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)

Helicobacter pylori colonizes the stomach at the interface between the mucus layer and the apical pole of gastric epithelial cells. A number of secreted and shed products from the bacteria, such as proteins and lipopolysaccharide, are likely to have a role in the pathogenesis at the epithelial level. To determine the physiological response of transporting polarized epithelia to released soluble factors from the bacterium, we used the T84 cell line. Monolayers of T84 cells were exposed to soluble extracts from H. pylori. The extracts induced rapid "dome" formation as well as an immediate decrease in transepithelial electrical resistance. Domes are fluid-filled blister-like structures unique to polarized epithelia. Their formation has been linked to sodium-transporting events as well as to diminished adherence of the cells to the substrate. H. pylori-induced dome formation in T84 monolayers was exacerbated by amiloride and inhibited by ouabain. Furthermore, it was associated with changes in the expression of the laminin binding alpha 6 beta 4 integrin and the 67-kDa laminin receptor. Domes formed primarily on laminin-coated filters, rather than on fibronectin or collagen matrices, and their formation was inhibited by preincubating the bacterial extract with soluble laminin. This effect was specific to H. pylori and independent of the urease, vacA, cagA, and Lewis phenotype of the strains. These data indicate that released elements from H. pylori can alter the physiological balance and integrity of the epithelium in the absence of an underlying immune response.
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PMID:Soluble extracts from Helicobacter pylori induce dome formation in polarized intestinal epithelial monolayers in a laminin-dependent manner. 1281 97

Amphiphilic derivatives of sodium alginate, prepared by chemical covalent binding of long alkyl chains onto the polysaccharide backbone via ester functions, form strong hydrogels in aqueous solutions. The shear-thinning and thixotropic behaviors of these hydrogels have been exploited to prepare particles (millimetric beads or microparticles) by dispersion in sodium chloride solutions. This all-aqueous procedure was used for the encapsulation of model proteins, such as bovine serum albumin (BSA) and human hemoglobin (Hb), or of a vaccine protein (Helicobacter pylori (H. pylori) urease). In all cases, the encapsulation yields were very high (70-100%). No release of model proteins was observed in water within several days, in contrast with protein-loaded calcium alginate particles, which exhibit an important release within only a few hours. The controlled release of proteins can, however, be achieved by inducing the dissociation of the physical hydrophobic network. This dissociation has been obtained either by addition of surfactants, acting as disrupting agents of intermolecular hydrophobic junctions, or of esterases such as lipases, which hydrolyze the ester bond between alkyl chains and the polysaccharide backbone. The level of immunization against H. pylori infection in mice, induced by encapsulated urease administrated by either systemic or mucosal routes, was also assessed.
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PMID:Hydrophobically modified alginate hydrogels as protein carriers with specific controlled release properties. 1531 95

Humic substances and three hydrolytic enzymes (beta-glucosidase, phosphatase and urease) were extracted by neutral sodium pyrophosphate from an olive waste (dry olive cake), alone or mixed with municipal biosolids, during a nine month vermicomposting process. Easily degradable compounds decreased during the vermicomposting process because of microbial consumption. When municipal biosolids were added to dry olive cake, microbial activity increased and the amounts of compounds extracted by pyrophosphate were three times lower than olive cake alone. In both instances, beta-glucosidase, phosphatase and urease activities of the organic extracts either increased or remained the same after a nine month period of vermicomposting, thus suggesting that the humus enzyme complexes resisted microbial and earthworm attack. It is known that humus immobilised enzymes also remain active in soil environments, reactivating the nutrient cycles in soil. The use as amendments of vermicomposted olive cake, alone or when mixed with biosolids, could be a good alternative to reactivate the C, P and N-cycles in degraded soils for regeneration purposes.
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PMID:Hydrolytic enzyme activities of extracted humic substances during the vermicomposting of a lignocellulosic olive waste. 1560 91

In this study, flagellin is purified biochemically from eight urease-positive thermophilic camplylobacters (UPTC) isolated from river water, sea water and mussels, and purified also from two isolates of Campylobacter jejuni and C. coli and fractionated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). Results showed that no flagellin components were detected in the two Japanese UPTC isolates (CF89-12 and CF89-14) and the two UPTC NCTC strains (NCTC12893 and NCTC12894). Flagellin components, each consisting of a single peptide, with a heterogeneous molecular mass of approximately 52-63 kDa were demonstrated in the other four UPTC isolates (NCTC12892, NCTC12895, NCTC12896 and NI15F [from Northern Ireland]) and the two Japanese isolates of C. jejuni (JCM2013 and C. coli 27). The approximate molecular mass of flagellin from the flagellin-positive UPTC isolates was smaller than those of C. jejuni and C. coli. Flagella were not detected by electron microscopy in the four flagellin-negative UPTC isolates but they were detected in the four flagellin-positive UPTC isolates and the two isolates of C. jejuni and C. coli. Thus, significant phenotypic diversity for flagellin, which must be due to genotypic variations, was demonstrated among the UPTC isolates.
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PMID:Phenotypic characterisation of flagellin and flagella of urease-positive thermophilic campylobacters. 1564 10

The objective of this study was to determine the specific reference values for urinary calcium/creatinine (UCA/Cr) (mg/mg) in healthy breast-fed newborns, and to evaluate the relationship between UCa/Cr, urinary sodium/creatinine (UNa/Cr), urinary potassium/creatinine (UK/Cr) and UNa/UK ratios in the same group. A total of 88 infants aged between 0-28 days were enrolled in this study. They were divided into two age groups as follows: Group I: < or = 7 days of age; Group 2 infants aged between 8-28 days. Non-fasting spot urine was analyzed for Ca, Na, K and Cr. Significant differences were observed between the two groups in terms of UCa/Cr (0.11+/-0.10 vs 0.27+/-0.23, p<0.001), UNa/Cr (1.29+/-1.63 vs 5.5+/-4.83, p<0.001), and UK/Cr (0.94+/-0.99 vs 2.82+/-2.3, p<0.001). The data showed positive correlation between UCa/Cr and age (r=0.38, p<0.001) as well as between age and UNa/Cr ratio (r=0.68, p=0.0001) and between age and UK/Cr ratio (r=0.57, p<0.0001). Additionally, there was a positive correlation between UNa/UK and age (r=0.40, p=0.001). The UCa/Cr ratio positively correlated with UNa/Cr whereas no correlation was found between UCa/Cr and UNa/Uk ratio. Our data suggest that the healthy neonates differ from the hypercalciuric patients by exhibiting a linear correlation between Na/K and UCa/Cr. As the normal values of UCa/Cr, UNa/Cr, UK/Cr, UNa/UK ratios in the early neonatal period differ from those in the late neonatal period, these differences should be taken into consideration when assessing urinary excretion of these parameters for diagnostic purposes in the early and late newborn periods.
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PMID:The relationship between urinary calcium, sodium, and potassium excretion in full-term healthy newborns. 1588 28

Poly(acrylonitrile-methylmethacrylate-sodium vinylsulfonate) membranes were subjected to seven different chemical modifications and the amount of the newly formed groups was measured for each membrane. Urease was then covalently immobilized onto the modified membranes and the amount of bound protein was determined. The kinetic parameters V(max) and K(m) of the immobilized urease were studied under static and dynamic conditions. Results showed that the rate of the enzyme reaction was higher for the membranes modified with NH(2)OH . H(2)SO(4), NH(2)NH(2) . H(2)SO(4), NaOH + EDA and NaOH + GA + EDA. It was confirmed that the reaction rate, measured under dynamic conditions, was higher than that one determined under static conditions. The influence of Cu(II) ions, as inhibitors, on the enzyme reaction kinetics (V(i) and K(i)) was also investigated. It turned out that the most sensitive membranes towards Cu(II) were those modified with NH(2)NH(2) . H(2)SO(4), NaOH + EDA and H(2)O(2). The results initiated further investigations on the influence of other heavy metal ions (Cd(II), Zn(II), Ni(II) and Pb(II)) over urease bound to a NH(2)OH . H(2)SO(4)-modified membrane. It was found that the inhibition effect of the heavy metal ions over immobilized urease decreases in the order: Cu(II) > Cd(II) > Zn(II) > Ni(II) > Pb(II). [Diagram: see text]
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PMID:Kinetic parameters of urease immobilized on modified acrylonitrile copolymer membranes in the presence and absence of Cu(II) ions. 1589 77

We describe a technique whereby intracellular urease activity can be localized by transmission electron microscopy. The ammonia produced from the enzymatic hydrolysis of urea is first precipitated with sodium tetraphenylboron and then replaced with silver to produce electron-dense silver tetraphenylboron. This direct reaction product deposition procedure was used to demonstrate the presence of membrane-bound urease of Staphylococcus sp. H3-22, a gram-positive ruminal bacterium.
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PMID:Cytochemical Localization of Urease in a Rumen Staphylococcus sp. by Electron Microscopy. 1634 4

Itachi, a soybean (Glycine max [L.] Merr.) variety with 0.2% normal seed urease activity, was recovered from a screen of 6,000 entries in the United States Department of Agriculture soybean germplasm collection. No urease antigen in Itachi seed extracts was detected by double diffusion or by rocket immunoelectrophoresis. Native gels stained for protein or ureolytic activity revealed no detectable urease holoenzyme. An anti-urease antibody affinity column was used to remove all detectable urease activity and antigen from ;wild type' (cv. Prize) seed extracts. Affinity column effluent and nonchromatographed Itachi extracts both lack a species which comigrates with purified urease subunits in sodium dodecylsulfate polyacrylamide gels. Inability to detect urease antigen or urease protein suggests that during development of Itachi seeds there is no synthesis of urease protein or that, at most, its synthesis is 0.2% of wild type (Prize).No urease activity or only traces of urease activity were detected in cotyledons of developing or germinating Itachi seeds. In contrast, callus cultures induced from cotyledon, shoot tip, root, or root tip tissues of Itachi seedlings exhibited ureolytic activity equivalent to that of Prize cultures. Shoot tip cultures of both Prize and Itachi grew with urea as sole nitrogen source. Most or all of the ureolytic activity in crude extracts of Prize and Itachi suspension culture cells is seed-like urease in thermal stability, recognition by antibodies to the seed enzyme, hydroxyurea sensitivity, and nickel requirement for synthesis. It has been reported previously (Polacco, Havir 1979 J Biol Chem 254: 1707-1715; Polacco, Sparks, Jr, Havir 1979 Genet Eng 1: 241-259) that partially purified cell culture urease is identical to seed urease by immunological and electrophoretic criteria. These results suggest that urease is under different developmental controls in the seed and in cell culture.In both Prize and Itachi cultures, utilization of the ureide allantoin, unlike that of urea, is not dependent on nickel. This suggests that ureide catabolism does not require urease.
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PMID:A soybean seed urease-null produces urease in cell culture. 1666 76

Kinetics of urease denaturation by anionic surfactant (sodium n-dodecyl sulphate, SDS) at concentrations below the critical micelle concentration (CMC) is investigated spectrophotometrically at neutral pH and the corresponding two-phase kinetic parameters of the process are estimated from a three-state reversible process using a binomial exponential relation based on the relaxation time method as: Using a prepared computer program, the experimental data are properly fitted into a binomial exponential relation, considering a two-phase denaturation pathway including a kinetically stable folded intermediate formed at SDS concentration of 1.1 mM. Forward and backward rate constants are estimated as: k(1)=0.2141+/-4.5 x 10(-3), k(2)=5.173 x 10(-3)+/-8.3 x 10(-5), k(-1)=0.09432+/-3.6 x 10(-4) and k(-2)=2.079 x 10(-3)+/-5.6 x 10(-5)s(-1) for the proposed mechanism. The rate-limiting step as well as the reaction coordinates in the denaturation mechanism are established. The mechanism involves formation of a kinetically stable folded native like intermediate through the electrostatic interactions. The intermediate was found to be more stable even than the native form (by about 9 kJmol(-1)) and still hexamer, because no loss of amplitude was observed. Electrophoresis experiments on the native and surfactant/urease complexes indicated a higher mobility for the kinetically folded native like intermediate.
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PMID:Denaturation of jack-bean urease by sodium n-dodecyl sulphate: a kinetic study below the critical micelle concentration. 1701 May 76

Urea biosensors based on urease covalently immobilized on to ammonium and hydrogen ion-selective electrodes were included in arrays together with ammonium, potassium, sodium, hydrogen and generic response to alkaline sensors. Response models based on artificial neural network (ANN) and partial least squares (PLS1) were built, tested and compared for the simultaneous determination of urea, ammonium, potassium and sodium. The results show that it is possible to obtain good ANN and PLS calibration models for simultaneous determination of these four species, but with better prediction capability when the ANN are used. The developed bioelectronic tongue was applied to multidetermination in urine samples. The ANN model showed again better agreement with reference methods, allowing a simple direct determination of urea in the real samples without the necessity of eliminating the alkaline interferences, or compensating endogenous ammonium.
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PMID:Potentiometric bioelectronic tongue for the analysis of urea and alkaline ions in clinical samples. 1709 67


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