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Complications Related to Neurogenic Bladder Dysfunction I
Published in Jacques Corcos, Gilles Karsenty, Thomas Kessler, David Ginsberg, Essentials of the Adult Neurogenic Bladder, 2020
The bacteria that produce urease are particularly harmful because of significant alkalinization of urine, which promotes the precipitation of struvite stone (magnesium-ammonium-phosphate and calcium carbonate). The most common organism associated with struvite calculi is Proteus mirabilis. Other organisms include Ureaplasma urealyticum, Providencia stuartii, Yersinia enterocolitica, and Bacteroides corrodens.12,13
Introduction to hyperammonemia and disorders of the urea cycle
Published in William L. Nyhan, Georg F. Hoffmann, Aida I. Al-Aqeel, Bruce A. Barshop, Atlas of Inherited Metabolic Diseases, 2020
William L. Nyhan, Georg F. Hoffmann, Aida I. Al-Aqeel, Bruce A. Barshop
In older children and adults, a number of acquired disorders can also present with hyperammonemia, including liver disease, Reye syndrome, drug toxicity, and hepatotoxin ingestion. History, prothrombin time, a urinary toxic screen, and plasma amino acid pattern should help to differentiate these disorders. Symptomatic hyperammonemia may also result from a urinary tract infection in which the infecting Proteus mirabilis has urease activity, which produces ammonia from urea. A patient with prune-belly syndrome and massive dilatation of the urinary tract developed coma with a blood concentration of ammonia of 140 μmol/L (202 μg/dL).
Helicobacter pylori infection
Published in Phillip D. Smith, Richard S. Blumberg, Thomas T. MacDonald, Principles of Mucosal Immunology, 2020
Diane Bimczok, Anne Müller, Phillip D. Smith
Expressed by all strains, H. pylori urease is essential for establishing and maintaining bacterial colonization in the acidic environment of the stomach by hydrolyzing urea into carbon dioxide and ammonia (NH3), which neutralizes gastric acid. The pH change induced by urease activity also reduces the viscosity of gastric mucus, promoting bacterial motility. At the epithelial surface, the released ammonia may disrupt tight junctions, thereby damaging the epithelial barrier. In addition to its enzymatic function, urease mediates bacterial adhesion to the gastric epithelium and serves as a chemotactic factor for monocytes and neutrophils. Urease also can directly damage host cells, especially antigen-presenting and epithelial cells, by triggering apoptosis through a major histocompatibility complex (MHC)-II-dependent mechanism. Urease is an immunodominant antigen, with 25% of T-cell clones in infected subjects having specificity for urease epitopes. Consequently, many vaccine constructs currently being developed include urease as a major vaccine antigen.
An overview: metal-based inhibitors of urease
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2023
Wei Yang, Zhiyun Peng, Guangcheng Wang
Urease (EC 3.5.1.5, urea amide hydrolase) is a natural enzyme strictly dependent on the metal ion nickel, widely distributed in fungi, bacteria, algae, plants, and other species 1,2. Besides, urease can catalyse the hydrolysis of urea to form carbamic acid and ammonia 3,4. In 1995, the first complete structures of three-dimensional urease have been reported via the crystallographic study of Klebsiella aerogenes urease5. Since then, the researchers have elucidated other structures of ureases from Canavalia ensiformis6, Pasteurella7, and Helicobacter pylori (H. pylori)8. Moreover, the structure of urease contains heteromeric molecules with three subunits α, β, and γ9, and the active site of urease is located in the α subunit, which has two Ni2+ (Ni1 and Ni2) centres10. Additionally, these two nickel ions are essential in the general mechanism of catalysis by urease7. One of the nickel ions is responsible for binding and activating urea, while the other binds and activates nucleophilic water molecules7. When the water molecules are replaced, the N atom of amino on the urea combines with Ni2, which promotes the release of NH3 and carbamate7.
Integrated hypothesis of dental caries and periodontal diseases
Published in Journal of Oral Microbiology, 2020
Bente Nyvad, Nobuhiro Takahashi
Some common bacteria in the supragingival plaque, such as Actinomyces and Streptococcus, possess urease [16], which quickly breaks down urea into ammonia and carbon dioxide, and neutralizes bacteria-derived acids. Bacterial urease can function at a wide range of pH while keeping high activity at acid pH [57]. Other metabolic pathways, such as bacterial amino acid fermentation, the arginine/agmatine deiminase system and amino acid decarboxylation are also known to neutralize environmental pH (Figure 2) [16]. In addition, bacteria-derived acids can be degraded or converted into weaker acids via lactate degradation, formate degradation, malolactic reaction, and acid conversion (Figure 2) [16]. These acidification and acid-neutralization/alkalization processes that occur repeatedly in the supragingival plaque counteract each other and limit major pH-fluctuations exceeding the 5.5–7 range between meals.
Amelioration of Diabetes-Induced Diabetic Nephropathy by Aloe vera: Implication of Oxidative Stress and Hyperlipidemia
Published in Journal of Dietary Supplements, 2019
Mandeep Kumar Arora, Yogesh Sarup, Ritu Tomar, Mary Singh, Puspendra Kumar
The blood urea was estimated by Berthelot method (Fawcett & Scott, 1960) using the commercially available kit (ERBA, Transasia Bio-Medicals Ltd., Solan, India). The amount of 1,000 µl of working reagent-I containing urease reagent, and a mixture of salicylate, hypochlorite, and nitroprusside was added to 10 µl of serum, 10 µl of standard urea (40 mg/dl), and 10 µl of purified water to prepare test, standard, and blank, respectively. All test tubes were mixed well and incubated at 37°C for 5 min. Then 1,000 µl of reagent-II containing alkaline buffer was added to all the test tubes, which were incubated at 37°C for 5 min. Urease catalyzes the conversion of urea to ammonia and carbon dioxide. The ammonia thus released reacts with a mixture of salicylate, hypochlorite, and nitroprusside to yield indophenol, a blue-green–colored compound. The intensity of the color produced is directly proportional to the concentration of urea in the sample and is measured spectrophotometrically at 578 nm. The blood urea was calculated using the following formula: