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)

To evaluate partial or total replacement of renal function using gut, we measured in vivo transport of nitrogen metabolites, electrolytes, and water into a jejunal segment configured as a continent reservoir in the dog. Reservoir contents were sampled and analyzed at serial time intervals during a 3-h period after instillation of solution containing (in mM) 40 NaCl, 10 NaHCO3, 220 mannitol, pH 8.5, without or with added urease. At 10 min postinstillation, the amount of urea in the solution without added urease was 3-5 times greater than in the presence of added urease, but accumulation of NH4+ was 14-21 times greater in the solution containing added urease, giving a luminal NH4+ concentration up to 10,000 times that of plasma. In the absence of urease, HCO3- concentration fell to 0, and pH declined to 6 at 3 h; in the presence of urease, HCO3- concentration was 4.5 mM, and pH was 7.8 at 3 h. We conclude 1) urea is secreted by the reservoir; 2) H+ is secreted and/or formed in the reservoir; 3) in the presence of urease, urea hydrolyzed to NH3 is converted to NH4+ by H+ and trapped in the lumen; and 4) in the urease solution, H+ binding by NH3 preserves luminal HCO3-, maintaining the initial pH. Thus the continent jejunal reservoir may supplement or replace impaired renal function.
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PMID:Transport properties of an in situ jejunal reservoir in dogs. 155 68

Proteus mirabilis, a common cause of urinary tract infection, can lead to serious complications including pyelonephritis. Adherence factors, urease, and hemolysin may be virulence determinants. These factors were compared for bacteria cultured from 16 patients with acute pyelonephritis and 35 with catheter-associated bacteriuria and for 20 fecal isolates. Pyelonephritis isolates were more likely (P less than .05) to express the mannose-resistant/Proteus-like (MR/P) hemagglutinin in the absence of mannose-resistant/Klebsiella-like (MR/K) hemagglutinin than were catheter-associated or fecal isolates. Pyelonephritis isolates produced urease activity of 63 +/- 27 (mean +/- SD) mumol of NH3/min/mg of protein, not significantly different from catheter-associated or fecal isolates. Hybridization of Southern blots of P. mirabilis chromosomal DNA with two urease gene probes demonstrated that urease gene sequences were conserved in all isolates. Geometric mean of reciprocal hemolytic titers for pyelonephritis isolates was 27.9; for urinary catheter isolates, 18.0; and for fecal isolates, 55.7 (not significantly different, P greater than .1). Although in vivo expression of urease and hemolysin may not be reliable indexes of virulence, MR/P hemagglutination in the absence of MR/K hemagglutination may be necessary for development of pyelonephritis.
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PMID:Hemagglutinin, urease, and hemolysin production by Proteus mirabilis from clinical sources. 217 24

The correlation between urease activity of Campylobacter pylori and atrophic gastritis was studied. On the basis of fundamental study on the optimal pH of C. pylori urease activity, urease activity of 38 biopsied specimens were measured under pH 5 condition, and compared with the positive ratio of C. pylori. In this study, sensitivity was 86.7%, and specificity was 87.0%, respectively. Mean urease activity of C. pylori positive specimens was 3.69 mIU/mg protein, and under this condition, C. pylori was likely to produce ammonia of 0.0218 mumole per minute, enough to damage the gastric mucosa. In addition, there was encountered high urease activity in the specimens which showed moderate glandular atrophy and severe mucosal inflammation. In conclusion, urea-urease-NH3 sequence is most likely to have some association with gastric glandular atrophy.
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PMID:[Correlation between Campylobacter pylori and chronic atrophic gastritis]. 225 Mar 90

The indirect interactions between the carbonic anhydrase (CA) and urease (UR) are investigated in the present work using rate determinations detected by combined potentiometric measurements. It is shown that, in accord with the mass-action law for the two enzyme catalyzed reactions, the two enzymes assume a synergic pattern: the increase in the rate of removal of CO2 from the solution facilitated by CA increases the rate of production of NH3 consequent from urea dissociation. The experimental system which has been set up to monitor these interactions consists of a potentiometric apparatus to follow the gaseous exchanges of CO2 and NH3 which take place from a buffered solution containing both CA and UR. The results of the present work are consistent with, and add a further support to the finding of Dodgson and Forster, who first demonstrated in vivo the existence of an indirect linkage between urea production and CA catalytic activity.
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PMID:Carbonic anhydrase and urease: an investigation in vitro on the possibility of a synergic action. 250 84

The diagnostic relevance of measurement of ammonia (NH3) in not stimulated gastric juice in patients with campylobacter pylori associated gastritis (CPAG) is in discussion. The role of CP-urease induced NH3 in pathogenesis of active gastritis is unclear. In answering to this questions we evaluated the sensitivity and specifity of NH3-test and CLO-test in cases of CPAG (n = 50), non CPAG (n = 16) and normal gastric mucosa (n = 20). We found a 88% sensitivity and a 86% specifity for NH3-test, a sensitivity for CLO-test of 80% and a specifity rate of 87%. NH3-test correlated well with CLO-test (n = 51, p less than 0.01) and semiquantitative histological identification of CP (p less than 0.01, n = 22). On the other hand we tried to correlate the amount of NH3 in the gastric juice and the histological degree of gastritis activity (infiltration of leucocytes of the lamia propria) in CPAG (n = 78) and Non-CPAG (n = 32) and before and after therapy in CPAG (n = 9) with bismuthsubnitrate (2 g/d, 14 d). There was no correlation between the amount of NH3 and the degree of active chronic gastritis in patients with CPAG (with or without therapy) and patients with non CPAG. It seems that NH3 has a diagnostic but no pathogenetic role in the process of inflammatory activity of CPAG.
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PMID:[Intragastric formation of ammonia in Campylobacter pylori associated gastritis. Diagnostic and pathogenetic significance]. 267 29

Proteus mirabilis, a common cause of urinary tract infection, produces a potent urease that hydrolyzes urea to NH3 and CO2, initiating kidney stone formation. Urease genes, which were localized to a 7.6-kilobase-pair region of DNA, were sequenced by using the dideoxy method. Six open reading frames were found within a region of 4,952 base pairs which were predicted to encode polypeptides of 31.0 (ureD), 11.0 (ureA), 12.2 (ureB), 61.0 (ureC), 17.9 (ureE), and 23.0 (ureF) kilodaltons (kDa). Each open reading frame was preceded by a ribosome-binding site, with the exception of ureE. Putative promoterlike sequences were identified upstream of ureD, ureA, and ureF. Possible termination sites were found downstream of ureD, ureC, and ureF. Structural subunits of the enzyme were encoded by ureA, ureB, and ureC and were translated from a single transcript in the order of 11.0, 12.2, and 61.0 kDa. When the deduced amino acid sequences of the P. mirabilis urease subunits were compared with the amino acid sequence of the jack bean urease, significant amino acid similarity was observed (58% exact matches; 73% exact plus conservative replacements). The 11.0-kDa polypeptide aligned with the N-terminal residues of the plant enzyme, the 12.2-kDa polypeptide lined up with internal residues, and the 61.0-kDa polypeptide matched with the C-terminal residues, suggesting an evolutionary relationship of the urease genes of jack bean and P. mirabilis.
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PMID:Proteus mirabilis urease: nucleotide sequence determination and comparison with jack bean urease. 268 33

Six Angus heifer calves (234 kg) were assigned to either a high (HP; 126.1 g N/d) or low (LP; 66.5 g N/d) protein intake to evaluate ruminal criteria associated with movement of blood urea-N (BUN)-derived NH3-N from the rumen wall into interior ruminal digesta. Calves received 4.8 kg DM/d of diets containing 30% cottonseed hulls and 70% cornsoybean meal in equal portions at 4-h intervals. Following single i.v. injections of 15N-urea, ruminal fluid was collected serially for 4 h postinjection from digesta located adjacent to the rumen wall (wall-proximate digesta; WPD) and from the center of the rumen digesta mass after manual agitation (center mixed digesta; CMD). Mean ruminal NH3-N (RAN) concentrations were higher (P less than .05) for HP than for LP, but were not affected (P greater than .05) by digesta sampling site. Ruminal urease activity was higher (P less than .05) for LP than for HP and tended (P = .14) to be higher for WPD than for CMD. Area under the 15N enrichment curve (AUC) ratios between sampling sites (WPD/CMD x 100) for RAN were greater (P less than .05) for LP than for HP. However, AUC ratios for bacterial N were not affected (P greater than .05) by protein level. Whereas BUN-derived 15NH3 appeared to thoroughly equilibrate with RAN in interior ruminal digesta with HP, there appeared to be a declining enrichment gradient for RAN from the rumen wall to the interior ruminal digesta with LP. Data are interpreted to suggest that bacteria at or near the rumen wall may preferentially utilize some BUN-derived NH3-N entering through the rumen wall in calves fed LP diets.
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PMID:Effect of dietary protein level on nitrogen metabolism in the growing bovine: II. Diffusion into and utilization of endogenous urea nitrogen in the rumen. 272 10

Increased brain and plasma glutamine after ammonia inhalation had an effect on the concentrations of selected amino acids in rats. Rats inhaled ammonia vapour of 25 and 300 p.p.m. for 5 days 6 hr daily. Brain glutamine increased from the control level, 10.9 +/- 2.6 (S.D.) mumol/g to 15.5 +/- 5.2 (S.D.) mumol/g (P less than 0.05) in 25 p.p.m. NH3 and to 15.3 +/- 1.1 (S.D.) mumol/g (P less than 0.01) in 300 p.p.m. NH3. The blood glutamine was also increased so that the brain/plasma ratio was not changed. A slight elevation in the brain threonine was found, from 0.6 +/- 0.1 (S.D.) mumol/g (controls) to 0.8 +/- 0.2 (S.D.) mumol/g in 25 p.p.m. and to 0.8 +/- 0.1 (S.D.) mumol/g in 300 p.p.m. NH3. The brain/plasma ratio of threonine was increased at the 300 p.p.m. level. The increasing brain threonine linearly correlated to the increased plasma glutamine the general correlation co-efficient being 0.59 according to a linear regression analysis. The effects on other amino acids, e.g., glycine, alanine, serine, aspartate, glutamate, were less clear. It seems that the elevated blood glutamine impaired the threonine export or augmented its uptake from the blood stream. Exposure to NH3 vapour by inhalation proved to be an alternative model to portocaval shunting or urease injections in the study of hyperammonemia in the brain.
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PMID:Effect of short-term ammonia inhalation on selected amino acids in rat brain. 272 87

The effects of oral and intraperitoneal administration of biotin in urease-induced hyperammonemic rats, as well as the influence of biotin deficiency, have been studied. Biotin deficiency was produced by feeding standard diet MF (Oriental Yeast Co.) supplemented with dry egg-white (egg-white group). Egg-white + biotin group had free access to 0.0014% of biotin solution at all time. Following an intraperitoneal injection of urease, 25 U/kg (B.W.), plasma ammonia levels in egg-white + biotin group were lower than in egg-white group, especially there was significance (p less than 0.05) at 8 hours after the urease injection. Similarly, plasma ammonia levels in biotin-injected rats, in which 1 mg of biotin had been injected intraperitoneally prior to the experiment, were significantly low compared with saline-injected controls at 4 and 6 hours after urease administration. Results of plasma amino acid analysis, 9 hours after the urease injection indicated that Fischer's molar ratio (Leu + Ileu + Val/Tyr + Phe) was significantly higher in the biotin-injected rats than the saline-injected control. It suggests that biotin might decrease blood ammonia by facilitating the detoxification mechanism as follow: L-glutamate + NH3----L-glutamine.
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PMID:[The effects of biotin on the metabolism of ammonia and amino acids in urease-induced hyperammonemic rats]. 281 Aug 55

Proteus mirabilis, a cause of serious urinary tract infection, produces urease, an important virulence factor for this species. The enzyme hydrolyzes urea to CO2 and NH3, which initiates struvite or apatite stone formation. Genes encoding urease were localized on a P. mirabilis chromosomal DNA gene bank clone in Escherichia coli by deletion analysis, subcloning, Bal31 nuclease digestion, transposon Tn5 mutagenesis, and in vitro transcription-translation. A region of DNA between 4.0 and 5.4 kilobases (kb) in length was necessary for urease activity and was located within an 18.5-kb EcoRI fragment. The operon was induced by urea and encoded a multimeric, cytoplasmic enzyme comprising subunit polypeptides of 8,000, 10,000, and 73,000 daltons that were encoded by a single polycistronic mRNA and transcribed in that order. Seventeen urease-negative transposon insertions were isolated that synthesized either none of the structural subunit polypeptides, the 8,000-dalton polypeptide alone, or both the 8,000- and 10,000-dalton subunit polypeptides. The molecular weight of the native enzyme was estimated to be 212,000 by Superose-6 chromatography. Homologous sequences encoding the urease of Providencia stuartii synthesized subunit polypeptides of similar sizes and showed a similar genetic arrangement. However, restriction maps of the operons from the two species were distinct, indicating significant divergence.
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PMID:Proteus mirabilis urease: genetic organization, regulation, and expression of structural genes. 284 Dec 83


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