynthesis (carbon fixation, O(2)-evolution and photochemical electron transport chain), the uptake of NH(4)(+), NO(3)(-), urea and PO(4)(3+), and activities of nitrate reductase, urease, acid phosphatase and ATPase following UV-B and copper exposure of Chlorella vulgaris in the absence or presence of 1 and 2 ppm concentrations of a 4-inch-thick ozone layer. Though the effect of stressors used in combination was very detrimental to the above processes, selected concentrations of ozone not only counteracted the UV-B-induced inhibition of the above processes, but also stimulated O(2)-evolution and the photochemical electron transport chain. Kinetics of nutrient uptake and enzyme activities demonstrated that UV-B causes structural change(s) in the enzymes/carriers responsible for the uptake of NH(4)(+), NO(3)(-), urea and PO(4)(3+) as well as their assimilatory enzymes. Except for nitrate reductase, copper was found to compete for the binding sites of all the above enzymes. Synergistic inhibition of photosynthetic activity, nutrient (except NH(4)(+)) uptake, and enzyme activities by UV-B+Cu seems to be due to increased Cu uptake as a consequence of altered membrane permeability brought about by the peroxidation of membrane lipids in UV-B-exposed cells.
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PMID:Interactive effects of UV-B and Cu on photosynthesis, uptake and metabolism of nutrients in a green alga Chlorella vulgaris under simulated ozone column. 1250 15

A simple optical fibre biosensor based on immobilised enzyme for monitoring of trace heavy metal ions has been developed. The biosensor recognition system was designed based on the inhibition of urease activity, where the urease is immobilised on ultrabind membrane. The studies of inhibition by the heavy metal ions Hg(II), Ag(I), Cu(II), Ni(II), Zn(II), Co(II) and Pb(II) were performed using a fibre-optic biosensor configuration, where the pH change resulting from the bio-catalytic hydrolysis of urea was monitored at the wavelength 615 nm spectroscopically, using commercial pH indicator strip before and after the exposure to the heavy metal ions. The immobilised urease was regenerated by l-cysteine. The linear response range between 1 x 10(-9)-1 x 10(-5) M and the limit of detection 1 x 10(-9 )M (0.2 microg/L) for Hg(II) ions was achieved by employing the flow method. The optimisation of experimental parameters, including flow method, is also discussed.
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PMID:Simple optical fibre biosensor based on immobilised enzyme for monitoring of trace heavy metal ions. 1285 31

From the open investigation and laboratory analysis, this paper studied the vegetation state and soil enzyme activities of copper tailing yard of Tongguan mountain. The results showed that there were 34 species of natural colonized plants on copper tailing yard, subordinated to 16 families and 33 genera, and regard herbs as principle, and many for 1-2 years old. The main families were compositae (10 species), gramineae (9 species) and legumineceae (2 species). Hippochaete ramosissimum, which belonged to equisetaceae, had and significant dominant. There were some microcoenses such as Hippochaete ramosissimum + Imperata cylindraca community, Cynodon dactylon + Imperata cylindraca community and Phragmites australis community. But, the vegetation on copper tailing yard was distributed in spot piece and scattered mainly with single species. The activities of three soil enzymes had a stronger sensitivity to the vegetation state, and their relativity to the vegetation state was in order of urease > sucrase > catalase. It's suggested that unrease activity could be used as an indicator index for the reclamation of wasteland.
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PMID:[Vegetation state and soil enzyme activities of copper tailing yard on Tongguan mountain]. 1292 35

Studies on the soil microbes, soil enzyme activity and soil biochemical intensity in copper mining wasteland indicated that the total quantity of major soil microbes declined by 68.43%-80.32%, compared with that of the non-minig soil. The proportion of bacteria and actinomyces decreased, while that of fungi did not changed obviously. The amount of major physiological groups including ammonifiers, nitrogen fixing bacteria, cellulose decomposing bacteria, aerobic nitrogen fixing bacteria and anaerobic nitrogen fixing bacteria all decreased, and soil basic respiration descended, compared with the control. The activity of soil enzymes weakened, which included urease, sucrase, proteinase, acid phosphtase, peroxidase, polyphenol oxidase and dehydrogenase. Soil biochemical intensity including ammonification, nitrification, nitrogen fixation and cellulose decomposition descended, and the circulation of C and N in mining soil inhibited. All the results showed that the weakening of microbial activity was one of major characteristics in reclaimed mining soil.
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PMID:[Microbial eco-characteristics of reclaimed mining wasteland in red soil area of southern China. I. Effects on soil microbial activity]. 1499 48

Studies on the enzyme activities and heavy metal contents in soils polluted by abandoned copper tailings showed that the contents of heavy metals in contaminated soils were higher than those in no-polluted soils, and the enzyme activities, especially dehydrogenase and urease activities were decreased significantly with increasing contamination. Multivariate regression analysis indicated that soil dehydrogenase activity was very significantly correlated with the combined effect of several heavy metals, and urease, protease or acid phosphatase activity was significantly related to the combined effect of them. The total enzyme activity of soil might be a useful index in management of these highly contaminated soils, and hence, it is feasible to use this index as a primary biochemical parameter to evaluate heavy metals compound pollution.
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PMID:[Enzyme activities in soils contaminated by abandoned copper tailings]. 1499 60

An amperometric assay based on urease inactivation has been developed for the screening of heavy metals in environmental samples. The enzyme urease catalyses the hydrolysis of urea and the formation of NH(4)(+) is determined using a NADH-glutamate dehydrogenase coupled reaction system. NADH consumption is monitored amperometrically using screen-printed three electrode configuration and its oxidation current is then correlated to urease activity. The presence of heavy metals in the samples inhibits the urease activity, resulting in a lower NH(4)(+) production and therefore a decrease in NADH oxidation. The use of metallised carbon electrodes gave a decrease in NADH oxidation potential from +300 mV versus Ag/AgCl compared with > +600 mV for bare carbon electrodes, and thus minimised interferences from oxidizable species present in the samples. Electrodes fouling and possible contamination after reuse and cleaning was also eliminated by using screen-printed disposable electrodes. The linear range obtained for Hg(II) and Cu(II) was 10-100 microgl(-1) with a detection limit of 7.2 microgl(-1) and 8.5 microgl(-1), respectively. Cd(II) and Zn(II) produced enzyme inhibition in the range 1-30 mgl(-1), with limits of detection of 0.3 mgl(-1) for Cd(II) and 0.2 mgl(-1) for Zn(II). Pb(II) did not inactivate the urease enzyme significantly at the studied range (up to 50 mgl(-1)). Coefficients of variation (CV) values were 6-9% in all cases. Application of the assay system to leachate samples gave reliable and accurate toxicity assessments when compared to atomic absorption spectrometry (AAS) and inductively coupled plasma atomic emission spectroscopy (ICP-MS) analysis. This approach provides to be a simple and rapid (15 min, including enzyme inhibition time) method for metal ions detection.
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PMID:Development of urease and glutamic dehydrogenase amperometric assay for heavy metals screening in polluted samples. 1504 46


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