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)

1. Citrate isocitrate and 2-oxoglutarate levels were determined in isolated rat hepatocytes and in particulate and soluble fractions, thereof, obtained by the digitonin and silicone oil fractionation technique. 2. Caculated from isocitrate/2-oxoglutarate ratios ("indicator metabolite method"), the redox potential of mitochondrial free NADPH is -402 mV, whereas that of the extramitochondrial (cytosolic) space is about 10 mV more positive, -392 mV. 3; Addition of ammonia (either as ammonium chloride or from urea plus urease) to isolated hepatocytes causes preferential oxidation of mitochondrial NADPH, is demonstrated by spectrophotometry of the dihydro band and by the changes in the isocitrate/2-oxoglutarate ratios. The redox potential difference of free NADPH between mitochondria and cytosol is abolished or even reserved. 4. It is concluded that during urogenesis from ammonia mitochondrial isocitrate oxidation is shifted largely in favor of the NADP-linked as opposed to the NAD-linked enzyme; isocitrate concentration under these conditions is less than 10 muM, below the Km (isocitrate) of the NAD-linked enzyme but in the range of that for the NADP-linked enzyme. 5. Both in the absence and in the presence of ammonia there is a concentration gradient across the mitochondrial inner membrane (from mitochondria to cytosol) for citrate, isocitrate, and also, to a smaller extent, for 2-oxoglutarate. 6. These results and data in the literature on enzyme activity are in agreement with the assumption of near-equilibrium of NADP-dependent isocitrate dehydrogenases in the mitochondrial matrix and cytosolic spaces in the absence of ammonia; accordingly, during urea formation from added ammonia the redox potential of mitochondrial free NADPH is increased to -391 mV or possibly even higher if there exists an indicator error under this condition.
 ...
PMID:Mitochondrial and cytosolic NADPH systems and isocitrate dehydrogenase indicator metabolites during ureogensis from ammonia in isolated rat hepatocytes. 1 98

Succinivibrio dextrinosolvens C18 was found to possess glutamine synthetase (GS), urease, glutamate dehydrogenase, and several other nitrogen assimilation enzymes. When grown in continuous culture under ammonia limitation, both GS and urease activities were high and glutamate dehydrogenase activity was low, but the opposite activity pattern was observed for growth in the presence of ample ammonia. The addition of high-level (15 mM) ammonium chloride to ammonia-limited cultures resulted in a rapid loss of GS activity as measured by either the gamma-glutamyl transferase or forward assay method with cells or extracts. No similar activity losses occurred for urease, glutamate dehydrogenase, or pyruvate kinase. The GS activity loss was not prevented by the addition of chloramphenicol and rifampin. The GS activity could be recovered by washing or incubating cells in buffer or by the addition of snake venom phosphodiesterase to cell extracts. Manganese inhibited the GS activity (forward assay) of untreated cells but stimulated the GS activity in ammonia-treated cells. Alanine, glycine, and possibly serine were inhibitory to GS activity. Optimal pH values for GS activity were 7.3 and 7.4 for the forward and gamma-glutamyl transferase assays, respectively. The glutamate dehydrogenase activity was NADPH linked and optimal in the presence of KCl. The data are consistent with an adenylylation-deadenylylation control mechanism for GS activity in S. dextrinosolvens, and the GS pathway is a major route for ammonia assimilation under low environmental ammonia levels. The rapid regulation of the ATP-requiring GS activity may be of ecological importance to this strictly anaerobic ruminal bacterium.
 ...
PMID:Glutamine synthetase activity in the ruminal bacterium Succinivibrio dextrinosolvens. 286 38

A spectrophotometric method for the determination of arginase (EC 3.5.3.1) is presented. Arginase is coupled to urease and glutamate dehydrogenase and the decrease in absorbance at 340 nm due to the oxidation of NADPH is followed. The method is rapid, is sensitive, is economical and permits continuous monitoring. The initial velocities were directly proportional to the enzyme concentrations between 0.06 and 0.30 units per 0.5 ml. The Lineweaver-Burk plot yielded positive allosteric behavior for the tetrameric enzyme. The K' and the Hill coefficient, n, calculated from Hill plot were found to be 4.7 mM and 1.26 (r = 1.00), respectively. These values are in good agreement with the literature.
 ...
PMID:A new enzyme-coupled spectrophotometric method for the determination of arginase activity. 401 34

A two-step method for assaying creatinine in serum and urine samples, suitable with automated analyzers, is reported. Reagent 1, for the first step, contains a blanking system [creatine amidinohydrolase (CRTase), urease, glutamate dehydrogenase, NADPH, and 2-oxoglutarate] and a NADPH-regenerating system [Mg(2+)-dependent isocitrate dehydrogenase (ICD), MgCl2, and excess isocitrate]. Reagent 2, for the second step, contains the metal-chelating reagent trans-1,2-cyclohexanediamine-N,N,N',N'-tetraacetic acid (CyDTA) and a trigger system [creatinine amidohydrolase (CRNase)]. When a specimen is mixed with reagent 1, all the creatine, urea, and NH3 present are removed by the blanking and NADPH systems. On adding reagent 2, CyDTA inactivates ICD to inhibit the NADPH system. Simultaneously, the creatinine (1 mol) in the specimen is hydrolyzed into creatine by CRNase, and then releases NADP+ (2 mol) through the blanking system. Our optimized method can determine creatinine linearly up to 500 mg/L, with within-day CVs < 1.2% and day-to-day CVs < 2.7%.
 ...
PMID:Enzymatic rate assay of creatinine in serum and urine. 840 98

We established a simple and rapid kinetic assay for measurement of calcium in serum by using urea amidolyase (EC 3.5.1.45) from yeast species. The method is based on inhibition of the enzyme by calcium. In the assay, we eliminated endogenous ammonium ion by use of glutamate dehydrogenase (GLDH; EC 1.4.1.4); then in the presence of urea amidolyase, urea, ATP, bicarbonate, magnesium, and potassium ions, ammonium ion production was inversely proportional to calcium ion concentration in serum. The concentration of ammonium ion formed was determined by adding GLDH to produce NADP+ in the presence of 2-oxoglutarate and NADPH; we then monitored the change of absorbance at 340 nm. The within-run CVs of this method were 1.7-3.2% (n = 10) at 1.53-3.08 mmol/L, respectively. Day-to-day (total) CVs were 2.8-4.1%. Analytical recovery was 92-112%. The presence of other ions, ascorbic acid, reduced glutathione, bilirubin, hemoglobin, citrate, lipemic material, or human serum albumin did not affect this assay system. The correlation between values obtained with our method (y) and o-cresolphthalein complexone method (CPC) (x) was: y = 1.001x + 0.077 mmol/L (r = 0.949, Sy[symbol: see text]x = 0.079, n = 100); with the other enzymatic method (x) it was: y = 0.952x + 0.021 mmol/L (r = 0.955, Sy[symbol: see text]x = 0.074, n = 100). The SEs for each method were: 0.025 mmol/L, our method; 0.023 mmol/L, CPC method; and 0.025 mmol/L, the other enzymatic method.
 ...
PMID:New enzymatic assay for calcium in serum. 869 77

We developed a new simple assay for potassium ion in serum using urea amidolyase (UAL) from yeast sp. The method is based on activation of the enzyme by potassium ion. We eliminated endogenous ammonium ion by use of glutamate dehydrogenase (GLDH), and then monitored the production of ammonium ion by UAL, urea, ATP, bicarbonate and magnesium ions. Ammonium ion was produced proportional to the potassium ion concentration and was determined by adding GLDH to produce NADP+ in the presence of 2-oxoglutarate and NADPH. We monitored the change of absorbance at 340 nm. The inhibitory effect of calcium ion to this assay was eliminated by adding glycoletherdiamine-N, N, N', N'-tetraacetic acid to the reaction. The within-assay coefficients of variation (CV) of this method were 0.9-1.55% (n = 10) at 3.32-6.18 mmol/L. Day-to-day CVs ranged from 1.49% to 2.46%. The analytical recovery was 96-108%. The correlation coefficient between the values obtained by our method (y) and those by the ion-selective electrode (ISE) method (x) was 0.994 (y = 1.032x-0.166 mmol/L, Syx = 0.110, n = 100). The presence of bilirubin, haemoglobin or other ions did not affect this assay, confirming the usefulness of this assay for clinical purposes.
 ...
PMID:New enzymatic assay with urea amidolyase for determining potassium in serum. 924 70

Helicobacter pylori is a spiral Gram-negative microaerophilic bacterium that causes one of the most common infections in humans; approximately 30-50% of individuals in Western Europe are infected and the figure is nearly 100% in the developing world. It is recognized as the major aetiological factor in chronic active type B gastritis, and gastric and duodenal ulceration and as a risk factor for gastric cancer. H. pylori normally inhabits the mucus-lined surface of the antrum of the human stomach where it induces a mild inflammation, but its presence is otherwise usually asymptomatic. A variety of virulence factors appear to play a role in pathogenesis. These include the vacuolating cytotoxin VacA, cytotoxin-associated proteins, urease and motility. All are under intense study in an attempt to understand how the bacterium colonizes and persists in the gastric mucosa, and how H. pylori infections lead to the disease state. Although an explosion of research on H. pylori has occurred within the past 15 years, most efforts have been directed at aspects of the bacterium and disease process which are of direct clinical relevance. Consequently, our knowledge of many aspects of the physiology and metabolism of H. pylori is relatively poor. This should change rapidly now that the complete genome sequence of a pathogenic strain has been determined. This review focuses attention on these more fundamental areas of Helicobacter biology. Analysis of the genome sequence and some detailed metabolic studies have revealed solute transport systems, an incomplete citric acid cycle and several incomplete biosynthetic pathways, which largely explain the complex nutritional requirements of H. pylori. The microaerophilic nature of the bacterium is of particular interest and may be due in part to the involvement of oxygen-sensitive enzymes in central metabolic pathways. However, the biochemical basis for the requirement for CO2 has not been completely explained and a major surprise is the apparent lack of anaplerotic carboxylation enzymes. Although genes for glycolytic enzymes are present, physiological studies indicate that the Entner-Doudoroff and pentose phosphate pathways are more active. The respiratory chain is remarkably simple, apparently with a single terminal oxidase and fumarate reductase as the only reductase for anaerobic respiration. NADPH appears to be the preferred electron donor in vivo, rather than NADH as in most other bacteria. H. pylori is not an acidophile, and must possess mechanisms to survive stomach acid. Many studies have been carried out on the role of the urease in acid tolerance but mechanisms to maintain the protonmotive force at low external pH values may also be important, although poorly understood at present. In terms of the regulation of gene expression, there are few regulatory and DNA binding proteins in H. pylori, especially the two-component 'sensor-regulator' systems, which indicates a minimal degree of environmentally responsive gene expression.
 ...
PMID:The physiology and metabolism of the human gastric pathogen Helicobacter pylori. 988 78

We established an enzymatic assay for measurement of serum urea nitrogen using urea amidolyase (EC 3.5.1.45) from yeast species. The method is based on hydrolysis of urea by the enzyme. In this assay, we eliminated endogenous ammonium ion by use of glutamate dehydrogenase (EC 1.4.1.4). Then in the presence of urea amido-lyase, ATP, bicarbonate, magnesium, and potassium ions, ammonium ion was produced proportionally to urea concentration in serum. The concentra-tion of ammonium ion formed was determined by adding GLDH to produce NADP(+) in the presence of 2-oxoglutarate and NADPH. We then monitored the change of absorbance at 340 nm. The inhibitory effect of calcium ion on this assay was eliminated by adding glyco-letherdiamine-N, N, N', N'-tetraacetic acid to the reaction system. The with-in-assay coefficient of variations (CVs) of the present method were 1.80-3.76% (n = 10) at 2.8-19.0 mmol/L, respectively. The day-to-day CVs were 2.23-4.59%. Analytical recovery was 92-115%. The presence of ascorbic acid, bilirubin, hemoglobin, lipemic material, ammo-nium ion, or calcium ion did not affect this assay system. The correlation be-tween values obtained with the present method (y) and those by another enzy-matic method (x) was 0.997 (y = 1.02x - 0.10 mmol/L, Sy/x = 0.841, n = 100), with a mean difference of -0.18 +/- 0.86 mmol/L [(values by reference method - that of present method) +/- SD] using the Bland-Altman technique. J. Clin. Lab. Anal. 17:52-56, 2003.
 ...
PMID:New enzymatic assay for serum urea nitrogen using urea amidolyase. 1264 Jun 27

Torulopsis glabrata is a strain of yeast that is used for the industrial production of pyruvate. Determination of the optimal nutrient environment is vital for obtaining the most efficient production system. In this study, the fermentation parameters, gene transcription levels, activities of key enzymes and metabolites levels were analyzed when either urea or ammonium chloride was used as the sole source of nitrogen. Urea caused an increase in the dry cell weight (18%) and pyruvate productivity was significantly increased (14%). The transcription levels of CAGL0M05533g (DUR1,2), CAGL0J07612g (ZWF1), and CAGL0I02200g (SOL3) were upregulated, but CAGL0G05698g (GDH2) and CAGL0L01089g (GLT1) were down-regulated. The activities of urea amidolyase, NADPH dependent glutamate dehydrogenase and glucose-6-phosphate dehydrogenase were increased by 380, 430, and 140%, respectively. The activities of arginase and glutamate synthase were decreased by 40 and 35%, respectively. The NADPH content was increased by 33%, whilst ATP content was decreased by 37%. This changed the intracellular levels of organic acids and amino acids. The results expand the understanding of the physiological characteristics of yeast species grown with different sources of nitrogen.
 ...
PMID:Urea enhances cell growth and pyruvate production in Torulopsis glabrata. 2412 77