Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:6.3.4.6 (urease)
 7,490 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Helicobacter pylori infection is associated with gastric mucosal damage and the infiltration of neutrophils. Myeloperoxidase from neutrophils produces hypochlorous acid, which yields monochloramine in the presence of ammonia produced by urease enzyme of Helicobacter pylori. The target cells of gastric mucosal damage are gastric mucosal cells and endothelial cells. We therefore tested the hypothesis that ammonium, hypochlorous acid, and monochloramine damage the target cells. We studied the in vitro cytotoxic effects of ammonium chloride, sodium hypochlorite, monochloramine, and activated neutrophils on the target cells. Cytotoxicity was measured by a 51Cr-release assay. Ammonium chloride, sodium hypochlorite, and monochloramine were toxic to labeled cells in a concentration dependent manner. The toxicity of these agents was in the order monochloramine > sodium hypochlorite >> ammonium chloride. Incubation of labeled cells with activated neutrophils, Helicobacter pylori, and urea resulted in cytolysis. These cytotoxicities were significantly inhibited by the scavenger of hypochlorous acid, taurine. Monochloramine is more toxic to the target cells than ammonium chloride. Although ammonium chloride at neutral pH by itself has little direct damaging effect on the gastric mucosa, it is damaging to the gastric mucosa through a reaction with hypochlorous acid, suggesting that it plays a role in Helicobacter pylori-associated gastric damage.
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PMID:Mechanism of Helicobacter pylori-associated gastric mucosal injury. 778 56

Different concentrations either of ammonium chloride or urea were used in batch and fed-batch cultivations of Spirulina platensis to evaluate the possibility of substituting nitrate by cheaper reduced nitrogen sources in wastewaters biotreatment. The maximum nitrogen concentration able to sustain the batch growth of this microalga without inhibition was 1.7 mM in both cases. Ammonium chloride was limiting for the growth at lower concentrations, whereas inhibition took place at higher levels. This inhibition effect was less marked with urea, likely because the enzymatic hydrolysis of this compound by urease controlled the ammonia transfer into the cell. Fed-batch experiments carried out by pulse-feeding either ammonium or urea proved that the use of these compounds as nitrogen sources can sustain the long term-cultivation of S. platensis, provided that the conditions for their feeding are accurately optimized.
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PMID:Ammonium and urea removal by Spirulina platensis. 1617 8