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)

Kidney stones have an overall incidence of two to three percent in western countries. In many patients, the disease process is difficult to control and recurrence rates are high: 20 to 50 percent over the subsequent ten years. The pathogenesis and standard methods of treatment for the five major types of stones (i.e., calcium oxalate, struvite, calcium phosphate, uric acid, and cystine) are reviewed. Three new drugs are reviewed in the context of their roles in the selective treatment of kidney stones. Cellulose sodium phosphate (Calcibind) is a nonabsorbable ion-exchange resin with a limited indication for the treatment of calcium stones associated with absorptive hypercalciuria Type I. Acetohydroxamic acid (Lithostat) is an urease-inhibitor that is indicated as adjunctive therapy in patients with chronic urea-splitting urinary tract infections and struvite stones. Potassium citrate (Urocit) is an investigational agent that has clinical efficacy in patients with calcium oxalate and calcium phosphate stones who are hypocitraturic. In addition, potassium citrate is an alkalinizing agent that can be used in patients with uric acid stones.
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PMID:New drug therapy for kidney stones: a review of cellulose sodium phosphate, acetohydroxamic acid, and potassium citrate. 389 14

To study whether human urine contains inhibitors against urease-induced crystallization, Jackbean urease and human urine, in amounts small enough (0.5 to 10 per cent) not to influence the ion concentration, buffering capacity or pH, were added to synthetic urine. The ammonia production and alkalinization that followed were independent of the amounts of human urine added. The addition of human urine gave a dose-related decrease in the amount of calcium phosphate and struvite precipitated on glass rods immersed in the synthetic urine, however. Addition of only 0.5 per cent human urine gave a reproducible decrease and when 10 per cent human urine was added to the synthetic urine the precipitation of calcium phosphate was reduced by 50 per cent and that of struvite by 75 per cent. The results thus indicate that human urine contains components with the ability to reduce the urease-induced crystallization.
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PMID:The inhibitory effect of human urine on urease-induced crystallization in vitro. 394 82

The urease-induced crystallization of magnesium ammonium phosphate and calcium phosphate was studied at different alkalinization degrees by incubating synthetic urine with increasing Jack Bean urease concentrations. The crystallization was studied as precipitation on glass rods immersed in synthetic urine. The calcium phosphate precipitation on the glass rods occurred when the pH reached 6.8. Magnesium ammonium phosphate precipitation occurred when the pH reached 7.0. The maximal crystallization occurred at a pH between 7.5 and 8.0; at higher pHs the precipitation was considerably lower. The possible mechanisms and clinical implications behind this narrow pH optimum for urease-induced crystallization, which also have important implications for future experimental studies, are discussed.
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PMID:Urease-induced crystallization in synthetic urine. 397 8

A combination of enzyme kinetic studies and active enzyme gel chromatography on Sepharose CL-6B was used to explore conformational changes of the enzyme urease as it catalyzes the hydrolysis of urea in 0.7 M phosphate buffer, pH 7.0, at 20 degrees C. It is shown that elucidation of this system is only possible by studying the effects of inert space-filling macromolecules (ovalbumin and bovine serum albumin) on enzymatic behavior. The resulting increases in reaction velocity are interpreted in terms of composition-dependent activity coefficients assessed on a statistical mechanical basis of excluded volume. The results are first considered in terms of two extreme models; one involving a volume change on the isomerization of the enzyme-substrate complex to its activated state, and the other an isomeric expansion of the enzyme-substrate complex to an inactive form. Although both extreme models provide satisfactory descriptions of the kinetic results, they lead to unrealistic values for the radii of the various states of the enzyme-substrate complex. It is concluded, therefore, that the two isomeric transitions act conjointly, a result in conformity with the previously postulated conformational change associated with formation of the activated enzyme-substrate complex [L. W. Nichol, M. J. Sculley, L. D. Ward, and D. J. Winzor (1983) Arch. Biochem. Biophys. 222, 574-581], and also with the well-established action of the substrate, urea, as an unfolding agent of proteins.
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PMID:Effect of thermodynamic nonideality in kinetic studies: evidence for reversible unfolding of urease during urea hydrolysis. 400 54

Certain dental plaques, removed from sites of gingival and periodontal pathology in mentally retarded, institutionalized individuals, when incubated in phosphate buffer with Achilles tendon collagen, gave rise to an increase in ninhydrin-positive material. These plaques, while showing great variability, released significantly more ninhydrin-positive material per milligram of plaque (wet weight) than did either the endogenous or heat-treated controls. Certain plaques could also break down soluble, tritiated, labeled collagen isolated from the calvaria of chicken embryos. Bacteroides melaninogenicus and Clostridia histolyticum were found in plaques by either fluorescent antibody or cultural methods. C. histolyticum, when detected, accounted for about 0.01 to 0.1% of the bacteria in plaque. A conspicuous isolate from some plaques was a Bacillus species which rapidly liquefied gelatin. Cell-free supernatants of this organism were able to degrade about 50 to 70% of the soluble collagen when incubated at 36 C. C. histolyticum ATCC 8034 caused an 80% degradation of the collagen under the same conditions of incubation. The Bacillus strains were facultative, could ferment glucose, reduced nitrate to nitrite, and were catalase, indole, and urease negative. The limited taxonomic information for the isolates is compatible with the description given for Bacillus cereus.
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PMID:Collagenolytic activity of dental plaque associated with periodontal pathology. 436 Dec 94

1. Yeast alcohol dehydrogenase was used to determine ethanol in the portal and hepatic veins and in the contents of the alimentary canal of rats given a diet free from ethanol. Measurable amounts of a substance behaving like ethanol were found. Its rate of interaction with yeast alcohol dehydrogenase and its volatility indicate that the substance measured was in fact ethanol. 2. The mean alcohol concentration in the portal blood of normal rats was 0.045mm. In the hepatic vein, inferior vena cava and aorta it was about 15 times lower. 3. The contents of all sections of the alimentary canal contained measurable amounts of ethanol. The highest values (average 3.7mm) were found in the stomach. 4. Infusion of pyrazole (an inhibitor of alcohol dehydrogenase) raised the alcohol concentration in the portal vein 10-fold and almost removed the difference between portal and hepatic venous blood. 5. Addition of antibiotics to the food diminished the ethanol concentration of the portal blood to less than one-quarter and that of the stomach contents to less than one-fortieth. 6. The concentration of alcohol in the alimentary canal and in the portal blood of germ-free rats was much decreased, to less than one-tenth in the alimentary canal and to one-third in the portal blood, but detectable quantities remained. These are likely to arise from acetaldehyde formed by the normal pathways of degradation of threonine, deoxyribose phosphate and beta-alanine. 7. The results indicate that significant amounts of alcohol are normally formed in the gastro-intestinal tract. The alcohol is absorbed into the circulation and almost quantitatively removed by the liver. Thus the function, or a major function, of liver alcohol dehydrogenase is the detoxication of ethanol normally present. 8. The alcohol concentration in the stomach of alloxan-diabetic rats was increased about 8-fold. 9. The activity of liver alcohol dehydrogenase is generally lower in carnivores than in herbivores and omnivores, but there is no strict parallelism between the capacity of liver alcohol dehydrogenase and dietary habit. 10. The activity of alcohol dehydrogenase of gastric mucosa was much decreased in two out of the three germ-free rats tested. This is taken to indicate that the enzyme, like gastric urease, may be of microbial origin. 11. When the body was flooded with ethanol by the addition of 10% ethanol to the drinking water the alcohol concentration in the portal vein rose to 15mm and only a few percent of the incoming ethanol was cleared by the liver.
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PMID:The physiological role of liver alcohol dehydrogenase. 548 98

Escherichia coli with no demonstrable urease activity was inoculated into filter sterilized urine obtained from a healthy volunteer subject with no history of stone disease and then incubated at 37 degrees C. Bacteria were recovered at intervals between 1 and 10 days. Urinary pH was stable as compared to control urines and spontaneous crystal precipitation was not noted in controls. Recovered organisms were analyzed by x-ray powder diffractometry. An uncharacterized mineral phase (UMP) was first evident after 6 days. Calcium phosphate in the form of brushite and hydroxyapatite was apparent at 7 and 10 days respectively. This suggests a role for bacteria in calcium phosphate crystal formation in urine apart from urease activity and may contribute to the calcium phosphate component of urinary calculi.
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PMID:Calcium phosphate crystal formation in Escherichia coli from human urine: an in vitro study. 627 77

The paper deals with kinetics of the urea hydrolysis by microbial-origin urease dissolved and immobilized on the organic silica surface. It is shown that hydrolysis kinetics for soluble urease is described by the Michaelis-Menten equation until the concentration of urea reaches 1 M. Two fractions differing in the Michaelis constant are revealed for silochrome immobilized urease. The rate of urea hydrolysis by native and immobilized urease was studied depending on the pH value in presence of the substrate in the 1 M and 5 mM concentration. The hydrolysis rate of 1 M urea in the buffer-free solution by silochrome-immobilized urease is practically independent of pH within 4.5-6.5. Application of a 2.5 mM phosphate-citrate buffer as a solvent causes an increase in the hydrolysis rate within this pH range. For a soluble urease the 1 M urea hydrolysis rate dependence on pH is ordinary at pH 5.8-6.0. If the substrate concentration is 5 mM, the pH-dependences for the rate of the urea hydrolysis by silochrome- and aerosil-immobilized urease are close and at pH above 6.0 coincide with those for a soluble enzyme. The found differences in the properties of soluble and immobilized ureases are explained by the substrate and reaction products diffusion.
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PMID:[Properties of urease immobilized on the functional organic silica surface]. 628 52

An ELISA utilising a urease-antibody conjugate specific to chicken IgG was examined as an alternative to the serum agglutination and the haemagglutination inhibition tests in the diagnosis of Mycoplasma gallisepticum and M. synoviae infections in poultry. Use of a urease conjugate allowed the serum reactions to be appraised without the need for expensive photometric equipment. Non-specific binding of conjugate to antigen was eliminated by treatment of antigen coated microplates with 10% foetal calf serum in phosphate buffered saline. Some chicken serums produced non-specific reactions. These reactions were reduced without any loss of test sensitivity by making the initial 1:5 dilution of chicken serum in whole sheep serum rather than diluting buffer. Tests on serums from experimentally infected chickens showed that the urease ELISA was specific, and was as sensitive as the serum agglutination test but more sensitive than the haemagglutination inhibition test.
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PMID:A urease-ELISA for the detection of mycoplasma infections in poultry. 637 68

Ingestible adsorbents for the removal of uremic metabolites are being investigated as adjunctive therapy in the treatment of chronic uremia. In particular, a microcapsule product containing urease and zirconium phosphate (UZP) has been investigated for removing urea. A dog model, simulating chronic uremia, was developed to investigate: (1) the concentration of various nitrogenous metabolites (urea, creatinine, and uric acid) in the GI tract, (2) flux rates of H2O and various nitrogenous metabolites in the GI tract, and (3) the efficacy of the microcapsule product. The results of these perfusion studies suggest that urea and creatinine can be removed from the GI tract via ingestible adsorbents. In addition, the model may be useful in investigating suspect uremic toxins, e.g., guanidinosuccinic acid (GSA). The reduction of blood urea nitrogen levels in the dog model when the animal was fed the microcapsule product was limited by the capacity of the zirconium phosphate to bind ammonium ion. Preliminary clinical studies with the microcapsule product indicate that it may be of potential adjunctive therapy in patients suffering from chronic renal failure.
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PMID:An orally administered microcapsule system for treating chronic renal failure patients. 652 33


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