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)

Urea production from arginine was studied in vitro in the kidney of normal rats in tubule suspensions of the four different renal zones (cortex, outer and inner stripe of outer medulla, and inner medulla), and in individual microdissected nephron segments. Tissue was incubated with L-[guanido-14C]-arginine to measure cellular arginase activity. Addition of urease to the incubate freed 14CO2 from the 14C-urea formed by arginase and released from the cells. CO2 was trapped in KOH and counted. These experiments revealed that significant amounts of urea are produced in the outer stripe and in the inner medulla. This intrarenal urea generation takes place mainly in the proximal straight tubule and in the collecting duct, with increasing activity in these two structures from superficial to deep regions of the kidney. Urea is known to play a critical role in the urinary concentrating process. The fact that some urea can be produced in the mammalian kidney, and that the two structures showing this capacity are straight portions of the renal tubular system descending along the corticopapillary axis suggest that this urea production might play a role in the formation and/or maintenance of the medullary urea concentration gradient.
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PMID:Production of urea from arginine in pars recta and collecting duct of the rat kidney. 251 52

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

Campylobacter pylori is a bacterium which has been suggested as a causative agent in active chronic gastritis and possibly peptic ulcer disease. The diagnosis has had to be made by culture or histological examination of gastric mucosal biopsies. Since endoscopy is needed to obtain biopsies, this precludes large-scale epidemiological studies of this organism. Recently Graham described a noninvasive breath test with carbon 13 labelled urea to detect C. pylori colonization. This breath test is based on our finding of the remarkably high urease activity of C. pylori. Ingested labelled urea will be rapidly broken down in the stomach if urease activity, and so C. pylori, is present. Breath samples are collected at 10-minute intervals and analysis from these samples for labelled CO2 content is then made. In the present paper we describe current experience with the 13C- and 14C-urea breath test.
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PMID:Detecting Campylobacter pylori with the 13C- and 14C-urea breath test. 281 46

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

The high endogenous urease activity of Campylobacter pylori was exploited in a non-invasive test for the presence of this organism in the stomach. When 13C-urea was administered orally after a test meal, urea-derived 13CO2 appeared in the respiratory CO2 of infected individuals at a constant rate for greater than 100 min. The test was validated in 26 individuals who underwent both the 13C-urea breath test and endoscopic biopsy of the antral mucosa for culture and histological examination. Each positive breath test proved to be correlated with a positive culture or Warthin-Starry silver stain of a mucosal biopsy specimen, or both.
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PMID:Campylobacter pylori detected noninvasively by the 13C-urea breath test. 288 91

The detrimental effects of excessive Ni on plant growth have been well known for many years. More recent evidence indicates that Ni is required in small amounts for normal plant growth and development. Ni is an essential component of urease in plants and microorganisms. A deficiency of Ni in plants is reported to result in necrotic lesions in leaves in response to toxic accumulations of urea. Urease plays an essential role in mobilization of nitrogenous compounds in plants, a process that is especially important during seed germination and fruit formation when protein reserves are degraded into amino acids. Arginine, an abundant amino acid in plants, when degraded produces urea as a product and urease is needed for urea utilization. Theories of urea formation during allantoin degradation in Glycine max have been recently refuted. In G. max ureides apparently are metabolized via an amidohydrolase reaction with subsequent degradation of ureidoglycine, yielding glyoxylate, NH+4 and CO2. No evidence is available for the formation of urea in this pathway. Nitrogen-fixing symbionts, such as Rhizobium and Bradyrhizobium, contain two known Ni enzymes: urease and hydrogenase. Optimum growth of nodulated legumes and actinorhizal plants may depend on an adequate supply of Ni to meet the requirements of the Ni-requiring enzymes in host plants and endophytes. The seeds of severely Ni-deficient Hordeum are completely inviable, thus providing conclusive evidence for the essentiality of Ni for this species. The evidence indicates that Ni must be added to the list of micronutrient elements generally required by plants.
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PMID:Nickel as a micronutrient element for plants. 307 27

The comparative study of 44 isolates of Corynebacterium group D2, from urine, most frequently, shows the pathogenic role of these bacteria in urinary tract infection, with or without urinary stones. These microorganisms have an opportunistic behaviour in other non-urinary sites, and become pathogen in immunosuppressed conditions. The rapid tests as urease, glucose acidification, nitrate reductase, associated with multiple resistance to antibiotics (beta-lactams and aminosides) identify easily Corynebacterium group D2, from 48 h cultures under CO2 conditions. The results of MIC determination of 10 antibiotics, show the high activity (100% sensitivity) of vancomycin and pristinamycin, with MIC modes, respectively, 0.5 and 0.03 mg/l. These antibiotics are the most useful for the treatment of non-urinary infections. Among quinolones, the most active agents are ciprofloxacin and ofloxacin (MIC modes: 4 and 2 mg/l), so these antimicrobials could be used for the treatment of urinary tract infections caused by Corynebacterium group D2.
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PMID:[Corynebacterium group D2. Clinical study, biochemical identification and antibiotic sensitivity]. 313 26

Urease in the human gastric mucosa is a marker for infection with Campylobacter pylori (CP), an organism suspected of causing chronic gastritis and peptic ulceration. To detect gastric urease, we examined 32 patients who were being evaluated for possible peptic ulcer disease. Fasting patients were given 10 microCi (370 kBq) of 14C-labeled urea. Breath samples were collected in hyamine at intervals between 1 and 30 min. The amount of 14C collected at these times was expressed as: body weight X (% of administered dose of 14C in sample)/(mmol of CO2 collected). The presence of C. pylori colonization was also determined by examination of multiple endoscopic gastric biopsy specimens. On average, patients who were proven to have C. pylori infection exhaled 20 times more labeled CO2 than patients who were not infected. The difference between infected patients and C. pylori negative "control" patients was highly significant at all time points between 2 and 30 min after ingestion of the radionuclide (p less than 0.0001). The noninvasive urea breath is less expensive than endoscopic biopsy of the stomach and more accurate than serology as a means of detecting Campylobacter pylori infection. Because the test detects actual viable CP organisms, it can be used to confirm eradication of the bacterium after antibacterial therapy.
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PMID:Carbon-14 urea breath test for the diagnosis of Campylobacter pylori associated gastritis. 333 17

A rapid, simple and inexpensive procedure for the determination of urease activity by using a thermal conductivity gas chromatography method is presented. The procedure is based on the determination of CO2 released in the urease reaction, and showed low coefficient of variation (c.v. less than 1%) and high sensitivity (detection limit 10(-12) mol). This procedure is also suitable for determination of other decarboxylating enzyme activities.
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PMID:Determination of urease activity by thermal conductivity gas chromatography. 377 25

In a non-recirculating system of isolated liver perfusion, stimulation of urea synthesis by NH4Cl is followed by a decrease of effluent pH by up to 0.2 pH unit. This effect is not observed when urea synthesis is inhibited by amino-oxyacetate or norvaline. When the urea formed by the liver is immediately hydrolysed with urease before the effluent perfusate reaches the pH electrode, the urea-synthesis-induced acidification is no longer observed. This indicates that accompanying alterations in hepatic metabolism after stimulation of urea synthesis, such as increased energy provision and consumption, are not responsible for the extracellular acidification, but that the effect is due to the formation of urea itself. The acidification of the extracellular space after stimulation of urea synthesis by NH4Cl is quantitatively explained by the consumption of 2 mol of HCO3-/mol of urea formed: 1 mol being incorporated into urea, the other being protonated to yield CO2 and H2O. The data match the theoretically predicted HCO3- consumption during ureogenesis and underline the role of hepatic urea synthesis for disposal of HCO3- by converting it into the excretable products CO2 and urea.
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PMID:The effect of urea synthesis on extracellular pH in isolated perfused rat liver. 379 75


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