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)

Urease activity has recently been shown to be an important virulence determinant for Helicobacter pylori, allowing it to survive the low pH of the stomach during colonization. Experimental murine infection with Helicobacter felis is now being used as a model for H. pylori infection to study the effects of vaccines, antibiotics, and urease inhibitors on colonization. However, little information comparing the ureases of H. felis and H. pylori is available. Urease was partially purified from the cell surface of H. felis ATCC 49179 by A-5M agarose chromatography, resulting in an eightfold increase in specific activity over that of crude urease. The apparent Km for urea for the partially purified urease was 0.4 mM, and the enzyme was inhibited in a competitive manner by flurofamide (50% inhibitory concentration = 0.12 microM). Antiserum to whole cells of H. pylori recognized both H. pylori and H. felis urease B subunits. Antiserum raised against H. felis whole cells recognized the large and small autologous urease subunits and the cpn60 heat shock molecule in both H. felis and H. pylori. However, this antiserum showed only a weak reaction with the B subunit of H. pylori urease. Two oligomeric DNA sequences were used as probes to evaluate the relatedness of H. felis and H. pylori urease gene sequences. One 30-mer from the ureA sequence, which had been shown previously to be specific for H. pylori, failed to hybridize to H. felis genomic DNA. A probe to the putative coding sequence for the active site of the H. pylori ureB subunit hybridized at low intensity to a 2.8-kb fragment of BamHI-HindIII-digested H. felis DNA, suggesting that the sequences were homologous but not identical, a result confirmed from the recently published sequences of ureA and ureB from H. felis.
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PMID:Immunological and molecular characterization of Helicobacter felis urease. 811 50

Urease is an important virulence factor for Helicobacter pylori and is critical for bacterial colonization of the human gastric mucosa. Specific inhibition of urease activity has been proposed as a possible strategy to fight this bacteria which infects billions of individual throughout the world and can lead to severe pathological conditions in a limited number of cases. We have selected peptides which specifically bind and inhibit H. pylori urease from libraries of random peptides displayed on filamentous phage in the context of pIII coat protein. Screening of a highly diverse 25-mer combinatorial library and two newly constructed random 6-mer peptide libraries on solid phase H. pylori urease holoenzyme allowed the identification of two peptides, 24-mer TFLPQPRCSALLRYLSEDGVIVPS and 6-mer YDFYWW that can bind and inhibit the activity of urease purified from H. pylori. These two peptides were chemically synthesized and their inhibition constants (Ki) were found to be 47 microM for the 24-mer and 30 microM for the 6-mer peptide. Both peptides specifically inhibited the activity of H. pylori urease but not that of Bacillus pasteurii.
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PMID:New inhibitors of Helicobacter pylori urease holoenzyme selected from phage-displayed peptide libraries. 1041 39

It has been shown previously [Brown, C.M. & Tate, W.P. (1994) J. Biol. Chem. 269, 33164-33170.] that the polypeptide chain release factor RF2 involved in translation termination in prokaryotes was able to photocrossreact with mini-messenger RNAs containing stop signals in which U was replaced by 4-thiouridine (s4U). Here, using the same strategy we have monitored photocrosslinking to eukaryotic ribosomal components of 14-mer mRNA in the presence of tRNA(f)(Met), and 42-mer mRNA in the presence of tRNA(Asp) (tRNA(Asp) gene transcript). We show that: (a) both 14-mer and 42-mer mRNAs crossreact with ribosomal RNA and ribosomal proteins. The patterns of the crosslinked ribosomal proteins are similar with both mRNAs and sensitive to ionic conditions; (b) the crosslinking patterns obtained with 42-mer mRNAs show characteristic modification upon addition of tRNA(Asp) providing evidence for appropriate mRNA phasing onto the ribosome. Similar changes are not detected with the 14-mer mRNA.tRNA(f)(Met) pairs; (c) when eukaryotic polypeptide chain release factor 1 (eRF1) is added to the ribosome.tRNA(Asp) complex it crossreacts with the 42-mer mRNA containing the s(4)UGA stop codon located in the A site, but not with the s(4)UCA sense codon; this crosslink involves the N-terminal and middle domains of eRF1 but not the C domain which interacts with eukaryotic polypeptide chain release factor 3 (eRF3); (d) addition of eRF3 has no effect on the yield of eRF1-42-mer mRNA crosslinking and eRF3 does not crossreact with 42-mer mRNA. These experiments delineate the in vitro conditions allowing optimal phasing of mRNA on the eukaryotic ribosome and demonstrate a direct and specific contact of 'core' eRF1 and s(4)UGA stop codon within the ribosomal A site.
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PMID:The polypeptide chain release factor eRF1 specifically contacts the s(4)UGA stop codon located in the A site of eukaryotic ribosomes. 1135 6

We previously reported a mouse monoclonal antibody (MAb), termed L2, specific for Helicobacter pylori urease strongly inhibited its enzymatic activity. Here, to gain insight into how this antibody affects urease activity, the epitope that was recognized by the antibody was determined. By screening a panel of overlapping synthetic peptides covering the entire sequence of the two subunits (UreA and UreB), we identified a stretch of UreB-derived 19 amino acid (aa) residues (UB-33; aa 321 to 339, CHHLDKSIKEDVQFADSRI) that was specifically recognized by the L2 antibody. Further sequential amino acid deletion of the 19-mer peptide from either end allowed us to determine the minimal epitope as 8 amino acid residues (F8; SIKEDVQF) for L2 reactivity. This epitope appears to lie exactly on a short sequence which formed a flap over the active site of urease, suggesting that binding of the L2 antibody sterically inhibits access of urea, the substrate of urease. Finally, immunization of rabbits with either the 19-mer peptide or the 8-mer minimal epitope resulted in generation of antiurease antibodies that were capable of inhibiting the enzymatic activity. Since urease is critical for virulence of H. pylori, antigenic peptides that induce production of antibodies to inhibit its enzymatic activity may potentially be a useful tool as a vaccine for prevention and treatment of H. pylori infection.
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PMID:Identification of an antigenic epitope in Helicobacter pylori urease that induces neutralizing antibody production. 1159 27

Two characteristic monoclonal antibodies (HpU-2 and -18) out of 26 monoclonal antibodies (HpU-1 approximately 26) produced against Helicobacter pylori (H. pylori) urease showed a strong inhibitory effect against the enzymatic activity of the urease. Epitope mapping about some monoclonal antibodies of the HpU-series inhibiting enzymatic activity was performed by using a surface plasmon resonance apparatus and by digesting H. pylori urease with trypsin, followed by mass spectroscopy. The sequences of the epitopes recognized by HpU-2 and -18 were SVELIDIGGNRRIFGFNALVDR (22 mer) and IFGFNALVDR (10 mer), respectively. The former sequence is present as a part of a loop structure at a position close to the C-terminal of the alpha-subunit of H. pylori urease, although it has been suggested that the active site of the urease resides in the beta-subunit. The above peptide (22 mer) was chemically synthesized in a linear and cyclic form, and its conjugate with BSA was immunized in rabbits. The resultant serum induced by the linear form could specifically bind to H. pylori infecting human gastric mucosa. These results suggest that the above sequence (22 mer) must be an important epitope, although it locates in the alpha-subunit but not in the beta-subunit.
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PMID:Epitope mapping and features of the epitope for monoclonal antibodies inhibiting enzymatic activity of Helicobacter pylori urease. 1511 96

Gastric colonization of Helicobacter pylori (H. pylori) occurs in a very early age via infected mothers having H. pylori-specific IgG antibodies that would be transplacentally transferred to infants. In addition, H. pylori urease-specific IgG was associated with chronic gastric atrophy and post-immunization gastritis is usually correlated with a strong local IgG response. These findings indicate that H. pylori-specific IgG antibodies, in particular its urease-specific IgG, may induce unfavorable influence on host resistance against H. pylori. Here, we show that we have found a unique H. pylori urease-specific IgG monoclonal antibody (MAb), termed S3, recognizing the conformational structure of the small subunit Ure-A, which enhanced the urease enzymatic activity. Such enhancement of the H. pylori urease activity induced by 1 microg of S3 was almost completely cancelled by simultaneously added the same amount of L2 MAb, which has a strong and specific inhibitory activity against H. pylori urease and recognizes a liner epitope of 8-mer peptide (F8: SIKEDVQF) within its large subunit Ure-B (Infect. Immun. 69: 6597, 2001). Intravenous pre-administration of purified S3 into BALB/c mice showed significant augmentation for gastric colonization with the susceptible strain Sydney Strain-1 (SS-1). To our knowledge, this is the first demonstration that a H. pylori urease-specific IgG MAb induced an augmentation of their gastric colonization in vivo.
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PMID:Augmentation of Helicobacter pylori urease activity by its specific IgG antibody: implications for bacterial colonization enhancement. 1580 82

Helicobacter pylori (H. pylori) urease is a key protein for persistent infection of the bacteria in the stomach. Although H. pylori generally induce anti-H. pylori-specific antibodies (Abs), these Abs do not usually work for eradication or prevention of the H. pylori infection. In our previous study, we identified a linear epitope composed of 19-mer peptides termed UB-33, CHHLDKSIKEDVQFADSRI, within the large subunit of H. pylori urease. Anti-UB-33-specific Abs neutralized the enzymatic activity of H. pylori urease in vitro. In the present study, we evaluated the effect of immunization of BALB/c mice with H. pylori UB-33 peptide. After confirming the production of anti-UB-33-specific Abs, mice were challenged orally with H. pylori Sydney Strain-1 (SS-1). Mice producing anti-UB-33-specific Abs were not infected with SS-1, and the amount of SS-1 isolate in their stomach was significantly reduced. Also, the urease-negative mutant of H. pylori, HPP1801, did not colonize in the stomach, indicating that H. pylori urease was a critical element for infection of H. pylori in the gastric mucosa. Moreover, mice producing UB-33-specific Abs apparently suppressed H. pylori infection in the stomach where anti-UB-33 Abs were secreted in the gastric juice, indicating that H. pylori colonization was inhibited in the presence of anti-UB-33 Abs. In addition, the neutralization activity of sera from mice immunized with purified urease was less potent than that in the sera from mice immunized with UB-33. Furthermore, the recognition of epitope UB-33 was mediated through Toll-like receptor 2 (TLR2) on the B-1 cells using TLR2-knockout BALB/c mice in vivo. These results indicate that liner peptide UB-33 should be used for immunization to induce neutralizing Abs instead of purified H. pylori urease to prevent H. pylori infection and their colonization in the stomach.
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PMID:Neutralizing antibodies for Helicobacter pylori urease inhibit bacterial colonization in the murine stomach in vivo. 3098 4