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 correlation between urease activity of Campylobacter pylori and atrophic gastritis was studied. On the basis of fundamental study on the optimal pH of C. pylori urease activity, urease activity of 38 biopsied specimens were measured under pH 5 condition, and compared with the positive ratio of C. pylori. In this study, sensitivity was 86.7%, and specificity was 87.0%, respectively. Mean urease activity of C. pylori positive specimens was 3.69 mIU/mg protein, and under this condition, C. pylori was likely to produce ammonia of 0.0218 mumole per minute, enough to damage the gastric mucosa. In addition, there was encountered high urease activity in the specimens which showed moderate glandular atrophy and severe mucosal inflammation. In conclusion, urea-urease-NH3 sequence is most likely to have some association with gastric glandular atrophy.
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PMID:[Correlation between Campylobacter pylori and chronic atrophic gastritis]. 225 Mar 90

The biochemical changes induced in the gastric juice by the presence of Campylobacter pylori (CP) were followed up in 151 patients with various gastric and duodenal diseases. The diagnosis of CP infection was made by the urease test. In the presence of CP urea decreased in the gastric juice and ammonia increased. The sialic acid, fucose and hexoses, glucide components of the mucus glycoproteins dissolved in the gastric juice, underwent no change in the presence of CP. The hexosamines in the gastric mucus increased significantly in CP patients. Urease activity is present in the gastric juice even in the absence of CP, probably due to other microorganisms present in the human stomach. This does not exclude the use of the urease test for the diagnosis of CP infection. However the test can only be used in the bioptically removed gastric mucosa samples, not in the gastric juice.
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PMID:Biochemical changes induced by Campylobacter pylori in the gastric juice. 227 Apr 23

Accelerated rates of ammonia production by the renal proximal tubule constitute an important adaptation to chronic renal injury. Although serving to maintain net acid excretion, this augmented production of ammonia per nephron results in increased renal cortical levels of ammonia and contributes to progressive renal injury. Ammonia fosters progressive injury via its ability to modify the third component of complement and initiate alternative complement pathway activity. This interaction of ammonia with complement incites inflammation in models of nonimmune chronic renal disease in the rat and may contribute to tissue injury in pyelonephritis involving urease-positive organisms. The long recognized in vivo association between increased renal ammoniagenesis, renal growth, and progressive injury in several models of renal disease has been advanced by the recent demonstration of ammonia as a direct stimulus to growth of renal tubular epithelium in culture. Additionally, evidence from studies of acute ischemic renal injury suggests a contributory role for ammonia in mediating tissue injury in this model. Elevated renal levels of ammonia, therefore, contribute to tubulointerstitial injury primarily through the proinflammatory and growth-promoting properties of ammonia.
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PMID:Role of ammonia in tubulointerstitial injury. 228 94

Urease of Helicobacter pylori (formerly Campylobacter pylori) is believed to represent a critical virulence determinant for this species. Ammonia generated by hydrolysis of urea may protect the acid-sensitive bacterium as it colonizes human gastric mucosa. An H. pylori strain, cultured from a gastric biopsy of a patient with complaints of abdominal pain and a history of peptic ulcer disease, was isolated on selective medium and cultured in Mueller-Hinton broth supplemented with 4% fetal calf serum. Whole cells were ruptured by French pressure cell lysis, and soluble protein was chromatographed on DEAE-Sepharose, phenyl-Sepharose, Mono-Q, and Superose 6 resins. Purified urease represented 6% of the soluble protein of crude extract, was estimated to have a native molecular size of 550 kilodaltons (kDa), and was composed of two distinct subunits of apparent molecular sizes of 66 and 29.5 kDa. On the basis of subunit size, a 1:1 subunit ratio as measured by scanning densitometry of Coomassie blue-stained sodium dodecyl sulfate-polyacrylamide gels, and estimated native molecular size, the data are consistent with a stoichiometry of (29.5 kDa-66 kDa)6 for the structure of the native enzyme. Km for urea was estimated at 0.2 mM. By N-terminal analysis, the 29.5-kDa subunit of H. pylori urease was found to share significant amino acid sequence similarity with the smallest of three subunits of the Proteus mirabilis and Morganella morganii ureases, as well as to the amino terminus of the unique jack bean subunit. The 66-kDa subunit also shared up to 80% similarity with the largest of three subunits of P. mirabilis, M. morganii, and Klebsiella aerogenes ureases and to internal sequences (amino acids 271 to 285) of the jack bean urease subunit. Thus, the amino acid sequence is conserved among ureases with one, two, and three distinct subunits, suggesting a common ancestral urease gene. Also, urease subunits of M. morganii and jack bean were specifically recognized by antisera raised against the 66-kDa subunit of H. pylori urease, demonstrating that at least some antigenic determinants were conserved among ureases from different species.
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PMID:Purification and N-terminal analysis of urease from Helicobacter pylori. 231 39

Tissue culture cells were exposed to supernatants of Helicobacter pylori for 24 h at 37 degrees C in the presence of various quantities of urea. In the normal human stomach the concentration of urea is less than or equal to 4 mmol/l, and in the presence of this low concentration up to 10% of Vero cells showed intracellular vacuolization. In the presence of 7.5 mmol/l urea, 25% of the cells showed vacuolization. With 30 mmol/l urea, the final pH was 7.6, indicating that vacuolization was not due to change of pH. The first report of vacuolization of tissue culture cells by H. pylori was in a system without added urea but with concentrated bacterial supernatant; 30% of H. pylori strains demonstrated a cytotoxic effect. In those experiments fetal calf serum was used; it contains 6 mmol/l urea but was used at a concentration of 10%. A urease inhibitor, acetohydroxamic acid, caused a 75% drop in the number of cells showing vacuolization, and ammonia caused vacuolization. Thus the urea of H. pylori probably causes this vacuolization.
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PMID:Intracellular vacuolization caused by the urease of Helicobacter pylori. 234 8

Colonization of the stomach with Helicobacter (Campylobacter) pylori is common in patients with duodenal ulcer disease, which is known for its high acid secretion. Although the bacterium is usually isolated by culture of a gastric biopsy specimen, viable organisms may sometimes be found in the acidic gastric juice. It was postulated that urease, by generating ammonia, protected H. pylori from acid. To test this hypothesis, the pH susceptibility of H. pylori, Proteus mirabilis, and the urease-negative Campylobacter jejuni was examined in the presence and absence of urea. It was found that without urea the three bacteria were all highly susceptible to acid. In striking contrast, the addition of 5 mmol/L of urea completely protected H. pylori but not P. mirabilis or C. jejuni from pH values as low as 1.5. Furthermore, the protective effect of urea on H. pylori was found with urea concentrations as low as 0.05 mmol/L. It is concluded that the high urease activity of H. pylori enables it to survive in gastric acid.
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PMID:Urea protects Helicobacter (Campylobacter) pylori from the bactericidal effect of acid. 237 75

Enzyme sensors for urea and creatinine were developed by coupling an ammonia gas-diffusion electrode with triacetate cellulose membranes entrapping urease or creatinine deiminase enzymes. Satisfactory results were obtained by using these sensors both in standard solutions and in authentic biological matrices.
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PMID:Suitable potentiometric enzyme sensors for urea and creatinine. 239 88

A quantitative capillary tube enzyme immunoassay (CTEIA) method for the determination of human urinary chorionic gonadotropin (hCG) has been developed. The method utilizes an antibody-coated capillary tube through which the test fluid is passed and a urease-labelled second antibody in an immunometric format. Any hCG in the test solution is 'captured' by the immobilized antibody which is hybridoma derived and specific for the beta-subunit of hCG. The second hCG-specific antibody, conjugated to the enzyme urease, is used to detect the captured hCG on the internal surface of the capillary tube. The amount of urease bound to the surface is determined by the introduction of a substrate solution containing urea and the pH indicator bromothymol blue. The rate of colour change, from yellow to blue, caused by the release of ammonia from urea by urease, is determined in a spectrophotometer using a cell holder adapted to accommodate capillary tubes. The initial rate of absorbance change is directly proportional to the concentration of hCG in the sample in the range 0-100 mIU/ml. The test can detect concentrations of hCG as low as 10 mIU/ml in a total elapsed time of 5 min.
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PMID:A rapid quantitative capillary tube enzyme immunoassay for human chorionic gonadotropin in urine. 243 10

A method to detect the presence of Campylobacter pyloridis in dyspeptic patients is described. The test procedure involves placing a gastric pinch biopsy into a small amount of a solution containing urea and a pH indicator in the well of a microtiter tray. The method depends on the ability of C. pyloridis to hydrolyse urea and release an alkaline product (ammonia). The "microtiter biopsy urease test" is 100% specific for C. pyloridis and has a 91% sensitivity after 18 h reaction time. Seventy-five percent of positive biopsies had a reaction time of less than 1 h. The test may be used to predict the presence of antral gastritis; as well as marking the presence of the bacterium; with a positive predictive value of 96% and a negative predictive value of 73%. There was a positive correlation between the biopsy urease test results and the grades of both chronic and active antral gastritis. This test is simple and can be performed in the endoscopy clinic as the formulation of the reagent obviates the need for aseptic techniques.
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PMID:Campylobacter pyloridis gastritis I: Detection of urease as a marker of bacterial colonization and gastritis. 243 70

Artificial cells containing glucose dehydrogenase (EC 1.1.1.47), leucine dehydrogenase (EC 1.4.1.9), urease (EC 3.5.1.5), and dextran-NAD+ were prepared. Ammonia or urea could be converted into L-leucine, L-valine, and L-isoleucine with artificial cells. Low-specific-activity glucose dehydrogenase could effectively regenerate dextran-NADH, which was recycled at a rate of 0.4 to 0.5 cycle per minute under reaction conditions. The effects of ammonium salts and urea on the conversion rate for the leucine dehydrogenase multienzyme system were also studied. The relative activities in ammonium salts solutions were 40 to 70% of those in urea solutions.
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PMID:Conversion of ammonia or urea into L-leucine, L-valine, and L-isoleucine using artificial cells containing an immobilized multienzyme system and dextran-NAD+. Glucose dehydrogenase for co-factor recycling. 245 27


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