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)

The study on the calatase, polyphenol-oxidase, invertase, urease and phosphatase activities in Paeonia ostii rhizosphere and non-rhizosphere soil of Tongling copper mining showed that all test enzyme activities were higher in rhizosphere than in non-rhizosphere soil. Soil calatase, urease and phosphatase were sensitive to heavy metals pollution, and their activities could be used as the indicators of heavy metals' joint pollution. The effects of rhizosphere environment on the soil enzyme activities were in the sequence of phosphatase > urease > calatase > invertase > polyphenol-oxidase, and the affecting rate was 131.562%, 92.492%, 87.557%, 59.673% and 34.076%, respectively. The test enzyme activities were negatively correlated with soil heavy metals pollution, and the correlation coefficients were all higher than -0.898, suggesting the inhibitory effects of heavy metals' joint pollution on soil enzyme activities. P. ostii could effectively improve soil environment, and thus, enhance the activities of soil enzymes.
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PMID:[Enzyme activities in Paeonia ostii rhizosphere and non-rhizosphere soil of Tongling copper mining]. 1704 14

The microenvironments of the sol-gel-derived urease biosensors in terms of elemental ratio, surface morphology, specific surface area and pore size were investigated to characterize the physicochemical properties of poly(vinyl alcohol) (PVA)-modified sol-gel materials. X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and surface area analyzer were used to identify the surface species, topography and pore distribution of the organically doped sol-gel network. XPS results showed that stoichiometric ratios of oxygen-to-silicon in sol-gel materials were in the range 2.08-2.11. The sol-gel materials were partially dried and negatively charged, which retained 6-8% water content to maintain urease activity. The surface morphology of the sol-gel altered obviously when macromolecules were encapsulated, resulting in the increase in surface mean roughness from 0.207 to 2.636 nm. The specific surface area decreased dramatically after the immobilization of biomolecules and organic additives, which clearly depicts that PVA and urease were co-encapsulated into the sol-gel network. However, there still exist enough pore volumes for analytes to mass transport. The apparent Michaelis-Menten constant value (Km) of the encapsulated urease was similar to that in solution and the overall catalytic efficiency in PVA-doped sol-gel-derived glasses only decreased by a factor of 3.2 relative to the value in solution. In addition, the analytical performance of the entrapped urease in PVA-doped sol-gel materials was examined by determining the Cu(II) concentration in aqueous solution. The analytical range of Cu(II) was in the range 2x10(-6) to 2x10(-2) M with a detection limit of 1.5 microg L(-1). Results obtained in this study demonstrate a strategy for maintaining urease activity for biomedical and environmental applications.
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PMID:Preparation and characterization of urease-encapsulated biosensors in poly(vinyl alcohol)-modified silica sol-gel materials. 1747 71

The two Ni2+ ions in the urease active site are delivered by the metallochaperone UreE, whose metal binding properties are central to the assembly of this metallocenter. Isothermal titration calorimetry (ITC) has been used to quantify the stoichiometry, affinity, and thermodynamics of Ni2+, Cu2+, and Zn2+ binding to the well-studied C-terminal truncated H144*UreE from Klebsiella aerogenes, Ni2+ binding to the wild-type K. aerogenes UreE protein, and Ni2+ and Zn2+ binding to the wild-type UreE protein from Bacillus pasteurii. The stoichiometries and affinities obtained by ITC are in good agreement with previous equilibrium dialysis results, after differences in pH and buffer competition are considered, but the concentration of H144*UreE was found to have a significant effect on metal binding stoichiometry. While two metal ions bind to the H144*UreE dimer at concentrations <10 microM, three Ni2+ or Cu2+ ions bind to 25 microM dimeric protein with ITC data indicating sequential formation of Ni/Cu(H144*UreE)4 and then (Ni/Cu)2(H144*UreE)4, or Ni/Cu(H144*UreE)2, followed by the binding of four additional metal ions per tetramer, or two per dimer. The thermodynamics indicate that the latter two metal ions bind at sites corresponding to the two binding sites observed at lower protein concentrations. Ni2+ binding to UreE from K. aerogenes is an enthalpically favored process but an entropically driven process for the B. pasteurii protein, indicating chemically different Ni2+ coordination to the two proteins. A relatively small negative value of DeltaCp is associated with Ni2+ and Cu2+ binding to H144*UreE at low protein concentrations, consistent with binding to surface sites and small changes in the protein structure.
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PMID:Thermodynamics of Ni2+, Cu2+, and Zn2+ binding to the urease metallochaperone UreE. 1771 1

Analysis of the structure and inventory of the genome of Nitrosomonas eutropha C91 revealed distinctive features that may explain the adaptation of N. eutropha-like bacteria to N-saturated ecosystems. Multiple gene-shuffling events are apparent, including mobilized and replicated transposition, as well as plasmid or phage integration events into the 2.66 Mbp chromosome and two plasmids (65 and 56 kbp) of N. eutropha C91. A 117 kbp genomic island encodes multiple genes for heavy metal resistance, including clusters for copper and mercury transport, which are absent from the genomes of other ammonia-oxidizing bacteria (AOB). Whereas the sequences of the two ammonia monooxygenase and three hydroxylamine oxidoreductase gene clusters in N. eutropha C91 are highly similar to those of Nitrosomonas europaea ATCC 19718, a break of synteny in the regions flanking these clusters in each genome is evident. Nitrosomonas eutropha C91 encodes four gene clusters for distinct classes of haem-copper oxidases, two of which are not found in other aerobic AOB. This diversity of terminal oxidases may explain the adaptation of N. eutropha to environments with variable O(2) concentrations and/or high concentrations of nitrogen oxides. As with N. europaea, the N. eutropha genome lacks genes for urease metabolism, likely disadvantaging nitrosomonads in low-nitrogen or acidic ecosystems. Taken together, this analysis revealed significant genomic variation between N. eutropha C91 and other AOB, even the closely related N. europaea, and several distinctive properties of the N. eutropha genome that are supportive of niche specialization.
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PMID:Whole-genome analysis of the ammonia-oxidizing bacterium, Nitrosomonas eutropha C91: implications for niche adaptation. 1799 Oct 28

The toxicity of the trace metals Cd, Cu, and Pb alone and in combination was assessed by measuring the activity of the soil enzymes dehydrogenase and urease. We assayed the enzymatic response of a forest soil exposed to single metals and metal mixtures in a factorial design. The chemical speciation of the metals was measured in 0.01M KNO3 solution extracts using an ion-selective electrode for Cu2+ and estimated from voltammetric determinations of labile metals for Cd2+ and Pb2+. The toxicity interaction of the metal mixtures was predicted according to the classical Bliss independence and Loewe additivity models. Significant antagonistic effects were observed for the majority of the combinations for both the dehydrogenase and the urease assays. Given the strong interaction upon the chemistry, the toxicity interaction data were analyzed based on resulting free metal activities to tease out the effect of chemistry changes from that of toxicological responses. As a result, a stimulation of enzymatic activities was observed in the mixtures in comparison to the enzymatic activities obtained with the individual metal.
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PMID:Toxicity interactions of cadmium, copper, and lead on soil urease and dehydrogenase activity in relation to chemical speciation. 1806 81

A greenhouse pot experiment was conducted to evaluate the effect of sewage sludge (SS), of sugar beet sludge (SBS), or of a combination of both, in the remediation of a highly acidic (pH 3.6) metal-contaminated soil, affected by mining activities. The SS was applied at 100 and 200 Mg ha(-1) (dry weight basis), and the SBS at 7 Mg ha(-1). All pots were sown with Italian ryegrass (Lolium multiflorum Lam.). After 60 d of growth, shoot biomass was quantified and analysed for Cu, Pb and Zn. The pseudo-total and bioavailable contents of Cu, Pb and Zn and the enzymatic activities of beta-glucosidase, acid phosphatase, cellulase, protease and urease were determined in the soil mixtures. Two indirect acute bioassays with leachates from the soil (luminescent inhibition of Vibrio fischeri and Daphnia magna immobilization) were also used. The SS, in particular when in combination with SBS, corrected soil acidity, while increasing the total organic matter content and the cation exchange capacity. The application of SS led to a decrease in the level of effective bioavailable metals (extracted by 0.01 M CaCl(2), pH 5.7, without buffer), but caused an increase in their potential bioavailability (extracted by a solution of 0.5M NH(4)CH(3)COO, 0.5 M CH(3)COOH and 0.01 M EDTA, pH 4.7). Plant biomass increased more than 10 times in the presence of 100 Mg SS ha(-1), and more than five times with the combined use of 100 Mg SS ha(-1) and SBS, but a considerable phytotoxic effect was observed for the application rate of 200 Mg SS ha(-1). Copper, Pb and Zn concentrations in the shoots of L. multiflorum decreased significantly when using 100 Mg SS ha(-1) or SBS. The activities of beta-glucosidase, urease and protease increased with increasing SS applications rates, but cellulase had a reduced activity when using 200 Mg ha(-1)SS. Both amendments were able to suppress soil toxicity to levels that did not affect D. magna, but increased the soil leachate toxicity towards V. fischeri, especially with the application of 200 Mg SS ha(-1). This study showed that for this type of mine soils, and when using SS of similar composition, the maximum SS application rate should be 100 Mg ha(-1), and that liming the SS amended soil with SBS did not contribute to a further improvement in soil quality.
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PMID:Assessment of chemical, biochemical and ecotoxicological aspects in a mine soil amended with sludge of either urban or industrial origin. 1854 5

A heavy-metal assay has been developed using bromelain, a protease. The enzyme is assayed using casein as a substrate with Coomassie dye to track completion of hydrolysis of casein. In the absence of inhibitors, casein is hydrolysed to completion, and the solution is brown. In the presence of metal ions such as Hg2+ and Cu2+, the hydrolysis of casein is inhibited, and the solution remains blue. Exclusion of sulfhydryl protective agent and ethylenediaminetetraacetic in the original assay improved sensitivity to heavy metals several fold. The assay is sensitive to Hg2+ and Cu2+, exhibiting a dose-response curve with an IC50 of 0.15 mg 1(-1) for Hg2+ and a one-phase binding curve with an IC50 of 0.23 mg 1(-1) for Cu2+. The IC50 value for Hg2+ is found to be lower to several other assays such as immobilized urease and papain assay, whilst the IC50 value for Cu2+ is lower than immobilized urease, 15-min Microtox, and rainbow trout.
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PMID:An inhibitive determination method for heavy metals using bromelain, a cysteine protease. 1855 17

The inhibition of urease by heavy metal ions has been habitually ascribed to the reaction of the ions with enzyme thiol groups, resulting in the formation of mercaptides. To probe the modes of metal binding to the enzyme, in this work the reaction of mono- (Ag, Hg) and di- (Cu, Hg) valent metal ions with jack bean urease was studied. The enzyme was reacted with different concentrations of the metal ions for different periods of times, when its residual activity was assayed and thiol content titrated. The titration carried out with DTNB was done to examine the involvement of urease thiol groups in metal ion binding. The binding was further probed by reactivation of the metal ion-enzyme complexes with DTT, EDTA and dilution. The results are discussed in terms of the HSAB concept. In inhibiting urease the metal ions showed a common feature in that they inhibited the enzyme within a comparable micromolar range, and also in that their inhibition was multisite. By contrast, the main distinguishing feature in their action consisted of the involvement of enzyme thiol groups in the reaction. Hg (2+) and Hg2(2+) inhibition was found thoroughly governed by the reaction with the enzyme thiols, and the complete loss of enzyme activity involved all thiols available in the enzyme under non-denaturating conditions. In contrast, Ag+ and Cu2+ ions for the complete inactivation of the enzyme required 53 and 60% of thiols, respectively. Accordingly, Ag+ and Cu2+ binding to functional groups in urease other than thiols, i.e. N- and O-containing groups, cannot be excluded. Based on the reactivation experiments this seems particularly likely for Cu2+, whose concurrent binding to thiols and other groups might distort the architecture of the active site (the mechanism of which remains to be elucidated) resulting in the observed inhibitory effects.
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PMID:Mono- (Ag, Hg) and di- (Cu, Hg) valent metal ions effects on the activity of jack bean urease. Probing the modes of metal binding to the enzyme. 1860 77

In the present study, the utilization of dilute CaCl2 extraction and free metal ion activity was tested for its ability to predict urease activity in soils that was measured by a simple and rapid urease assay. Two soil series (an Arkport sandy loam and a Hudson silty clay loam) were spiked with Cu and Zn, both singly and in combination, and then field aged for over a year prior to use. For both the metal-spiked Arkport and Hudson soils, much of the inhibition in measured urease activity was explained by increased CaCl2-extractable Cu, with a lesser effect from increased Zn extractability. A positive but weak interaction between Cu and Zn suggested by regression analysis indicates the toxicity of Cu-Zn mixtures to soil urease is slightly less than additive (antagonistic). Copper extractability using CaCl2 was able to predict urease activity in only one of the tested soils. By contrast, measurements of Cu2+ activity were predictive of reduced urease activity in both soils (R2adj = 0.726, p < 0.0001), indicating that Cu2+ activity is a more useful predictor of urease inhibition in soils than CaCl2-extractable Cu. The present study also highlighted the importance that clay mineral content had on controlling the availability of added metals in soils over time since a greater aging effect on Cu toxicity was found for the fine-textured Hudson than the coarse-textured Arkport soil.
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PMID:Urease activity in aged copper and zinc-spiked soils: relationship to CaCl2-extractable metals and Cu2+ activity. 1869 75

A urea biosensor prepared by covalent binding of urease directly to the surface of an ammonium-sensitive field effect transistor (FET) is described. Nonactin incorporated in carboxylated polyvinyl chloride was used to obtain the sensitive membrane of the ammonium-sensitive FET. The grafting of urease on the polyvinylchloride-COOH membrane surface was performed through carbodiimide coupling. The activity of the immobilized enzyme was spectrometrically controlled through the time-dependent disappearance of the absorbance of NADH at 340 nm. An apparent activity of 50% was found, compared with free enzyme. The sensitivity of the urea enzyme FET is 50 mV/pUrea working in a differential mode of 2 muM to 1 mM, this sensitivity being constant during 15 days. Finally, in order to test the potentialities of the urea biosensor for the environmental applications, the detection of heavy metal ions such as Cu(II) and Hg(II) in solution was performed by measuring the remaining activity of the inhibited enzyme.
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PMID:A miniaturized urea sensor based on the integration of both ammonium based urea enzyme field effect transistor and a reference field effect transistor in a single chip. 1896 11


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