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 influence of the primary structures of plant (Canavalia ensiformis) and bacterial (Bacillus pasteurii) ureases on the precipitation of calcium carbonate polymorphs in solutions of calcium salts and urea at room temperature was investigated. Despite a similar catalytic function in the decomposition of urea, these ureases exerted different influences on the crystal phase formation and on the development of unusual morphologies of calcium carbonate polymorphs. Spherical and uniform vaterite particles were precipitated rather than calcite in the presence of Bacillus urease, while the presence of Canavalia urease resulted in the precipitation of calcite only. Vaterite particles were shown to be built up of nanosized crystallites, proving the importance of nanoscale aggregation processes on the formation of colloidal carbonates. Reduction of the concentration of Bacillus urease in the reacting solution results in the formation of calcite crystals with a more complex surface morphology than the ones obtained by Canavalia urease. These differences may be explained by dissimilarities in the amino acid sequences of the two examined ureases and their different roles in nucleation and physicochemical interactions with the surface of the growing crystals, during the precipitation processes. This study exemplifies the diversity of proteins produced by different organisms for the same function, and the drastic effects of subtle differences in their primary structures on crystal phase formation and growth morphology of calcium carbonate precipitates, which occur as inorganic components in a large number of biogenic structures.
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PMID:Influence of the primary structure of enzymes on the formation of CaCO2 polymorphs: a comparison of plant (Canavalia ensiformis) and bacterial (Bacillus pasteurii) ureases. 1614 73

The effect of heavy metal contamination on biological and biochemical properties of Italian volcanic soils was evaluated in a multidisciplinary study, involving pedoenvironmental, micromorphological, physical, chemical, biological and biochemical analyses. Soils affected by recurring river overflowing, with Cr(III)-contaminated water and sediments, and a non-flooded control soil were analysed for microbial biomass, total and active fungal mycelium, enzyme activities (i.e., FDA hydrolase, dehydrogenase, beta-glucosidase, urease, arylsulphatase, acid phosphatase) and bacterial diversity (DGGE characterisation). Biological and biochemical data were related with both total and selected fractions of Cr and Cu (the latter deriving from agricultural chemical products) as well as with total and extractable organic C. The growth and activity of soil microbial community were influenced by soil organic C content rather than Cu or Cr contents. In fact, positive correlations between all studied parameters and organic C content were found. On the contrary, negative correlations were observed only between total fungal mycelium, dehydrogenase, arylsulphatase and acid phosphatase activities and only one Cr fraction (the soluble, exchangeable and carbonate bound). However, total Cr content negatively affected the eubacterial diversity but it did not determine changes in soil activity, probably because of the redundancy of functions within species of soil microbial community. On the other hand, expressing biological and biochemical parameters per unit of total organic C, Cu pollution negatively influenced microbial biomass, fungal mycelium and several enzyme activities, confirming soil organic matter is able to mask the negative effects of Cu on microbial community.
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PMID:Impact of river overflowing on trace element contamination of volcanic soils in south Italy: part II. Soil biological and biochemical properties in relation to trace element speciation. 1640 24

Bismuth compounds are widely used for the treatment of peptic ulcers and Helicobacter pylori infections. It has been suggested that enzyme inhibition plays an important role in the antibacterial activity of bismuth towards this bacterium. Urease, an enzyme that converts urea into ammonia and carbonic acid, is crucial for colonization of the acidic environment of the stomach by H. pylori. Here, we show that three bismuth complexes exhibit distinct mechanisms of urease inhibition, with some differences dependent on the source of the enzyme. Bi(EDTA) and Bi(Cys)(3) are competitive inhibitors of jack bean urease with K(i) values of 1.74 +/- 0.14 and 1.84 +/- 0.15 mM, while the anti-ulcer drug, ranitidine bismuth citrate (RBC) is a non-competitive inhibitor with a K (i) value of 1.17 +/- 0.09 mM. A (13)C NMR study showed that Bi(Cys)(3) reacts with jack bean urease during a 30 min incubation, releasing free cysteines from the metal complex. Upon incubation with Bi(EDTA) and RBC, the number of accessible cysteine residues in the homohexameric plant enzyme decreased by 5.80 +/- 0.17 and 11.94 +/- 0.13, respectively, after 3 h of reaction with dithiobis(2-nitrobenzoic acid). Kinetic analysis showed that Bi(EDTA) is both a competitive inhibitor and a time-dependent inactivator of the recombinant Klebsiella aerogenes urease. The active C319A mutant of the bacterial enzyme displays a significantly reduced sensitivity toward inactivation by Bi(EDTA) compared with the wild-type enzyme, consistent with binding of Bi(3+) to the active site cysteine (Cys(319)) as the mechanism of enzyme inactivation.
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PMID:Inhibition of urease by bismuth(III): implications for the mechanism of action of bismuth drugs. 1693 56

Continuous layers of hydroxyapatite were deposited on silk cloth from aqueous solutions by using urease as the precipitant supplier. Silk cloth was surface-modified with urease and was immersed in an aqueous solution containing Ca2+, PO4(3-) , and urea. As urea was hydrolyzed to form ammonia with the aid of the immobilized urease, hydroxyapatite precipitated predominantly on the surface of the silk cloth. It took only a few hours to form continuous layers of hydroxyapatite on the silk cloth. The resultant hydroxyapatite was found to be bone-like apatite because it had low crystallinity, contained carbonate ion in the lattice, and had a calcium-deficient composition.
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PMID:Deposition of bone-like hydroxyapatite on the surface of silk cloth with the aid of immobilized urease. 1724 3

Cellulose microfibers were coated with enzymes, laccase and urease, through layer-by-layer assembly by alternate adsorption with oppositely charged polycations. The formation of organized polyelectrolyte and enzyme multilayer films of 15-20 nm thickness was demonstrated by quartz crystal microbalance, zeta-potential analysis, and confocal laser scanning microscopy. These biocomposites retained enzymatic catalytic activity, which was proportional to the number of coated enzyme layers. For laccase-fiber composites, around 50% of its initial activity was retained after 2 weeks of storage at 4 degrees C. The synthesis of calcium carbonate microparticles on urease-fiber composites confirmed urease functionality and demonstrated its possible applications. This strategy could be employed to fabricate fiber-based composites with novel biological functions.
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PMID:Cellulose fiber-enzyme composites fabricated through layer-by-layer nanoassembly. 1752 56

The term infection stones refers to calculi that occur following urinary tract infections (UTIs) caused by urease-producing gram-negative organisms. They consist of magnesium ammonium phosphate, carbonate apatite and monoammonium urate. Alkaline urine is most favorable to their formation. Urinary tract obstruction, neurogenic bladder, voiding dysfunction, temporary or indwelling urinary catheters, distal renal tubular acidosis and medullary sponge kidney are considered the main risk factors for developing infection stones. Urinalysis and urine culture are essential for diagnosis. A typical finding on imaging is a moderately radiopaque, staghorn or branched stone. Curative treatment is possible only by eliminating all of the stone fragments and by eradicating UTI. A variety of operative and pharmaceutical approaches is available. Metaphylactic treatment is mandatory to prevent recurrences. The relationship between urinary stones and UTIs is well known and shows two different clinical pictures: (1) stones that develop following UTIs (infection stones) which play a key role in stone pathogenesis, and (2) stones complicated by UTIs (stones with infection) which are metabolic stones that passively trap bacteria from coexistent UTIs and may consist of calcium or non-calcium. This article presents an overview of infection stones, analyzing the epidemiology, composition, pathogenesis, diagnosis, treatment and prevention of this type of calculi.
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PMID:Stones and urinary tract infections. 1772 50

A study for the effect of arsenic (As) contamination on beta-glucosidase, urease, acid-/alkaline-phosphatase, and arylsulphatase activities was conducted in As contaminated soils of West Bengal, India. The studied soils show low total As contents relative to those in other As-contaminated sites. A sequential extraction technique was used to quantify water soluble, exchangeable, carbonate bound, Fe/Mn oxide bound, organic bound, and residual As fractions. Arsenic concentrations in the two most labile fractions (i.e., water soluble and exchangeable fractions) were generally low. The studied enzymes were significantly and negatively correlated with water soluble and exchangeable As forms but did not show any significant correlations with other forms, indicating that water soluble and exchangeable forms exert a strong inhibitory effect on the soil enzyme activities. It is thus suggested that the enzyme activity can be helpful in assessing the effects of As on biochemical quality of soils.
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PMID:Arsenic fractions and enzyme activities in arsenic-contaminated soils by groundwater irrigation in West Bengal. 1791 24

Carbon dioxide occupies a central position in the physiology of Helicobacter pylori owing to its capnophilic nature, the large amounts of carbon dioxide produced by urease-mediated urea hydrolysis, and the constant bicarbonate supply in the stomach. Carbonic anhydrases (CA) catalyze the interconversion of carbon dioxide and bicarbonate and are involved in functions such as CO(2) transport or trapping and pH homeostasis. H. pylori encodes a periplasmic alpha-CA (alpha-CA-HP) and a cytoplasmic beta-CA (beta-CA-HP). Single CA inactivation and double CA inactivation were obtained for five genetic backgrounds, indicating that H. pylori CA are not essential for growth in vitro. Bicarbonate-carbon dioxide exchange rates were measured by nuclear magnetic resonance spectroscopy using lysates of parental strains and CA mutants. Only the mutants defective in the alpha-CA-HP enzyme showed strongly reduced exchange rates. In H. pylori, urease activity is essential for acid resistance in the gastric environment. Urease activity measured using crude cell extracts was not modified by the absence of CA. With intact CA mutant cells incubated in acidic conditions (pH 2.2) in the presence of urea there was a delay in the increase in the pH of the incubation medium, a phenotype most pronounced in the absence of H. pylori alpha-CA. This correlated with a delay in acid activation of the urease as measured by slower ammonia production in whole cells. The role of CA in vivo was examined using the mouse model of infection with two mouse-adapted H. pylori strains, SS1 and X47-2AL. Compared to colonization by the wild-type strain, colonization by X47-2AL single and double CA mutants was strongly reduced. Colonization by SS1 CA mutants was not significantly different from colonization by wild-type strain SS1. However, when mice were infected by SS1 Delta(beta-CA-HP) or by a SS1 double CA mutant, the inflammation scores of the mouse gastric mucosa were strongly reduced. In conclusion, CA contribute to the urease-dependent response to acidity of H. pylori and are required for high-grade inflammation and efficient colonization by some strains.
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PMID:Roles of alpha and beta carbonic anhydrases of Helicobacter pylori in the urease-dependent response to acidity and in colonization of the murine gastric mucosa. 1802 96

Gellan based floating beads of acetohydroxamic acid (AHA) were prepared by the ionotropic gellation method to achieve controlled and sustained drug release for treatment of Helicobacter pylori infection. The prepared beads were evaluated for diameter, surface morphology and encapsulation efficiency. Formulation parameters like concentrations of gellan, chitosan, calcium carbonate and the drug influenced the in vitro drug release characteristics of beads. Drug and polymer interaction studies were carried out using differential scanning calorimetry. Chitosan coating increased encapsulation efficiency of the beads and reduced the initial burst release of the drug from the beads. Kinetic treatment of the drug release data revealed a matrix diffusion mechanism. Prepared floating beads showed good antimicrobial activity (in vitro H. pylori culture) as potent urease inhibitors. In conclusion, an oral dosage form of floating gellan beads containing AHA may form a useful stomach site specific drug delivery system for the treatment of H. pylori infection.
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PMID:Preparation and in vitro characterization of gellan based floating beads of acetohydroxamic acid for eradication of H. pylori. 1816 86

Oyster shell, a byproduct of shellfish-farming in Korea and containing a high amount of CaCO(3), has a high potential to be used as a liming material in agriculture. However, the agricultural utilization of oyster shell is limited due to its high concentration NaCl. The oyster-shell meal collected had a low concentration of water soluble NaCl (mean 2.7 g kg(-1)), which might be a result of stacking the material for 6 months in the open field. It has a very similar liming potential with calcium carbonate, with 3.4 and 3.8 Mg ha(-1) for silt loam (SiL, pH 6.2) and sandy loam (SL, pH 5.8) to bring the soil pH to 6.5, respectively. To determine the effect of crushed oyster-shell meal on improving soil chemical and biological properties and crop plant productivity, oyster-shell meal was applied at rates of 0, 4, 8, 12, and 16 Mg ha(-1) before transplanting Chinese cabbage (Brassica campestris L.) in the two soils mentioned above. Soil pH was significantly increased to 6.9 and 7.4 by 16 Mg ha(-1) shell meal application (4 times higher level than the recommendation) in SiL and SL, respectively, at harvesting stage. The effect of liming was found higher in SL compared to SiL soil, probably due to the different buffering capacity of the two soils. The concentration of NaCl and EC value of soils were found slightly increased with shell meal applications, but no salt damage was observed. Oyster-shell meal application increased soil organic matter, available P, and exchangeable cations concentrations. The improved soil pH and nutrient status significantly increased the microbial biomass C and N concentrations and stimulated soil enzyme activities. With the exception of acid phosphomonoesterase (PMEase) activity, which decreased with increasing soil pH in SL but slightly increased in SiL, the activities of urease and alkali PMEase increased markedly with increasing soil pH by shell meal application. The improved soil chemical and biological properties resulted in increased crop productivity. The highest yield in Chinese cabbage was achieved following the application of 8 Mg ha(-1) oyster-shell meal. Conclusively, crushed oyster shell could be used as an alternative liming material to restore the soil chemical and microbial properties in upland soil and to increase crop productivity.
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PMID:Effects of oyster shell on soil chemical and biological properties and cabbage productivity as a liming materials. 1829 33


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