Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:6.3.4.6 (urease)
 7,490 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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.
 ...
PMID:Adherence of Helicobacter pylori cells and their surface components to HeLa cell membranes. 209 96

The specific activity of urease, nitrogenase, hialuronidase and neuraminidase in Y. pseudotuberculosis grown in different culture media and at different temperature has been studied. These enzymes have been found capable of functioning at both relatively low (2-8 degrees C) and high (37 degrees C) temperatures. The thermoadaptive properties of Y. pseudotuberculosis within a wide range of temperatures are ensured by the constant presence of isoenzymes, functioning only at low temperatures or only at high temperatures, in the microbial cells. Low temperature in combination with a definite culture medium triggers the activity of certain enzymatic systems, which explains, to some extent, the biochemical mechanisms of the psychrophilic properties of Y. pseudotuberculosis.
 ...
PMID:[Fermentative mechanisms of the psychrophilicity of Yersinia tuberculosis]. 636 42

Adherence of Ureaplasma urealyticum cells to eukaryotic cell monolayers was quantified using the Bertholet assay to monitor ammonia produced from urea by ureaplasma urease. Adherence was abolished by pre-treatment of ureaplasmas with HeLa cell extracts and inhibited to varying degrees by pretreatment of the ureaplasmas with N-acetylneuraminic acid, specific antisera and monoclonal antibodies. The data suggest the presence of several ureaplasma adhesins, some of which are species- or serotype-specific and some of which are proteinaceous and antigenic. The serotype-8-specific 96 kDa surface-expressed antigen may be one adhesin. Pre-treatment of HeLa cell monolayers with neuraminidase significantly reduced ureaplasma adherence and, using a novel 'immunoblot adherence assay', ureaplasmas were shown to bind to a number of HeLa cell components, three of which appear to terminate in sialic acid.
 ...
PMID:Adherence of Ureaplasma urealyticum to human epithelial cells. 800 May 51

Helicobacterpylori, the ulcer pathogen residing in the human stomach, binds to epithelial cells of the gastric antrum. We have examined binding of 13 bacterial isolates to epithelial cell lines by use of a sensitive microtiter plate method in which measurement of bacterial urease activity provides the means for quantitation of bound organisms. Several established human gastrointestinal carcinoma cell lines grown as monolayers were compared for suitability in these assays, and the duodenum-derived cell line HuTu-80 was selected for testing bacterial binding inhibitors. When bacteria are pretreated with oligosaccharides, glycoproteins, and glycolipids, a complex picture of bacterial-epithelial adherence specificities emerges. Among the monovalent inhibitors tested, 3'-sialyllactose (NeuAc alpha2-3Gal beta1-4Glc; 3'SL) was the most active oligosaccharide, inhibiting adherence for recent clinical isolates of H. pylori with a millimolar 50% inhibitory concentration (IC50). Its alpha2-6 isomer (6'SL) was less active. Most of the recent clinical isolates examined were inhibited by sialyllactose, whereas long-passaged isolates were insensitive. Among the long-passaged bacterial strains whose binding was not inhibited by 3'SL was the strain ATCC 43504, also known as NCTC 11637 and CCUG 17874, in which the proposed sialyllactose adhesin was recently reported to lack surface expression (P. G. O'Toole, L. Janzon, P. Doig, J. Huang, M. Kostrzynska, and T. H. Trust, J. Bacteriol. 177:6049-6057, 1995). Pretreatment of the epithelial monolayer with neuraminidase reduced the extent of binding by those bacteria that are sensitive to inhibition by 3'SL. Other potent inhibitors of bacterial binding are the glycoproteins alpha1-acid glycoprotein, fetuin, porcine gastric and bovine submaxillary mucins, and the glycolipid sulfatide, all of which present multivalent sialylated and/or sulfated galactosyl residues under the conditions of the binding assay. Consistent with this pattern, a multivalent neoglycoconjugate containing 20 mol of 3'SL per mol of human serum albumin inhibited bacterial binding with micromolar IC50. The H. pylori isolate most sensitive to inhibition by 3'SL was least sensitive to inhibition by sulfatide, gastric mucin, and other sulfated oligosaccharides. Bacteria that have been allowed to bind epithelial cells are also effectively detached by 3'SL. These results describe a heterogeneous adherence repertoire for these bacteria, but they also confirm the critical role of the 3'SL structure on human gastric epithelial cells as an adherence ligand for recent isolates of H. pylori.
 ...
PMID:Inhibition of Helicobacter pylori binding to gastrointestinal epithelial cells by sialic acid-containing oligosaccharides. 900 38

Helicobacter pylori colonises the stomach of man and induces a strong mucosal inflammation and a local and systemic immune response. Differences in virulence characteristics of Helicobacter pylori isolates can account for different clinical outcomes of infection. Most determinants of Helicobacter pylori pathogenicity factors are present in all isolates examined; some are present only in or expressed more intensively by certain strains. Many enzymes, i.e., urease, mucinase, phospholipases, alcohol dehydrogenase, neuraminidase, etc. could promote tissue erosion and ulceration by destroying the integrity of mucous, by inducing lipid peroxidation, etc. Strains which express the vacuolating toxin VacA and the associated protein CagA are called Type I and are considered endowed with increased ulcerogenic and inflammatory potential. Type I Helicobacter pylori strains carry a 40 kb genomic fragment called cag which is absent in Type II strains (VacA and CagA negative), and which contains numerous genes encoding for protein homologues to virulence factors expressed by other bacterial pathogens. CagA positive strains are more likely to be isolated from patients with duodenal ulcer and other severe digestive diseases. A simple serological test can help to detect patients at increased risk of developing severe gastroduodenal diseases, which can, therefore, possibly be prevented.
 ...
PMID:Are Helicobacter pylori differences important in the development of Helicobacter pylori-related diseases? 947 94

Many putative virulence determinants of Helicobacter pylori are believed to trigger and worsen the gastroduodenal mucosa damage observed in infected patients. H. pylori urease reacts with the gastric urea and generates ammonia; ammonia combines with water and yields ammonium hydroxide, which is cytotoxic. Ammonia may also inhibit cell proliferation and cause indirect mucosal injury by stimulating neutrophils. Phospholipases may damage the gastric mucosa by degrading phospholipids and generating precursors of ulcerogenic components. Other enzymes, such as protease, neuraminidase, fucosidase, and alcohol dehydrogenase, can contribute to damage of the gastric epithelium by destroying the integrity of mucus or by inducing lipid peroxidation. Infection by vacuolating cytotoxic (VacA+) H. pylori strains is considered to constitute increased risk for development of peptic ulcer and gastric cancer. Exploration of the vacA gene structure has shown the existence of strongly toxigenic strains, and has confirmed at the molecular level the increased ulcerogenic potential of VacA+ H. pylori strains. A pathogenicity island called cag has been recently described in Type 1 H. pylori strains (VacA+/CagA+).cag contains the cagA gene (whose expression is associated with toxigenicity) and many genes, some of which are highly homologous to virulence genes of other virulent bacteria, that account for the enhanced pathogenic potential of CagA+ organisms.
 ...
PMID:Helicobacter pylori factors involved in the development of gastroduodenal mucosal damage and ulceration. 947 42