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)

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.
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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.
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PMID:Helicobacter pylori factors involved in the development of gastroduodenal mucosal damage and ulceration. 947 42

We report the results of x-ray reflectivity measurements of thin films formed by different water-soluble proteins at the air-aqueous solution interface. It is demonstrated that glucose oxidase, alcohol dehydrogenase, and urease molecules denaturate at the air-aqueous solution interface to form 8- to 14-A-thick peptide sheets. X-ray reflectivity data indicate that the spreading of a lipid monolayer at the aqueous solution surface before protein injection does not prevent proteins from unfolding. On the other hand, crosslinking of proteins results in intact enzyme layers at the subphase surface. A model that involves interaction of glucose oxidase molecules with a phospholipid monolayer is proposed. In this model, an observed decrease of the lipid electron density in the protein presence is explained in terms of "holes" in the monolayer film caused by protein molecule adsorption.
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PMID:Protein folding at the air-water interface studied with x-ray reflectivity. 1007 57

Chaperonins suppress the denaturation of proteins and promote protein folding in vivo. Because hyperthermophilic chaperonins are expected to be used as a stabilizer for proteins, the effects of a group II chaperonin from a hyperthermophilic archaeum, Thermococcus strain KS-1 (T. KS-1 cpn), on the stabilization of mesophilic and thermophilic free enzymes and an enzyme co-immobilized with T. KS-1 cpn were studied. T. KS-1 cpn prevented the thermal inactivation of yeast alcohol dehydrogenase (ADH), jack bean urease, and Thermus flavus malate dehydrogenase (MDH) at high temperatures. T. KS-1 cpn also improved the long-term stability of ADH at lower temperatures. Moreover, the residual ADH activity of ADH co-entrapped with T. KS-1 cpn was improved and maintained at a higher level than that of the entrapped ADH without chaperonin. T. KS-1 cpn is useful for the stabilization of free and immobilized enzymes and applicable to various fields of biotechnology.
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PMID:Stabilization of free and immobilized enzymes using hyperthermophilic chaperonin. 1656 8

Urea could be effectively converted into L-glutamic acid with semipermeable nylon-polyethylenimine artificial cells containing L-glutamic dehydrogenase (EC 1.4.1. 3), yeast alcohol dehydrogenase (EC 1.1.1.1), urease (EC 3.5.1. 5) and soluble dextran-NAD(+). For batch conversion, the artificial cell suspension to total reaction volume ratios ranged from 1 in 5 to 1 in 60. From 22.6 to 53.4 micromol of L-glutamic acid could be produced by 0.4 mL artificial cell suspension within 2 h. The corresponding conversion ratios were 56.5-11. 1%. The L-glutamic dehydrogenase multienzyme system showed a good storage stability: 66.0% of the original activity was retained after 1 month of storage at 4 degrees C. A small bioreactor was prepared to contain 4.0 mL artificial cells. At a flow rate of SV = 1.5 h(-1), the maximum conversion rate was 49.6 micromol L-glutamic acid/p h. Thirty-eight percent of the maximum activity was retained when continuously used for four days at 22 degrees C. A kinetic analysis for the L-glutamic dehydrogenase multienzyme system was studied. The Michaelis constants are as follows: alpha-ketoglutarate is 0.838 mM; urea is 1.90 mM; dextran- NAD(+) is 0.345 mM; and ethanol is 5.31 mM.
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PMID:Conversion of alpha-ketoglutarate into L-glutamic acid with urea as ammonium source using multienzyme systems and dextran-NAD+ immobilized by microencapsulation within artificial cells in a bioreactor. 1858 59

We prepared artificial cells each containing leucine dehydrogenase (EC 1.4.1.9), urease (EC 3.5.1.5), soluble dextran-NAD(+), and one of the following coenzyme regenerating dehydrogenases: glucose dehydrogenase (EC 1.1.1.47); yeast alcohol dehydrogenase (EC 1.1.1.1); malate dehydrogenase (EC 1.1.1.37); or lactate dehydrogenase (EC 1.1.1.27). Artificial cells were packed in small columns. L-Leucine, L-valine, and L-isoleucine were continuously produced with simultaneous dextran-NADH regeneration. The maximum production ratios depended on the coenzyme regenerating systems used: 83-93% for D-glucose and glucose dehydrogenase system; 90% for ethanol and yeast alcohol dehydrogenase system; 45-55% for L-malate and malate dehydrogenase system; and 64-78% for L-lactate and lactate dehydrogenase system. Kinetic experiments were also carried out. The apparent K(m) values are as follows: 0.33 mM for alpha-ketoisocaproate (KIC); 0.51 mM for alpha-ketoisovalerate (KIV); 0.58 mM for DL-alpha-keto-beta-methyl-n-valerate (KMV); 3.52 mM for urea; 27.82 mM for D-glucose; 3.89 mM for ethanol; 3.02 mM for L-malate; and 16.67 mM for L-lactate. Kinetic analysis showed that KIC, KIV, and KMV were all competitive inhibitors in the reactions catalyzed by leucine dehydrogenase. Their inhibitor constants were the corresponding K(m) values.
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PMID:Production of essential L-branched-chain amino acids in bioreactors containing artificial cells immobilized multienzyme systems and dextran-NAD+. 1859 77

A "smart" biofuel cell switchable ON and OFF upon application of several chemical signals processed by an enzyme logic network was designed. The biocomputing system performing logic operations on the input signals was composed of four enzymes: alcohol dehydrogenase (ADH), amyloglucosidase (AGS), invertase (INV) and glucose dehydrogenase (GDH). These enzymes were activated by different combinations of chemical input signals: NADH, acetaldehyde, maltose and sucrose. The sequence of biochemical reactions catalyzed by the enzymes models a logic network composed of concatenated AND/OR gates. Upon application of specific "successful" patterns of the chemical input signals, the cascade of biochemical reactions resulted in the formation of gluconic acid, thus producing acidic pH in the solution. This resulted in the activation of a pH-sensitive redox-polymer-modified cathode in the biofuel cell, thus, switching ON the entire cell and dramatically increasing its power output. Application of another chemical signal (urea in the presence of urease) resulted in the return to the initial neutral pH value, when the O(2)-reducing cathode and the entire cell are in the mute state. The reversible activation-inactivation of the biofuel cell was controlled by the enzymatic reactions logically processing a number of chemical input signals applied in different combinations. The studied biofuel cell exemplifies a new kind of bioelectronic device where the bioelectronic function is controlled by a biocomputing system. Such devices will provide a new dimension in bioelectronics and biocomputing benefiting from the integration of both concepts.
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PMID:Biofuel cell controlled by enzyme logic network--approaching physiologically regulated devices. 1935 82

It was recently shown that, as in yeast, alcohols selectively increase the hemolytic properties of certain staphylococci strains. This phenomenon has been called 'microbial alcohol-conferred hemolysis'(MACH). Here we present the changes in gene expression by Staphylococcus aureus 8325-4, in response to ethanol. Ethanol upregulated the expression of multiple toxins and increase the pathogen potential of S. aureus strain 8325-4. Ethanol also increased the level of genes considered necessary for production and viability of biofilm, such as: icaAD, sdrDE, pyr, and ure. Increased urease activity appeared to be an important factor in the ethanol response along with macromolecule repair mechanisms. Oxidative-stress responses, such as increased expression of sodA1, sodA2 and upregulation of zinc-containing alcohol dehydrogenase, alcohol-acetaldehyde dehydrogenase (adhE) and two aldehyde dehydrogenases (aldA1, aldA2), which can generate more reducing power, were also induced. Upregulation of fatty acid metabolism appears to be important in enabling the bacteria to handle excess amounts of ethanol which ultimately may lead to synthesis of lytic lypids. The patterns of regulation were confirmed by quantitive reverse transcriptase PCR (QRT-PCR). These results, taken together, suggest that exposure to ethanol increases pathogenic traits and induce oxidative-stress responses.
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PMID:Global gene expression in Staphylococcus aureus following exposure to alcohol. 1990 May 30


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