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 product of the selA gene, selenocysteine synthase, is a pyridoxal 5-phosphate-containing enzyme which catalyzes the conversion of seryl-tRNA(Sec UCA) into selenocysteyl-tRNA(Sec UCA). Reduction of the aldimine group of pyridoxal 5-phosphate inactivates the enzyme. When reacted with seryl-tRNA(Sec UCA) as sole substrate, pyruvate (and possibly also ammonia) is released; in the presence of a high concentration of potassium borohydride, alanyl-tRNA(Sec UCA) is formed from seryl-tRNA(Sec UCA). These results support the notion that the formyl group of pyridoxal phosphate forms a Schiff base with the alpha-amino group of L-serine with the subsequent 2,3-elimination of a water molecule and the generation of an aminoacrylyl-tRNA(Sec UCA) intermediate. ATP is not required for this reaction step, but it is necessary for the conversion of aminoacrylyl-tRNA into selenocysteyl-tRNA(Sec UCA) which, in addition, requires the SELD protein and reduced selenium. Selenocysteine synthase forms a stable complex with seryl-tRNA(Sec UCA) with one tRNA molecule bound per two 50-kDa monomers. The enzyme does not interact with serine-inserting tRNA species. Taken together, the results show that biosynthesis of selenocysteine takes place in the enzyme-bound state and involves the dehydration of L-serine esterified to tRNA in a first step formally followed by the 2,3-addition of HSe- which is provided by the SELD protein in an ATP-dependent reaction in the form of a reactive selenium donor molecule.
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PMID:Selenocysteine synthase from Escherichia coli. Analysis of the reaction sequence. 200 85

Using a protein isolated from soy, a dynamic water adsorption method was developed and the data were compared with those obtained from a static gravimetric procedure. Both methods gave comparable results, showing that Type II isotherms with considerable hysteresis were obtained. However, the dynamic procedure was preferred since it provided data rapidly and used significantly less material. Using the dynamic method, water adsorption isotherms at 25 degrees C were also determined for four biologically active proteins: alpha-amylase, beta-glucuronidase, lipase, and urease. BET (Brunauer, Emmet, and Teller) parameters were calculated and the specific surface areas for the native, biologically active proteins were found to be similar, 238.4 +/- 20.2 m2/g. On the other hand, the specific surface area for the denatured soy protein isolate was 144.6 m2/g. Nevertheless, the heat of absorbance for all of the proteins examined was similar, suggesting that they have comparable degrees of hydrophilicity.
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PMID:Water vapor adsorption and desorption isotherms of biologically active proteins. 202 66

Gastric urease was studied isotopically in 230 patients with biopsy-proven normal mucosa or chronic gastritis, including 59 patients with ulcer disease. Carbon-14-urea was given in 25 ml of water without substrate carrier or nutrient-dense meal, and breath samples were collected over a 60-min period. The amount of 14CO2 excreted at 10 min was independent of the rate of gastric emptying and was not quantitatively influenced by the buccal urease activity. The 10-min 14CO2 values discriminated well between Helicobacter pylori positive and negative patients (94% sensitivity, 89% specificity) and correlated with the number of organisms assessed by histology. The test was a good predictor of chronic gastritis (95% sensitivity and 96% specificity), and a quantitative relationship was observed between 14CO2 values and the severity and activity of the gastritis. In H. pylori positive patients, breath 14CO2 was found to be similar in patients with and without ulcer disease, suggesting that the number of bacteria is not a determining factor for the onset of ulceration.
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PMID:Quantification of Helicobacter pylori infection in gastritis and ulcer disease using a simple and rapid carbon-14-urea breath test. 204 33

Synthetic membranes containing 10% acrylamide units were subjected to activation with formaldehyde at pH 7.5 and 45 degrees C. Trypsin, invertase, and urease were bound to this activated membrane and the kinetic properties of immobilized enzymes were studied. The permeability of the membrane for distilled water manifests certain differences depending on the enzyme bound. The membranes with immobilized enzymes stored at 4 degrees C in a moist state showed no change in their activity for 6 months. The membrane with immobilized invertase has preserved its activity even after 20 operations with 2% sucrose solution at 25 degrees C. The proposed method of binding enzymes to synthetic membranes containing acrylamide groups, through the introduction of N-hydroxymethyl groups, possesses several advantages with respect to the activation of the membrane in a one-step reaction with cheap and accessible reagent, high operative stability of the immobilized enzymes, no danger of bacterial rotting, and long shelf life of the membrane.
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PMID:Covalent binding of enzymes to synthetic membranes containing acrylamide units, using formaldehyde. 205

Helicobacter pylori seeks gastric mucosa, whether found in the stomach, duodenum, or Barrett's esophagus. Definitive diagnosis can be secured by appropriate stains of mucosal biopsies and culture, but the rapid urease test, breath isotope studies, and serologic testing are also useful. The frequency of colonization increases with advancing age, but infection occurs earlier in underdeveloped countries. Although the reservoir is uncertain, water or food transmission seems likely. There is sufficient evidence to assign an etiologic role to the bacteria in the causation of type B antral gastritis. H. pylori is found in areas of gastric metaplasia within the duodenum and is associated with duodenitis. Although acute infection leads to hypochlorhydria, chronic colonization has little effect on acid secretion. Studies have thus far failed to establish a convincing relationship between H. pylori and nonulcer dyspepsia, although the bacteria may play a role in selected patients. H. pylori is found in association with most idiopathic gastric and duodenal ulcers, but it is unclear as to whether the bacteria plays a causative or permissive role. The organism has a predilection for intercellular spaces and the mucous layer, thus affording relative isolation from luminally active antibiotics. Monotherapy with bismuth preparations transiently eliminates the bacteria, but recolonization is rapid, probably due to regrowth of sequestered organisms. A combination of metronidazole, bismuth, and tetracycline (or amoxicillin) affords the best eradication rate, but the potential side effects of this program should be considered. The present therapy of duodenal ulcer disease is effective and without significant risk. Treatment of H. pylori should be reserved for those patients who relapse on adequate maintenance therapy. If a safe and effective antibiotic becomes available, more frequent testing and earlier treatment intervention may become more attractive. H. pylori is probably an "innocent bystander" for most patients, but the bacteria may sufficiently impair the defenses of the antral and duodenal mucosa to facilitate the development and relapse of ulcer disease in subsets of patients.
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PMID:Helicobacter pylori: aggressor or innocent bystander? 207 88

Four Helicobacter pylori strains were used to develop in vitro methods to assess adherence to HeLa cells. Using direct detection by microscopy, adhesion scores increased with the initial bacteria-to-cell ratio. The urease method assessed H. pylori bound to HeLa cells by their urease activity. The percentage of the original inoculum adhering to HeLa cells remained constant for initial ratios from 10(2) to 10(5) bacteria per cell. An ELISA using anti-H. pylori serum assessed whole bacteria or components bound to HeLa cell fractions. By all three methods, the four H. pylori strains were adherent to HeLa cells or membranes whereas Campylobacter fetus and Providencia control strains were not. The adherence of H. pylori whole cells decreased following extraction with saline, water, or glycine buffer and most of the superficial adhering material (SAM) was present in the saline or water extracts. SAM bound better to HeLa membranes than to calf fetuin or bovine serum albumin (BSA); binding was inhibited by preincubation of SAM with HeLa membranes but not with fetuin or BSA or by pretreatment of HeLa membranes with neuraminidase. These data indicate that SAM has a specific receptor on the HeLa cell membranes. By gel exclusion chromatography of bacterial extracts, the most adherent components were found in the fractions which also contained the highest urease activity; these fractions included urease subunit antigens. We conclude that adherence of H. pylori can be assessed by microtiter assays and involves bacterial surface material which co-purifies with urease and is different from the N-acetyl-neuraminyl-lactose binding hemagglutinin.
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PMID:Adherence of Helicobacter pylori cells and their surface components to HeLa cell membranes. 209 96

Urease was purified 112-fold to homogeneity from the microaerophilic human gastric bacterium, Helicobacter pylori. The urease isolation procedure included a water extraction step, size exclusion chromatography, and anion exchange chromatography. The purified enzyme exhibited a Km of 0.3 +/- 0.1 mM and a Vmax of 1,100 +/- 200 mumols of urea hydrolyzed/min/mg of protein at 22 degrees C in 31 mM Tris-HCl, pH 8.0. The isoelectric point was 5.99 +/- 0.03. Molecular mass estimated for the native enzyme was 380,000 +/- 30,000 daltons, whereas subunit values of 62,000 +/- 2,000 and 30,000 +/- 1,000 were determined. The partial amino-terminal sequence (17 residues) of the large subunit of H. pylori urease (Mr = 62,000) was 76% homologous with an internal sequence of the homohexameric jack bean urease subunit (Mr = 90,770; Takashima, K., Suga, T., and Mamiya, G. (1988) Eur. J. Biochem. 175, 151-165) and was 65% homologous with amino-terminal sequences of the large subunits of heteropolymeric ureases from Proteus mirabilis (Mr = 73,000) and from Klebsiella aerogenes (Mr = 72,000; Mobley, H. L. T., and Hausinger, R. P. (1989) Microbiol. Rev. 53, 85-108). The amino-terminal sequence (20 residues) of the small subunit of H. pylori urease (Mr = 30,000) was 65 and 60% homologous with the amino-terminal sequences of the subunit of jack bean urease and with the Mr = 11,000 subunit of P. mirabilis urease (Jones, B. D., and Mobley, H. L. T. (1989) J. Bacteriol. 171, 6414-6422), respectively. Thus, the urease of H. pylori shows similarities to ureases found in plants and other bacteria. When used as antigens in an enzyme-linked immunosorbent assay, neither purified urease nor an Mr = 54,000 protein that co-purified with urease by size exclusion chromatography was as effective as crude preparations of H. pylori proteins at distinguishing sera from persons known either to be infected with H. pylori or not.
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PMID:Purification and characterization of urease from Helicobacter pylori. 218 75

Helicobacter pylori (H. pylori), ex-Campylobacter pylori, is now considered to be the causative agent of active chronic gastritis in humans and may be diagnosed by histology, gram-stain, culture, urease test or noninvasively by 14C-urea breath test. The aim of this study was to determine the sensitivity, specificity, and reproducibility of the breath test as compared with the microbiological (culture) "gold standard". Forty-one subjects were studied. Gastroscopy was performed in all participants and 2 antral mucosa biopsy specimens were taken for urease test and microbiological (gram-stain and culture) studies. The breath test was performed within one week after the gastroscopy. After fasting overnight, a control breath sample was obtained and a standard meal was offered to delay gastric emptying. Then, the participants drank 5 microCi of 14C-urea in 20 ml of water and breath samples were collected at 10, 15, 30 and 60 min in a hyamine-ethanol solution with a p-H indicator. A repeat test was performed in 9 subjects to assess test reproducibility. Twenty-nine subjects (71 percent) were Hp positive and 12 (29 percent) H. pylori negative. A highly significant difference (p less than 0.0001) was observed in 14CO2 exhalation in colonized and non-colonized subjects in samples collected at all times studied. As compared with culture we found that the breath test was 97 percent sensitive and 100 percent specific. We conclude that 14C-urea breath test is a simple, inexpensive, sensitive, and reliable method to detect H. pylori colonization. It is a useful test to epidemiologic and therapeutic trials.
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PMID:[14C-urea breath test to diagnose gastric Helicobacter pylori colonization]. 227 58

A halophilic gram-negative rod was isolated from blood and cerebrospinal fluid collected from a 70-year-old male having no known contact with seafood or salt water. Positive biochemical tests included oxidase, sensitivity to 0/129, O-nitrophenyl-beta-D-galactopyranoside, lysine decarboxylase and fermentation of glucose, salicin, n-inositol, sucrose, L-mannose, L-arabinose, and arbutin. Negative tests included indole, ornithine decarboxylase, arginine dihydrolase fermentation of lactose, and production of gelatinase and urease. The DNA base composition was 45.0 mol% guanine plus cytosine. Numerical taxonomy indicated 70% similarity with known reference Vibrio sp. strains. The 5S rRNA sequence for this strain has been determined: 5'-U G C C U G G C G A C C A U A G C G U U U U G G A C C C A C C U G A U U C C A U G C C G A A C U C A G U A G U G A A A C G A A A C A G C G U C G A U G G U A G U G U G G G G U C U C C C C A U G U G A G A G U A G A A C A U C G C C A G G C A U-3'. Based on the phenetic, molecular genetic, and nucleic acid sequencing data, it is concluded that Vibrio cincinnatiensis represents a new species of the genus Vibrio sensu strictu (as defined by 5S rRNA sequencing results). On a basis of 5S rRNA comparative sequence analysis, the organism appears to share a recent common ancestor with V. gazogenes (98% homology) and close ancestry with V. mimicus, V. fluvialis, and V. metschnikovii.
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PMID:Vibrio cincinnatiensis sp. nov., a new human pathogen. 242 96

A comparison was made of 27 'endemic' strains of Staphylococcus aureus and 35 strains from freshly slaughtered birds, isolated at five commercial slaughterhouses processing chickens or turkeys. Of 112 biochemical and physiological tests used, 74 gave results which differed among the strains. Cluster analysis revealed several distinct groupings which were influenced by strain type, processing plant and bird origin; these included a single group at the 72% level of similarity containing most of the 'endemic' strains. In comparison with strains from freshly slaughtered birds, a higher proportion of 'endemic' strains produced fibrinolysin, alpha-glucosidase and urease and were beta-haemolytic on sheep-blood agar. The 'endemic' type also showed a greater tendency to coagulate human but not bovine plasma, and to produce mucoid growth and clumping. The last two properties, relevant to colonization of processing equipment, were less evident in heart infusion broth than in richer media or process water collected during defeathering of the birds.
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PMID:Differentiation of Staphylococcus aureus from freshly slaughtered poultry and strains 'endemic' to processing plants by biochemical and physiological tests. 270 70


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