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)

Struvite renal stones are caused by infection of the urine with bacteria that synthesize the enzyme urease. Ammonium is released by the breakdown of urea by urease, the urine becomes highly alkaline, and magnesium ammonium phosphate (struvite) and carbonate apatite crystallize. Incorporation of the infecting bacteria within the developing stone, results in a focus of infection that is resistant to conventional antimicrobial therapy, and which is manifested clinically by repeated urinary tract infection caused by persistent bacteriuria. Extracorporeal shock wave lithotripsy (ESWL) currently is accepted as the election treatment for most renal calculi. This trial examines the bacteriologic aspects pre and post-ESWL. Eighty adult patients, 47 females and 33 males, without clinical signs of urinary tract infections (UTI) were submitted to urine cultures pre and post-ESWL. The first 50 patients underwent during and post-ESWL, 150 blood cultures, which all proved to be negative, confirming very low risk of generalized sepsis. No patient presented fever, chills or rigors pre or postprocedures. With respect to urine cultures 43 patients (52.5%) had a pre-ESWL UTI, in comparison to 49 (60%) who had a UTI post-ESWL. The distribution of organisms pre and post-ESWL was as follows: Proteus mirabilis (22/22), Escherichia coli (11/11), Pseudomonas aeruginosa (4/5), Klebsiella pneumoniae (2/2), Enterobacter cloacae (0/1), Alcaligenes odorans (1/2) Enterococcus faecalis (1/3), Staphylococcus saprophyticus (1/2) and Candida albicans (1/1). In this study 6 patients presented bacteriuria post-ESWL probably due to bacteria from inside the calculi. According to these results, the risk of bacteremia seems to be very low. In 60% of staghorn renal stones we could demonstrate a bacterial infection.
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PMID:[Staghorn renal lithiasis treated with shock waves. Bacteriologic aspects]. 765 75

In vivo activation of Klebsiella aerogenes urease, a nickel-containing enzyme, requires the presence of functional UreD, UreF, and UreG accessory proteins and is further facilitated by UreE. These accessory proteins are proposed to be involved in metallocenter assembly (M. H. Lee, S. B. Mulrooney, M. J. Renner, Y. Markowicz, and R. P. Hausinger, J. Bacteriol. 174:4324-4330, 1992). A series of three UreD-urease apoprotein complexes are present in cells that express ureD at high levels, and these complexes are thought to be essential for in vivo activation of the enzyme (I.-S. Park, M. B. Carr, and R. P. Hausinger, Proc. Natl. Acad. Sci. USA 91:3233-3237, 1994). In this study, we describe the effect of accessory gene deletions on urease complex formation. The ureE, ureF, and ureG gene products were found not to be required for formation of the UreD-urease complexes; however, the complexes from the ureF deletion mutant exhibited delayed elution during size exclusion chromatography. Because these last complexes were of typical UreD-urease sizes according to native gel electrophoretic analysis, we propose that UreF alters the conformation of the UreD-urease complexes. The same studies revealed the presence of an additional series of urease apoprotein complexes present only in cells containing ureD, ureF, and ureG, along with the urease subunit genes. These new complexes were shown to contain urease, UreD, UreF, and UreG. We propose that the UreD-UreF-UreG-urease apoprotein complexes represent the activation-competent form of urease apoprotein in the cell.
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PMID:Evidence for the presence of urease apoprotein complexes containing UreD, UreF, and UreG in cells that are competent for in vivo enzyme activation. 772 85

The crystal structure of urease from Klebsiella aerogenes has been determined at 2.2 A resolution and refined to an R factor of 18.2 percent. The enzyme contains four structural domains: three with novel folds playing structural roles, and an (alpha beta)8 barrel domain, which contains the bi-nickel center. The two active site nickels are 3.5 A apart. One nickel ion is coordinated by three ligands (with low occupancy of a fourth ligand) and the second is coordinated by five ligands. A carbamylated lysine provides an oxygen ligand to each nickel, explaining why carbon dioxide is required for the activation of urease apoenzyme. The structure is compatible with a catalytic mechanism whereby urea ligates Ni-1 to complete its tetrahedral coordination and a hydroxide ligand of Ni-2 attacks the carbonyl carbon. A surprisingly high structural similarity between the urease catalytic domain and that of the zinc-dependent adenosine deaminase reveals a remarkable example of active site divergence.
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PMID:The crystal structure of urease from Klebsiella aerogenes. 775 94

An open reading frame (ORF1) located upstream of the urease structural gene ureA in Rhizobium meliloti strain AK631 was cloned and characterized by DNA sequencing. Comparison of the amino acid sequence revealed partial homology with the urease accessory gene ureD of Klebsiella aerogenes and Proteus mirabilis. Mutational analysis of ORF1 showed that the gene is necessary for urease activity. Its function is still unknown.
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PMID:The urease structural gene ureA in Rhizobium meliloti is preceded by an open reading frame necessary for urease activity. 781 87

Preliminary results suggested that the diffusion in France of the SHV-4 extended-spectrum beta-lactamase was probably due to the spread of one single epidemic strain of Klebsiella pneumoniae. In this study, we tested various phenotypic and genotypic markers to compare K. pneumoniae strains producing this enzyme isolated in 14 French hospitals between 1987 and 1989. All of the strains were of the same capsule serotype, K25. Twelve of them were of the same biotype: weak urease activity and no sucrose fermentation. Among the six plasmid profiles observed, one accounted for eight strains. Large plasmids of 170 kb encoding SHV-4 beta-lactamase were present in all strains of K. pneumoniae and could be transferred by conjugation with high frequency to Escherichia coli J53-2 or HB101 from all except one strain. Plasmid EcoRI restriction patterns suggested that these plasmids were closely related and similar to pUD18 encoding SHV-3 beta-lactamase, originally described in France and differing from SHV-4 by one amino acid substitution. Ribotyping with EcoRI and HindIII and genomic fingerprinting with XbaI by pulsed-field gel electrophoresis were concordant and suggested that 12 of the isolates recovered from the 14 hospitals were probably the same strain. Dissemination in France of the SHV-4 extended-spectrum beta-lactamase was thus essentially due to the diffusion of a single K. pneumoniae clone.
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PMID:Molecular epidemiology of Klebsiella pneumoniae strains that produce SHV-4 beta-lactamase and which were isolated in 14 French hospitals. 781 97

Assembly of protein metallocenters is not well understood. Urease offers a tractable system for examination of this process. Formation of the urease metallocenter in vivo is known to require four accessory proteins: UreD, postulated to be a urease-specific molecular chaperone; UreE, a nickel(II)-binding protein; and UreF and UreG, of unknown function. Activation of purified Klebsiella aerogenes urease apoprotein was accomplished in vitro by providing carbon dioxide (half-maximal activation at approximately 0.2 percent carbon dioxide) in addition to nickel ion. Activation coincided with carbon dioxide incorporation into urease in a pH-dependent reaction (pKa > or = 9, where Ka is the acid constant). The concentration of carbon dioxide also affected the amount of activation of UreD-urease apoprotein complexes. These results suggest that carbon dioxide binding to urease apoprotein generates a ligand that facilitates productive nickel binding.
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PMID:Requirement of carbon dioxide for in vitro assembly of the urease nickel metallocenter. 785 93

HoxN, an integral membrane protein with seven transmembrane helices and a molecular mass of 33.1 kDa, is involved in high-affinity nickel transport in Alcaligenes eutrophus H16. From genetic analyses, it has been concluded that HoxN is a single-component ion carrier. To investigate this assumption, hoxN was introduced into Escherichia coli. The recombinant strain showed significantly enhanced nickel uptake in a short-interval assay. Likewise, growth in the presence of 63NiCl2 yielded a more than 15-fold-increased cellular nickel content. The HoxN-based nickel transport activity could also be demonstrated in a physiological assay: an E. coli strain coexpressing hoxN and the urease operon of Klebsiella aerogenes exhibited urease activity 10-fold greater than that in the strain lacking a functional hoxN. These results strongly suggest that HoxN is sufficient to operate as a nickel permease. Multiple sequence alignment of HoxN and four other bacterial membrane proteins implicated in nickel metabolism revealed two conserved signatures which may play a role in the nickel translocation process.
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PMID:The Alcaligenes eutrophus protein HoxN mediates nickel transport in Escherichia coli. 789 9

The formation of active urease in Klebsiella aerogenes requires the presence of three structural genes for the apoprotein (ureA, ureB, and ureC), as well as four accessory genes (ureD, ureE, ureF, and ureG) that are involved in functional assembly of the metallocenter in this nickel-containing enzyme. Slow and partial activation of urease apoprotein was observed after addition of nickel ion to extracts of Escherichia coli cells bearing a plasmid containing the K. aerogenes urease gene cluster or derivatives of this plasmid with deletions in ureE, ureF, or ureG. In contrast, extracts of cells containing a ureD deletion derivative failed to generate active urease, thus highlighting a key role for UreD in the metallocenter assembly process. Site-directed mutagenesis methods were used to overexpress ureD in the presence of the other urease genes, and the UreD protein was found to copurify with urease. A molecule of native urease apoprotein is capable of binding 0, 1, 2, or 3 molecules of UreD, consistent with a trimeric structure of urease catalytic units. The UreD-urease apoprotein complexes are competent for activation by nickel, with the level of activity obtained being directly related to the number of UreD molecules bound per urease molecule. Activation of the UreD-urease complexes is rapid and accompanied by UreD dissociation. We propose that UreD is a chaperone protein which stabilizes a urease apoprotein conformation that is competent for nickel incorporation.
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PMID:In vitro activation of urease apoprotein and role of UreD as a chaperone required for nickel metallocenter assembly. 790 61

The pre-formed urease activity of three NCTC reference strains and five clinical isolates of Helicobacter pylori was determined at room temperature (21 degrees C) and 37 degrees C by a viable cell count technique with a conventional urea slope test (Christensen's agar) as well as the commercial CLO-test. The urease activity of two gastroduodenal commensals, Proteus mirabilis and Klebsiella pneumoniae, was also tested. H. pylori strains produced positive reactions with viable cell counts of 10(6)-10(8) cfu within 30 min and with counts of 10(3)-10(6) cfu within 2 h. For some strains, smaller numbers of organisms were needed with the CLO-test than with the conventional test, and incubation of the CLO-test strips at 37 degrees C slightly decreased the number of organisms required for positive results. P. mirabilis produced a positive result on urea slopes with an initial inoculum of 10(7)-10(8) cfu at 2 h, but no positive reaction occurred for K. pneumoniae at 12 h, even with an initial inoculum of 10(11) cfu. However, both P. mirabilis and K. pneumoniae gave a positive result after incubation for 24 h with initial inocula of < 10(1) cfu and 10(3)-10(4) cfu respectively. Incubation at 37 degrees C significantly reduced the inoculum size of these organisms required for a positive result after incubation for 4 h when tested with the slopes, but not with the CLO-test. These findings indicate that H. pylori possesses much greater pre-formed urease activity than P. mirabilis and K. pneumoniae. False negative results for clinical detection of H. pylori in gastroduodenal biopsies may be due to small numbers of organisms, especially after treatment with antimicrobial agents, and false positive results may arise from gastroduodenal commensals or contaminants.
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PMID:Pre-formed urease activity of Helicobacter pylori as determined by a viable cell count technique--clinical implications. 800 37

A 4.6 kb DNA region of the Rhizobium meliloti strain AK631 was found to contain seven open reading frames (ORFs), all oriented in the same direction. The putative gene products of four of these ORFs were highly homologous to UreA, UreB and UreC of Klebsiella aerogenes, Proteus mirabilis, Proteus vulgaris and Canavalia ensiformis. The overall organisation of the DNA region analysed was ORF1, ureA (ORF2), ORF3, ureB (ORF4), ORF5, ORF6 and ureC (ORF7), indicating that the organisation of the urease structural genes in R. meliloti differs from that of other urease genes so far characterized. ORF1 was incomplete; only the 3' end of the coding region was present. The six complete ORFs coded for polypeptides of 11.1 (UreA), 8.9 (ORF3), 10.8 (UreB), 15.0 (ORF5), 13.8 (ORF6) and 60.7 kDa (UreC). No sequence homology to known polypeptides could be detected for the gene products of ORF1, ORF3, ORF5 and ORF6. Using a lacZ fusion and insertional mutagenesis it was shown that the seven ORFs identified were all located in the same transcription unit. For mutational analysis a resistance gene cassette was introduced into each of the complete ORFs resulting in apolar mutations. Mutations in ureA, ureB and ureC, but not in ORF3, ORF5 and ORF6, abolished urease activity in R. meliloti. The determination of hydrogen uptake in these R. meliloti mutants revealed that only ORF6 and ureB are necessary for hydrogen uptake.
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PMID:A 4.6 kb DNA region of Rhizobium meliloti involved in determining urease and hydrogenase activities carries the structural genes for urease (ureA, ureB, ureC) interrupted by other open reading frames. 812 12


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