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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)

Seventeen strains of the new species Bacillus azotoformans were isolated by enrichment culture in peptone broth inoculated with pasteurized soil and then incubated under N2O at 32 degrees C. The bacterium is a Gram-negative rod, motile with peritrichous flagella, which produces oval spores without exosporia in swollen sporangia. However, the cells have thick walls, mesosomes, and persistent septa characteristic of Gram-positive bacteria. The bacterium lacks fermentative activity, does not attack carbohydrates, has complex growth requirements, and will grow anaerobically only if one of the following electron acceptors is present: NO3-, NO2-, N2O, S4O6--, or fumarate. Nitrate, nitrite, and nitrous oxide are denitrified with the production of N2. The microorganism is mesophilic, gives a positive oxidase reaction, synthesizes a type c cytochrome, and does not hydrolyse gelatin, starch, or "Tween 80." Poly-beta-hydroxybutyric acid is snythesized when the bacterium is grown in a medium containing DL-3-hydroxybutyrate. The following enzymes are present: nitrate reductase A, respiratory nitrite reductase, tetrathionate and fumarate reductases, and L-glutamate dehydrogenase. The following enzymes are absent: thiosulfate reductase, urease, lecithinase, arginine dihydrolase, phenylalanine deaminase, and catalase. For the 17 strains, the mean value of the G = C percent of the DNA is 39.8 +/- 1.2. All the strains are highly similar.
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PMID:[Morphological, physiological and taxonomic studies of Bacillus azotoformans]. 65 12

The described bacterium was isolated by enrichment culture in peptone broth inoculated with garden soil, pasteurized and then put to incubate under N2O at 32 degrees. It is a Gram-negative rod, motile with peritrichous flagella, and producing oval spores without exosporium in swollen sporangia. However, cells have the thick walls, mesosomes and persistant septa characteristic of Gram-positive bacteria. It lacks fermentative activity, does not attack carbohydrates, has complex growth requirements, and will grow anaerobically only if one of the following electron acceptors is present: NO3, NO2, N2O, S4O6, and fumarate. Nitrate, nitrite, and nitrous oxide are denitrified with production of N2. The microorganism is mesophilic, gives a positive oxidase reaction, synthesizes a type of c cytochrome, and does not hydrolyse gelatin, starch nor "Tween 80". The following enzymes are present: nitrate reductase A, respiratory nitrite reductase, tetrathionate and fumarate reductases, L-glutamate dehydrogenase, and superoxide dismutase. The following enzymes are absent: thiosulfate reductase, urease, lecithinase, arginine dihydrolase, L-alanine dehydrogenase, phenylalanine desaminase, and catalase. The GC% of its DNA is 39. The bacterium described can be considered to be a new species. We propose the name Bacillus azotoformans n. sp.
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PMID:[A new, sporulating, denitrifying, mesophilic bacterium: Bacillus azotoformans N. SP. (author's transl)]. 102 Aug 72

The toxicity of Cu, Ni and Fe individually, as well as in combination (Cu + Ni, Cu + Fe, Ni + Fe), on growth-rate depression, uptake of NO3- and NH4+, photosynthesis, nitrate reductase and urease activity of Chlorella vulgaris has been studied. All the test metals when used individually showed pronounced toxicity on all the parameters studied. However, their interactive effect was mostly antagonistic except for Cu + Ni (synergism). Pre-addition of Fe offered more protection to the cells against copper and nickel toxicity. The data of statistical analysis reconfirmed that 14CO2 uptake is the most sensitive parameter (significant at P less than 0.005, both for time and treatment) than others in metal toxicity assessment. However, these results suggest further that exposure time and sequence of metal addition are very important in biomonitoring of heavy metal toxicity.
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PMID:Impact of bimetallic combinations of Cu, Ni and Fe on growth rate, uptake of nitrate and ammonium, 14CO2 fixation, nitrate reductase and urease activity of Chlorella vulgaris. 216 14

Sonication of Ureaplasma urealyticum cells grown in a dialysate growth medium effectively separated the cytoplasmic fraction from the membrane fraction, with both fractions relatively free from exogenous contaminating proteins. The urease activity was associated with the cytoplasmic fraction, and the ureaplasmal urease exhibited a specific activity higher than that of crystalline jack bean urease. The enzymatic activity of the ureaplasmal enzyme was optimum at pH 7.5 and was resistant to the chelating agents EDTA and sodium citrate. Sulfhydryl-blocking agents such as HgCl2 and Pb(NO3)2 inhibited the ureaplasmal urease, which was also shown to be particularly sensitive to flurofamide and, to a much lesser extent, to acetohydroxamic acid. Electrophoretic analysis of the proteins of the ureaplasmal cell fractions combined with Western immunoblot with an antiserum to the ureaplasmal urease indicated that the urease constitutes a major component of the cytoplasm and is composed of several 70-kilodalton polypeptides.
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PMID:Characteristics of Ureaplasma urealyticum urease. 313 6

We have shown that the low histidase activity found in anaerobic, nitrogen-limited cultures of Klebsiella pneumoniae is due to repression of the right-hand hut operon. In addition, we have examined the effects of NO3- on the aerobic and anaerobic expression of catabolite- and NH4+-repressible enzymes in this organism. NO3- permitted anaerobic growth of K. pneumoniae in minimal medium containing histidine as the sole carbon source, and histidase and succinate dehydrogenase were derepressed during anaerobic growth in histidine/NO3- medium. Use of sucrose rather than histidine as the carbon source reversed the effects of NO3- and repressed histidase and succinate dehydrogenase activities. Anaerobic growth in sucrose/NO3- medium also uncoupled the expression of urease and glutamine synthetase.
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PMID:Effects of anaerobiosis and nitrate on the expression of succinate dehydrogenase and enzymes associated with nitrogen metabolism in Klebsiella pneumoniae. 612 18

Biotransformation of NO, nitrite and nitrate was investigated in rats and mice in a 15NO inhalation experiment and intraperitoneal injection experiments of 15N-nitrite and 15N-nitrate, and the following results were obtained: (1) Rats were forced to inhale 15NO (145 ppm, 123 minutes) or were given an intraperitoneal injection of 15N-nitrite (2 mg animal-1 as 15N) or 15N-nitrate (2mg animal-1 as 15N), and determination of 15N recovery in urine was made up to 48 h later. The results were 55, 53 and 78% of the inhaled or injected 15N, respectively. (2) 15N-nitrate in the urine was converted into a 6-nitro derivative of 3,4-xylenol and its identification and quantitative determination were made by the GC-MS method. As to 15N-urea in the urine, identification and quantitative determination were made by the urease method. 15N was present in the urine of rats after 15NO inhalation in the form of NO3- and urea. 75 and 24% respectively. In the urine of rats injected with 15N-nitrite, about 20% of unidentified 15N-compounds not discovered in the inhalation experiment was found. The content of 15N-urea in the urine after injection with 15N-nitrate was lower than that after injection with 15N-nitrite. (3) When 15N-nitrite (0.617 mg animal-1 as 15N) was injected intraperitoneally in mice, 60.7, 7.8 and 0.3% of the injected 15N were found in the urine, feces and exhaled gas (NO, NO2 and NH3 in the gas were caught) up to 48 h after injection respectively, and 1.6% was found in the body 48 h after injection, but the remaining 30% of 15N could not be recovered.
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PMID:Biotransformation of nitric oxide, nitrite and nitrate. 662 3

The biosensor with urease entrapped in PVC layer at the surface of pH-sensitive iridium oxide electrode was applied for testing of mercury and other metal ions inhibition on enzymatic reaction. The calculation of inhibition effect was based on the measurement of initial rate of decrease of biosensor potential (proportional to the initial rate of enzymatic reaction) after addition of substrate after inhibition step. Some differences of inhibition extent were observed for various mercury forms (Hg(NO3)2, HgCl2, PhHgCl and Hg2(NO3)2) as well as for other heavy metal ions investigated as potential interferents. Because the method was not specific, it was applied for the determination of total inhibition effect caused by heavy metal ions in water samples. In the case of most cations tested the total recovery of enzyme activity was possible using Tris buffer solution with EDTA and thioacetamide after less than 10 min regeneration time.
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PMID:Inhibitive determination of mercury and other metal ions by potentiometric urea biosensor. 1121 29

Soil available N, NH4(+)-N and NO3(-)-N contents and soil urease activity were measured after application of rave earth elements(REEs). The results showed that the contents of soil available N and NH4(+)-N were affected by application of REEs, being significantly differed from those in the control when the dosage was higher than 5 mg.kg-1 dry soil. However, soil NO3(-)-N content in treated plots did not differed from that in the control. No observed effect concentration (NOEC) for the potential influence of REEs on the chemical transformation and availability of soil available nitrogen was found to be 5 mg.kg-1 dry soil. The decrease of soil available N concentration was found closely correlated to the inhibition of soil urease activity (R2 = 0.87). It was suggested that the inhibition effect of REEs on the enzymatic nitrogen mineralization should be one of the major causes for the decline of soil available nitrogen concentration. The decrease of available nitrogen concentration occurred shortly after REEs application, indicating that there should be a self-regulation process to maintain the available nitrogen concentration in soil.
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PMID:[Influence of rare earth elements on chemical transformation of nitrogen in agricultural soil]. 1175 79

This study investigated whether the serum nitrite concentration reflects Helicobacter pylori-induced inflammation and atrophic changes of gastric mucosa. Ninety-seven patients underwent biopsy of both antrum and fundus. Samples were analyzed by the rapid urease test and histopathological examination according to the updated Sydney system. Fasting serum samples from each subject were analyzed for specific IgG Helicobacter pylori antibodies, pepsinogen I and II concentrations, and NO2-/NO3- content. Eleven patients had H. pylori eradicated with proton pump-based triple therapy. There was a strong positive correlation between the Helicobacter pylori density in the gastric mucosa and the serum nitrite concentration, but a negative correlation existed between the atrophic grade of the gastric mucosa and both serum nitrite concentration and Helicobacter pylori density in the gastric mucosa. Serum nitrite concentrations decreased significantly after successful eradication of Helicobacter pylori. Therefore, serum nitrite concentration may be a useful marker for oxidative DNA damage and apoptosis associated with Helicobacter pylori infection.
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PMID:Does serum nitrite concentration reflect gastric carcinogenesis in Japanese Helicobacter pylori-infected patients? 1183 8

With an aerobic incubation test, this paper studied the response of soil urease, nitrate reductase, nitrite reductase, and hydroxylamine reductase to urease inhibitor hydroquinone (HQ) applied in combination with nitrification inhibitor encapsulated calcium carbide (HQ + ECC) or dicyandiamide (HQ + DCD). The results showed that HQ + DCD could inhibit urease activity and increase activities of nitrate reductase, nitrite reductase, and hydroxylamine reductase significantly in comparison with CK, HQ and HQ + ECC. Under the condition of our test, there existed a significant relationship between soil urease, nitrate reductase, nitrite reductase, and hydroxylamine reductase activities and soil NH4+ and NO3- contents, NH3 volatilization and N2O emission rate, and regression analysis indicated that there were significantly positive relationships between soil urease, nitrite reductase and hydroxylamine reductase activities.
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PMID:[Response of N transformation related soil enzyme activities to inhibitor applications]. 1256 Nov 70


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