Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.5.1.5 (urease)
 7,257 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Lenses produce both ammonia and urea, and a previous report suggested that bovine lenses contain a complete urea cycle capable of synthesizing urea from bicarbonate and ammonia. To determine whether lenses produce urea by a complete urea cycle or by arginase alone, intact lenses were cultured with [guanido-14C]-arginine or [14C]-bicarbonate. The [14C]-urea was volatilized to [14C]-CO2 by urease and collected in KOH. The cultured rat, bovine and human lenses produced [14C]-urea from [14C]-arginine; therefore lens arginase activity was also examined in homogenates of rat and human lenses. Rat lens homogenates had constant arginase activity for at least 2 hr at 37 degrees C, and activity increased linearly with the concentration of lens homogenate. Rat lens arginase had an apparent Vmax of approximately 13 nmol/hr/mg lens wet weight in lens homogenates and produced 4-6 nmol urea/hr/mg at 25 mM arginine. Human lens homogenates produced 1-5 nmol/hr/mg. In contrast, neither bovine nor rat lenses cultured with [14C]-bicarbonate produced detectable [14C]-urea, although label was incorporated into unidentified nonvolatile products. These products were shown by ion exchange chromatography and enzymatic assay to contain no detectable arginine or urea. It was concluded that although arginase activity is present, neither rat nor bovine lenses contain significant urea cycle activity. However, it is possible that arginase serves as a source of lens ornithine.
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PMID:Urea formation in rat, bovine, and human lens. 666 5

Seventeen strains of Haemophilus ducreyi were isolated from genital lesions which were negative for syphilis by dark-field examination. Media used for primary isolation at various times during the study were enriched chocolate agar, chocolate agar plus vancomycin (3 microgram/ml), rabbit blood agar plus vancomycin (3 micrograms/ml), fetal bovine serum agar, and fetal bovine serum agar plus vancomycin (3 micrograms/ml). H. ducreyi was isolated on chocolate agar plus vancomycin from 10 of 14 patients found to be positive on one or more media, on rabbit blood agar plus vancomycin from 16 of 17 patients, and on fetal bovine serum agar plus vancomycin from 9 of 11 patients. Sera from six animal species were tested to determine if any would support the growth of H. ducreyi. Horse and rabbit sera supported light growth of some strains. Fetal bovine serum supported good growth of all strains included in the study. Biochemical and physiological tests were done on the 17 isolates, a reference strain of H. ducreyi, and two reference strains of Haemophilus haemoglobinophilus. The results agreed with those reported by Kilian, except that H. ducreyi produced alpha-hemolysis in stabs on rabbit blood agar and was oxidase positive, three strains were urease positive, and CO2 improved the growth of seven strains. All 17 isolates were beta-lactamase positive. The reference strains were beta-lactamase negative.
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PMID:Isolation and identification of Haemophilus ducreyi in a clinical study. 697 72

Color change of pH indicators in broth medium is commonly used to quantify growth of ureaplasmas. These organisms differ from other members of the Mollicutes by their ability to hydrolyze urea to CO2 and NH3. This study describes a method which continuously monitors color change in ureaplasmal broth cultures. Using this technique we found: (i) there was a pH-dependent absorbance at 554 nm in ureaplasmal broth medium containing phenol red, (ii) a sigmoidal-shaped color changing curve (absorbance at 554 nm versus time) was produced by metabolizing organisms whereas a linear curve was generated by antibiotic-inhibited ureaplasmas, and (iii) the minimum cell density which elicited a growth-inhibited color change was 1.25 x 10(4) colony-forming units per ml. Other have shown that apparently dead ureaplasmas can cause a color change in broth media. This color change is probably due to the presence of an active urease. This study graphically and quantitatively assesses growth-inhibited color change.
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PMID:Effect of antibiotics on the dynamics of color change in Ureaplasma urealyticum cultures. 701 6

Five types of commercial laboratory animal bedding were assessed for endogenous ureolytic activity using a sensitive method which measures the rate of evolution of 14C-carbon dioxide from 14C-urea. On a weight basis, the highest levels of urease activity were found in heat-treated hardwood chips and a regular grade of crushed corncobs. A deodorant-treated type of crushed corncobs had a moderately high level of activity, while pelleted corncobs and pelleted alfalfa were almost devoid of urease activity. A heat-stable activator of bacterial urease was found in hardwood chips and crushed corncobs.
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PMID:Ureolytic and urease-activating properties of commercial laboratory animal bedding. 701 65

Urea in dialysate solution was converted by urease into ammonium and bicarbonate. Ammonium and bicarbonate can be removed using a gas absorption unit (e.g. oxygenator) to remove ammonia gas and carbon dioxide. The times for the total ammonium levels in the dialysate to be lowered by 50% were 95 minutes at 25 degree C and 15 minutes at 60 degree C. Increasing the dialysate temperature alone was effective in increasing the removal of ammonium, without the need to add NaOH.
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PMID:Effects of temperature on the removal of urea as ammonia by enzymatic conversion and by gas absorption using an oxygenator. 721 33

The method described is a simple routine assay suited for a short series of serum samples. The time needed for one assay is 2 to 3 min from a stand-by arrangement. The urease is immobilized on controlled pore glass. The beads are placed in the column of an enzyme thermistor unit that is part of a continuous flow system. The heat of reaction when urea is degraded to ammonia and carbon dioxide by immobilized urease is measured and recorded continuously. The technique was investigated as regards to flow dependence, linearity, recovery, precision and some possible interfering substances. The within day precision was 0.8% (C.V.) and the day to day precision, during 56 days, was 3.0% (C.V.). Furthermore, the coefficient of correlation between results obtained with the enzyme thermistor unit and a conventional spectrophotometric method was 0.991.
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PMID:Simple routine assay for serum urea using immobilized urease. 725 85

The nitrogen excretory metabolism of the myxomycete Physarum polycephalum was studied. When cultured in partially defined broth medium or on agar, the principal excretory product was ammonia nitrogen. A small, variable quantity of urea was excreted in liquid culture. No uric acid or other purines were detected in the cultures. When microplasmodia were incubated with sodium [14C]bicarbonate, radioisotope was incorporated into citrulline, arginine, and urea. Incubation with L-[carbamoyl-14C]citrulline yielded labelled arginine, urea, and CO2. Substantial urease activity was found in extracts of the microplasmodia. These results, in conjunction with the lack of an absolute nutritional requirement for arginine, provide evidence that Physarum has a functional arginine biosynthetic pathway, an arginase, and a urease.
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PMID:Arginine synthesis and nitrogen excretion in the myxomycete Physarum polycephalum. 737 43

Urea is extracted from rodent urine-contaminated material with hot acetone. After the extract is evaporated to dryness, aqueous urease solution is added to produce ammonia and carbon dioxide. A blue product, indophenol, is formed by the reaction of ammonia with phenol in the presence of hypochlorite. Absorbance is maximum at 625 nm. Presence of urea is easily detected at 4 microgram. Detection of urine contamination in various materials is compared with detection by the AOAC urease-H2PtCl6 test.
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PMID:Spectrophotometric determination of urea in urine stains on foods and containers. 741 Mar 9

Urease (urea amidohydrolase; EC 3.5.1.5) catalyzes the hydrolysis of urea to yield ammonia and carbamate. The latter compound spontaneously decomposes to yield another molecule of ammonia and carbonic acid. The urease phenotype is widely distributed across the bacterial kingdom, and the gene clusters encoding this enzyme have been cloned from numerous bacterial species. The complete nucleotide sequence, ranging from 5.15 to 6.45 kb, has been determined for five species including Bacillus sp. strain TB-90, Klebsiella aerogenes, Proteus mirabilis, Helicobacter pylori, and Yersinia enterocolitica. Sequences for selected genes have been determined for at least 10 other bacterial species and the jack bean enzyme. Urease synthesis can be nitrogen regulated, urea inducible, or constitutive. The crystal structure of the K. aerogenes enzyme has been determined. When combined with chemical modification studies, biophysical and spectroscopic analyses, site-directed mutagenesis results, and kinetic inhibition experiments, the structure provides important insight into the mechanism of catalysis. Synthesis of active enzyme requires incorporation of both carbon dioxide and nickel ions into the protein. Accessory genes have been shown to be required for activation of urease apoprotein, and roles for the accessory proteins in metallocenter assembly have been proposed. Urease is central to the virulence of P. mirabilis and H. pylori. Urea hydrolysis by P. mirabilis in the urinary tract leads directly to urolithiasis (stone formation) and contributes to the development of acute pyelonephritis. The urease of H. pylori is necessary for colonization of the gastric mucosa in experimental animal models of gastritis and serves as the major antigen and diagnostic marker for gastritis and peptic ulcer disease in humans. In addition, the urease of Y. enterocolitica has been implicated as an arthritogenic factor in the development of infection-induced reactive arthritis. The significant progress in our understanding of the molecular biology of microbial ureases is reviewed.
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PMID:Molecular biology of microbial ureases. 756 14

The urea breath test exploits the urease enzyme of Helicobacter pylori. The hydrolysis of labelled urea releases labelled carbon dioxide that is excreted in the breath. Distribution of urea throughout the stomach prevents sampling errors and allows for semiquantitative assessment of the extent of Helicobacter pylori infection. The urea breath test is very specific and sensitive and can be proposed as the method of choice for detecting Helicobacter pylori infection in ulcer patients before and after eradicating treatment as well as in epidemiological studies.
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PMID:The urea breath test: a non-invasive clinical tool for detecting Helicobacter pylori infection. 757 92


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