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 growth and utilization of nitrogen by intensive Chlorella vulgaris in wastes from production of urea, containing 1300 mg NH4+-N and 4000 mg urea-N/1, was investigated. In these conditions only Chlorella vulgaris AA strain, adapted to high concentrations of ammonia nitrogen, was able to grow. The elimination of nitrogen by continuous cultures was 750 mg urea-N/1 with 5-day flow rate. A considerable part of the urea was hydrolized by urease bacteria and removed in the form of NH3. The effect of intermittent light on the growth of algae was also studied. The better growth than in continuous light, was obtained with alternate one hour periods of light and darkness. Good results were also obtained with the use of 12 hour light and 12 hour darkness.
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PMID:Studies on the purification of wastes from the nitrogen fertilizer industry by intensive algal cultures. IV. growth of Chlorella vulgaris in wastes with high nitrogen content in continuous and intermittent light. 6 57

The regulation of the synthesis of the enzyme urease (urea amido hydrolase E.C. 3.5.1.5.) in Neurospora crassa was investigated. The biosynthesis of urease is repressed by ammonium ions. Under ammonium excess conditions the specific activity of urease decreases from 0.980 to 0.180 mumoles NH3/min/mg protein. By addition of cycloheximide it was shown that ammonia influences the synthesis of this enzyme. Enzyme induction by the substrate could be excluded. Even under the conditions of highest repression a specific activity of urease of 0.180 mumoles NH3/min/mg protein was measured. Possible causes of this constitutive enzyme level are discussed.
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PMID:[Repression of urease biosynthesis in Neurospora crassa by ammonium ions]. 12 30

Urease activity, expressed as mg N-NH3/g dry weight per 30 min at 25 degrees C, was determined in the various parts of the sheep, chicken and pig digestive apparatus. The results were as follows. Sheep: contents--rumen 1.25"/-0.09, reticulum 0.78+/-0.02, omasum 0.44+/-0.02, abomasum 0.002+/-0.001, duodenum 0.003+/-0.001, jejunum 0.18+/-0.03, ileum 0.42+/-0.03, caecum 1.34+/-0.11, colon 0.76+/-0.08, walls-rumen 0.88+/-0.16, reticulum 0.38+/-0.04, omasum 0.11+/-0.02, abomasum 0.01+/-0.002, ileum 0.092+/-0.01, caecum 0.14+/-0.03, colon 0.16+/-0.02. Chicken: contents--jejunum 0.028+/-0.009, ileum 0.043+/-0.013, caecum 0.17+/-0.03, colon and cloaca 0.04+/-0.013. Pigs: contents--jejunum 0.02+/-0.01, ileum 0.14+/-0.08, caecum 0.62+-0.12, colon 0.43+/-0.06. No urease activity was found in the walls of the digestive apparatus or the contents of the duodenum in chickens, or in the walls of the stomach and intestine and the contents of the duodenum in pigs. The results show that urease activity in the digestive apparatus of pigs and poultry is lower than in sheep. Inadequate urease activity in the digestive apparatus explains why chickens and pigs are significantly less capable than ruminants of utilizing urea nitrogen as a substitute for some of the protein in the diet.
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PMID:Urease activity in the contents and tissues of the sheep, pig and chicken gastrointestinal apparatus. 16 May 76

I propose a single, quick method for measuring ammonia in urine and urea in plasma and urine. An ammonia-selective electrodie is used, set up on a microcell, which allows use of small sample volumes. Ammonia is measured directly after partial conversion of ammonium ions to NH3. Urea is measured after its hydrolysis by urease. With urine, the two procedures can be carried out successively in the same cell and on the same sample without changing the procedural conditions. Linear electrode response and accuracy have been checked for concentrations in the expected (normal) range.
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PMID:Determination of ammonia and urea in urine and of urea in blood by use of an ammonia-selective electrode. 49 98

The break-down of benzamide, acetamide, malonamide and allantoin in M. smegmatis was investigated. It has been stated that the uptake of liberated NH3 into the cells, favoured by the presence of an organic acid, occasionally results in a negative NH3 determination. This difficulty can be overcome by an increase of the substrate concentration from 0.8 up to 4 mM. All antoinase activity in mycobacteria can be demonstrated only by an NH3 determination, when all the enzymes necessary for the complete break-down of allantoin are present. Bacteria containing allantoinase but not urease will be negative in this test. Using high amide concentrations (4 mM) some doubtful results concerning the degradation of acetamide, benzamide, nicotinamide and pyrazinamide can be eliminated as could be demonstrated for different strains of mycobacteria.
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PMID:Biochemical background of some enzymatic tests used for the differentiation of mycobacteria. 96 Feb 26

Urease obtained from seeds of Citrullus vulgaris fruits has been studied under three points of view: a) the effect of the urea analogs acetamide and hydroxi-urea on the enzyme kinetic b) the action of the sulfhydryl reagents and the reactivation agents on the enzyme c) the effect of X-rays and the protective action of the cysteamine. The Berthelot reaction for the determination of the liberated NH3 was used enzyme activity. Acetamide has no effect on urease kinetic. Hidroxy-urea which produces a typical green color when it is mixed with the Berthelot reagents at high concentrations, when properly diluted acts a aompetitive inhibitor of urease. Spectrophotometric experiments suggest that the studied urease decomposes hydroxi-urea with liberation of hydroxilamine. The sulphydril reagent, p-hydroxi-mercuribenzoate inhibits the enzime. Cysteine and dithiotreitol reactivate the enzyme activity in no more then 50% even when excess of the substances is used. Probably only in the first step of the urea hydrolysis, the enzyme behaves as a typical SH-enzyme. Urease is very sensitive to X-rays. Cysteamine acts as a protective agent of the enzyme. Dithiotreitol reinforces this protective action. This effect is clearly observed when the Fisbein catalytic method for urease is employed.
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PMID:[Studies on urease from the seeds of Citrullus vulgaris: action of chemical agents and ionizing radiations]. 103 92

The use of an ammonia electrode to quantify ammonia liberated by urease from Helicobacter pylori was assessed in an in vitro study. It was found to be highly sensitive (down to 0.7 ppm NH3) and highly reproducible (coefficient of variation 6.0%). Inhibition of urease by bismuth subsalicylate was evaluated as urease testing is often used to assess clearance of H. pylori in patients treated with bismuth. Concentrations of bismuth subsalicylate up to 5 mg/ml had no inhibitory effect but bismuth subsalicylate at 50 mg/ml resulted in 21% inhibition of the urease activity of an ultrasonicated H. pylori suspension. As a preliminary study, the ammonia electrode was assessed in the endoscopy room in comparison with conventional techniques for H. pylori diagnosis. Antral biopsies from 39 patients attending for routine diagnostic endoscopy were subjected to culture, histology, detection of urease activity with a commercially available slide test (CLO) and with the ammonia electrode to detect ammonia liberated from samples placed in urea solution. 21 patients were positive after 1 h with the ammonia electrode, compared to only 17 with the commercially available slide test. 20 were positive on histology and 19 by culture. All samples positive with the ammonia electrode were either positive by culture or by histology. The ammonia electrode offers a quick, sensitive, quantitative and cheap method for the detection and quantification of H. pylori.
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PMID:Use of an ammonia electrode for rapid quantification of Helicobacter pylori urease: its use in the endoscopy room and in the assessment of urease inhibition by bismuth subsalicylate. 129 2

Hydrolysis of arginine into urea and ornithine (Orn) was observed to take place in several segments of the rat nephron including cortical and medullary pars recta of the proximal tubule (PST) and collecting duct (CD). This work was now extended to the adult mouse and rabbit. Representative nephron segments, obtained by microdissection of collagenase-treated kidneys, were incubated with L-[guanido-14C]arginine (216 microM). Addition of urease produced 14CO2 + 2 NH3 from the newly formed urea released in the incubate. 14CO2 was trapped in KOH and counted. In both species, as well as in the rat, the PST was the site of the highest urea + Orn production, with an intensity increasing from cortex to medulla. For other nephron segments, the pattern was not similar in all species. Significant production of urea + Orn was observed in the proximal convoluted tubule and the medullary thick ascending limb in the rabbit, but not in the CD of either the rabbit or the mouse. The functional significance of this urea + Orn production remains unclear. The total amount of urea generated intrarenally by this reaction does not seem sufficient to play a significant role in the urinary concentrating mechanism. It may be assumed that Orn could be further metabolized to polyamines and play a role in maintaining cell integrity and function in the PST, especially in its medullary part, exposed to hypertonicity and poor oxygen supply.
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PMID:Localization of urea and ornithine production along mouse and rabbit nephrons: functional significance. 144 76

Neomycin (700 mg/8 h), ampicillin (500/6 h) and metronidazole (400 mg/8 h), were compared for their effect, on oral administration for 4 days, in reducing blood ammonia in 27 patients with stable chronic liver disease. It was found that there was 38.2, 38.5 and 8.7 m mol/litre mean reduction in blood ammonia in the neomycin, ampicillin and metronidazole treated groups respectively. The difference in blood ammonia was statistically significant for both neomycin (P = 0.01) and ampicillin (P = 0.03) but there was no significant change after metronidazole treatment (P = 0.6). The total stool enzyme activity at optimum pH was maximally reduced by ampicillin and minimally with metronidazole. The reduction was noted to be 3.51 m mol/1 (P = 0.01), 3.87 m mol/1 (P = 0.08) and 2.8 m mol/1 (P = 0.02) of NH3/g dry weight of stool for neomycin, ampicillin and metronidazole respectively. The main bacterial gut enzymes responsible for ammonia production, urease and protease, were found to be very sensitive to stool pH. At pH 6 their activity was around 20 per cent of what was found in optimum pH of 7.4 and at pH 5 it is only about 8 per cent of optimum activity. None of the three antibacterial agents changed the stool pH significantly. It can be concluded that oral neomycin and ampicillin are superior to oral metronidazole in lowering blood ammonia.
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PMID:Effect of three antibacterial drugs in lowering blood & stool ammonia production in hepatic encephalopathy. 145 72

The high plasma level of citrulline (Cit) is one of a number of abnormalities in the plasma amino acid pattern in chronic renal failure (CRF). Synthesis of arginine (Arg) from citrulline in the kidney is the major source of Arg for the body. In order to evaluate the renal activity of Arg synthesis in CRF, we studied arginine production in proximal convoluted tubules (PCT) isolated from male Sprague-Dawley rats 1 month after 5/6 nephrectomy and from sham-operated rats (n = 6 of each). PCT segments were incubated in a sealed chamber with 50 or 200 microM of [L-ureido 14C]-Cit (simulating in vivo plasma concentrations in healthy rats or rats with CRF, respectively). Arginase and urease were added to the medium to hydrolyze Arg into 14CO2 + NH3. 14CO2 was trapped in KOH and counted. Results showed that: (1) in CRF, Arg production per unit tubular length is increased in proportion to hypertrophy of PCT (x 1.5); (2) in CRF, as in the healthy kidney, Arg production increases with Cit concentration (x 2.5 from Cit 50 to 200 microM). Taking into account the hypertrophy and the elevation in Cit concentration, the increase in Arg production per unit length (x 3.6) is not sufficient to compensate for the reduction in nephron number. Most likely, a greater length of maximal tubule is recruited for renal Arg synthesis in CRF.
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PMID:Arginine synthesis by the proximal convoluted tubule in rats with chronic renal failure. 146 41


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