Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.1.3 (ATPase)
 65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Ureaplasma urealyticum cells were lysed by osmotic shock or by digitonin. The membrane fraction contained four to ten times as much protein as the cytoplasmic fraction. These values are in large excess of those reported for classical mycoplasmas, suggesting that the Ureaplasma membrane fraction was heavily contaminated with proteins derived from the growth medium. The U. urealyticum urease activity was localized in the cytoplasmic fraction, whereas the adenosine triphosphatase activity was localized in the membrane fraction. Significant urease activity could be detected also in nonviable cells. Urea, at concentrations above 0.25 M, was mycoplasmastatic to Acholeplasma laidlawii, Mycoplasma hominis, and U. urealyticum, so that the Ureaplasma urease did not afford preferential protection against urea toxicity. The intracellular localization of the urease would be expected to release ammonia from urea in the cytoplasm. The ammonia will take up protons to become ammonium ions. It can be hypothesized that the intracellular NH4+ plays a role in proton elimination or acid-base balance, which might be coupled to an energy producing ion gradient and/or transport mechanisms.
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PMID:Localization of enzymes in Ureaplasma urealyticum (T-strain mycoplasma). 1 80

The localization of some enzymic activities in cell fractions of Ureaplasma urealyticum was studied. A quantitative evaluation of the effectiveness of several cell lysis procedures was obtained by using labeled membranes and sucrose density gradient centrifugation. Ultrasonic treatment was found to be the most effective procedure for lysing the cells, whereas digitonin and osmotic shock caused the lysis of only 70 and 50% of the cells, respectively. The localization of selected enzymes in Ureaplasma cells resembled that found in other Mycoplasma species. Adenosine triphosphatase, ribonuclease, deoxyribonuclease, and p-nitrophenylphosphatase activities were located exclusively in the membrane fraction, whereas urease and L-histidine ammonia-lyase were located in the cytoplasm.
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PMID:Cell fractions and enzymatic activities of Ureaplasma urealyticum. 21 22

Ureaplasma urealyticum lacks the conventional mechanisms for adenosine 5-triphosphate (ATP) generation, such as glycolysis or arginine breakdown, present in other mycoplasmas. The possibility that ATP may be generated in these organisms through the formation of an ion gradient coupled to urea hydrolysis has been suggested by Masover and Hayflick (Ann NY Acad Sci 225:118-130, 1973). Our data have proved that ATP is produced when urea is added to resting ureaplasmal cells and its formation requires the concomitant activity of both cytoplasmic urease and membrane-bound ATPase and is drastically reduced by carbonylcyanide-m-chlorophenylhydrazine. Analysis of the optimal conditions for ATP synthesis in ureaplasmas indicates that this energetic process depends upon phosphate, urea, pH and ammonium ions in the reaction mixture. Particularly ammonium ions can interfere with the production of energy only when the starting pH is kept slightly basic. We have also shown that the changes in fluorescence intensity are directly related to the concentrations of the added urea and are inhibited by the presence of acetohydroxamic acid, carbonycyanide-m-chlorophenylhydrazine, and ammonium ions. It appears that urea hydrolysis can generate an electrical potential through NH4+ diffusion across the Ureaplasma membranes, but this diffusion is also dependent upon the external acidic pH of the reaction mixture.
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PMID:Energy production in Ureaplasma urealyticum. 379 30

Based on clinical studies, a negative association between Helicobacter pylori and autoimmune corpus gastritis is described. In the present investigation of an unselected population of 1461 adults we can state, however, that there exists a relationship between H. pylori infection and the development of gastric corpus autoimmunity. As confirmation for the gastric autoantibody development through molecular mimicry, a high homology (72% in 25 amino acid overlap) between the beta subunit of H. pylori urease and that of H + K + ATPase, the gastric parietal cell autoantigen, was revealed.
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PMID:Association of Helicobacter pylori and gastric autoimmunity: a population-based study. 759 5

The nucleotide sequence of the amidase operon of Pseudomonas aeruginosa has been completed and two new genes identified amiB and amiS. The complete gene order for the operon is thus amiEBCRS. The amiB gene encodes a 42-kDa protein containing an ATP binding motif that shares extensive homology with the Clp family of proteins and also to an open reading frame adjacent to the amidase gene from Rhodococcus erythropolis. Deletion of the amiB gene has no apparent effect on inducible amidase expression and it is thus unlikely to encode a regulatory protein. A maltose-binding protein-AmiB fusion has been purified and shown to have an intrinsic ATPase activity (Km = 174 +/- 15 mM; Vmax = 2.4 +/- 0.1 mM/min/mg), which is effectively inhibited by ammonium vanadate and ADP. The amiS gene encodes an 18-kDa protein with a high content of hydrophobic residues. Hydropathy analysis suggests the presence of six transmembrane helices in this protein. The AmiS sequences is homologous to an open reading frame identified adjacent to the amidase gene from Mycobacterium smegmatis and to the ureI gene from the urease operon of Helicobacter pylori. AmiS and its homologs appear to be a novel family of integral membrane proteins. Together AmiB and AmiS resemble two components of an ABC transporter system.
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PMID:Identification of two new genes in the Pseudomonas aeruginosa amidase operon, encoding an ATPase (AmiB) and a putative integral membrane protein (AmiS). 764 33

Inhibition of the Na+/K(+)-ATPase by a circulating endogenous digitalis- or ouabain-like substance has been associated with the pathogenesis of several forms of clinical and experimental hypertension. Inbred salt-sensitive Dahl SS/jr rats were immunized with either urease or a ouabain-urease conjugate, then challenged with a high salt diet. The salt-induced increase in blood pressure in the ouabain-urease-immunized animals was significantly less than that of the urease-inoculated rats. Sera of the ouabain-urease immunized animals cross-reacted with ouabagenin, digoxigenin, digoxin, and digitoxin, but not with aldosterone, corticosterone, deoxycorticosterone (DOC), 18-hydroxy DOC, or 19-nor DOC. The fact that hypertension was not completely blocked by immunization supports ample evidence that the disease in these animals is multifactorial with several genes involved.
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PMID:Immunization of Dahl SS/jr rats with an ouabain conjugate mitigates hypertension. 794 59

Helicobacter pylori urease belongs to a family of highly conserved urea-hydrolyzing enzymes. A common feature of these enzymes is the presence of two Lewis acid nickel ions and a reactive cysteine residue in the active site. The H+/K(+)-ATPase inhibitor omeprazole is a prodrug of a sulfenamide which covalently modifies cysteine residues on the luminal side of the H+/K(+)-ATPase of gastric parietal cells. Omeprazole and eight analogues were selected based on their chemical, electronic, and kinetic properties, and each was incubated with viable H. pylori in phosphate-buffered saline at pH 7.4 for 30 min, after which 100 mM urea was added and the amount of ammonia formed analyzed after a further 10 min. Inhibition between 0% and 100% at a 0.1 mM concentration was observed for the different analogues and could be expressed as a function of the pKa-value of the pyridine, the pKa-value of the benzimidazole, the overall lipophilicity, and, most importantly, the rate of sulfenamide formation, in a quantitative structure-activity relationship. The inhibition was potentiated by a lower pH (favoring the formation of the sulfenamide) but abolished in the presence of beta-mercaptoethanol (a scavenger of the sulfenamide). Structural analogues incapable of yielding the sulfenamide did not inhibit ammonia production. Treatment of Helicobacter felis-infected mice with 230 mumol/kg flurofamide b.i.d. for 4 weeks, known to potently inhibit urease activity in vivo, as a means of eradicating the infection, was tested and compared with the effect of 125 mumol/kg omeprazole b.i.d. for 4 weeks. Neither treatment proved efficacious.
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PMID:Structure-activity relationship of omeprazole and analogues as Helicobacter pylori urease inhibitors. 852 4

Helicobacter pylori is highly adapted to its unusual ecological niche in the human stomach. Urease activity permits H. pylori survival at a pH of <4 in vitro and is required for the organism to colonize in animal models. However, urease does not play an important role in the survival of the organism in a pH range between 4 and 7. Other mechanisms of pH homeostasis remain poorly understood, but preliminary studies indicate that novel proteins are produced when H.pylori cells are shifted from pH 7 to 3, and the gene encoding a P-type adenosine triphosphatase that may catalyze NH4+/H+ exchange across the cytoplasmic membrane has been cloned. Mechanisms of pH homeostasis in other enteric bacteria are reviewed and provide insight into additional pathways that may be used by H. pylori. An important adaptation of H. pylori to the gastric environment may be its ability to alter gastric acid secretion. Acute infection is associated with transient hypochlorhydria, whereas chronic infection is associated with hypergastrinemia and decreased somatostatin levels. Thus, the survival of H. pylori in the gastric environment may be attributed to both the development of specialized intrinsic defenses and the organism's ability to induce physiological alterations in the host environment.
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PMID:Helicobacter pylori and gastric acid: biological and therapeutic implications. 878 Jun

The anti-ulcer drugs that act as covalent inhibitors of the gastric acid pump are targeted to the gastric H+/K+ ATPase by virtue of accumulation in acid and conversion to the active sulfenamide. This results in extremely effective inhibition of acid secretion. Appropriate dosage is able to optimize acid control therapy for reflux and peptic ulcer disease as compared to H2 receptor antagonists. However, clinical data on recurrence show that Helicobacter pylori eradication should accompany treatment of the lesion. These drugs have been found to synergize with many antibiotics for eradication. The survival of aerobes depends on their ability to maintain a driving force for protons across their inner membrane, the sum of a pH and potential difference gradient, the protonmotive force (pmf). The transmembrane flux of protons across the F1F0 ATPase, driven by the pmf, is coupled to the synthesis of ATP. The internal pH of H. pylori was measured using the fluorescent dye probe, BCECF, and the membrane potential defined by the uptake of the carbocyanine dye, DiSC3 [5] at different pHs to mimic the gastric environment. The protonmotive force at pH 7.0 was composed of a delta pH of 1.4 (-84mV) and a delta potential difference of -131mV, to give a pmf of -215 mV. The effect of variations in external pH on survival of the bacteria in the absence of urea correlated with the effect of external pH on the ability of the bacteria to maintain a pmf. The effect of the addition of 5 mM urea on the pmf was measured at different medium pH values. Urea restored the pmf at pH 3.0 or 3.5, but abolished the pmf at pH 7.0 or higher, due the production of the alkalinizing cation, NH3. Hence H. pylori is an acid-tolerant neutrophile due to urease activity, but urease activity also limits its survival to an acidic environment. These data help explain the occupation of the stomach by the organism and its distribution between fundus and antrum. This distribution and its alteration by proton pump inhibitors also explains the synergism of proton pump inhibition and antibiotics such as amoxicillin and clarithromycin in H. pylori eradication.
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PMID:Acid, protons and Helicobacter pylori. 916 99

An automatic enzyme kinetic luminometric method for determination of small quantities of urea in biological fluids and in microdialysates is presented. The method is based on the ATP-hydrolyzing urease reaction [urea amidohydrolase (ATP-hydrolyzing); EC 3.5.1.45], monitored by a luciferin-luciferase ATP reaction. The assay range is 100 pmol to 50 nmol with a detection limit of 5 micromol/L in the sample, compared with detection limits of 0.1 mmol/L in earlier spectrophotometric methods. To reduce the non-urea-dependent ATPase activity (v(blank)) and to increase the urea-dependent activity, 1,2-propanediol was included. Assay conditions were optimized by multivariate analysis. Recoveries of urea added to blood dialysate and plasma were 96-103%. No analytical interference of common metabolites, drugs, or other additives was observed. The total CVs (6 days and six concentrations, 1.2-21.8 mmol/L) were 3.6-8.5%. The results obtained with the present assay were highly correlated for dialysate (r = 0.979) and for plasma (r = 0.978) with those obtained by a spectrophotometric kit method with slopes of 1.02-1.03 and intercepts of 0.08-0.23 mmol/L.
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PMID:Luminometric single step urea assay using ATP-hydrolyzing urease. 973 85


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