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)

By counting the volatile molecules produced by an immobilized-enzyme catalyzed reaction which is interfaced to a mass spectrometer via a semi-permeable membrane, a general approach to biochemical measurement and detection is obtained which offers the potential of high sensitivity, specificity and speed. In combination with molecule microscopy, this method should allow, for example, a mapping of suitable enzyme distributions in non-stained and non-fixed tissue slices. Immobilized urease (urea amidohyrdrolase, EC 3.5.1.5) was used to assay urea using CO2 as the volatile product, and alcohol dehydrogenase (alcohol:NAD+ oxidoreductase, EC 1.1.1.1) was used to assay NADH using ethanol as the volatile product.
 ...
PMID:Biochemical assay by immobilized enzymes and a mass spectrometer. 18 Oct 86

A direct enzymatic micromethod (sample volume, 3mul) has been adapted to the centrifugal analyzer (ENI-GEMSAEC) for measurement of urea in plasma and urine. The method is based on urease (urea amidohydrolase, EC3.5.1.5)/glutamate dehydrogenase [l-glutamate:NAD(P)+oxidoreductase (deaminating), EC1.41.3] coupled reactions, and uses a two-point fixed-time (t(1)=20s,t(2)=50s)kinetic scheme for monitoring the rate of comsumption of NADH at 340 nm. Sensitivity and precision of the method are excellent,and results compare well with those from a commonly used continuous-flow method.
 ...
PMID:Direct enzymatic determination of urea in plasma and urine with a centrifugal analyzer. 97 5

An enzymatic, fluorometric method is described for determination of serum urea on silicone-rubber pads. In this method, the reagents are lyophilized on the surface of the pads, NADH on one side and a mixture of urease, glutamate dehydrogenase, and alpha-ketoglutarate on the other. The rate of disappearance of NADH fluorescence at 460nm (excitation wavelength, 340 nm) is monitored and related to serum urea concentration. The calibration curve is linear to 250 mg of urea per liter. The method affords a rapid, simple, and inexpensive means for urea assay, the results of which correlate well with automatic diacetyl monoxime method (correlation coefficient, 0.998).
 ...
PMID:Enzymatic determination of serum urea on the surface of silicone-rubber pads. 111 80

1. Isolated hepatocytes were used to establish the reasons for the accumulation of aspartate, previously observed when the isolated rat liver was perfused with ethanol in the presence of alanine or ammonium lactate. 2. The isolated cells did not form aspartate when incubated with alanine and ethanol, but much aspartate was formed on incubation with ammonium lactate and ethanol. 3. Urea was the main nitrogenous product on incubation with alanine, in contrast with the perfused liver, where major quantities of NH4+ are also formed. When the formation of urea was nullified by the addition of urease, alanine plus ethanol caused aspartate formation, indicating that aspartate formation depends on the presence of critical concentrations of NH4+. 4. The accumulated aspartate was present in the cytosol. Ethanol halved the content of 2-oxoglutarate in the cytosol and more than trebled that of glutamate in the mitochondria. 5. The findings support the assumption that 2-oxoglutarate formed by the mitochondrial aspartate aminotransferase is not translocated to the cytosol in the presence of ethanol and NH4+, because it is rapidly converted into glutamate, the dehydrogenation of ethanol providing the required NADH. Aspartate, however, is translocated to the cytosol and accumulates there because of the lack of stoicheiometric amounts of oxoglutarate.
 ...
PMID:The accumulation of aspartate in the presence of ethanol in rat liver. 120 Oct 7

A modified end-point enzymatic method for the measurement of ammonia in stool water is presented. A protein precipitation step was included in order to inactivate urease and faecal enzymes, which oxidise NADH. The modified method is reliable, with acceptable precision and accuracy, and is linear up to a concentration of 1.5 mmol/l.
 ...
PMID:Measurement of faecal ammonia. 148 77

In order to provide a basis for obtaining further information concerning the host response to Helicobacter pylori urease, four assay methods for detecting urease-inhibiting activity in serum were examined. A quantitative assay, established in a COBAS BIO centrifugal fast analyzer and based on detection of the consumption of NADH by glutamate dehydrogenase stimulated by ammonia production, was considered most suitable for large-scale serological work. Serum samples from 63 children (aged 5 to 16 years), 28 of whom had seropositive H. pylori gastritis, were assayed. One of the serum samples in this latter group showed significant inhibitory activity. This serum sample was one of 13 in the seropositive group known to bind to urease antigen. It showed no inhibitory activity against Bacillus pasteurii or jack bean urease. Protein A binding and heat treatment indicated that the inhibitory activity was immunoglobulin G mediated. The patient from whom this sample was collected showed no distinctive features in his illness. The COBAS BIO analyzer-based urease inhibition assay provides a new tool for studying one aspect of the host response to H. pylori infection.
 ...
PMID:Assay of urease-inhibiting activity in serum from children infected with Helicobacter pylori. 158 44

A multienzyme system consisting of leucine dehydrogenase (EC 1.4.1.9), L-lactic dehydrogenase (EC 1.1.1.27), urease (EC 3.5.1.5), and dextran-NAD+ was microencapsulated within artificial cells. This system could convert ammonia and urea into essential amino acids, L-leucine, L-valine, and L-isoleucine. L-lactate acted as a cosubstrate for the regeneration of dextran-NADH. Greater concentrations of L-lactate favored the higher conversion ratios. The effects of ammonium salts and urea on reaction rate were also studied. The relative reaction rates in ammonium salts solutions were 44.6-78.8% of those in urea solutions. More than 90% of the original activity was retained when artificial cells were kept at 4 degrees C for 6 wk.
 ...
PMID:Conversion of ammonia or urea into essential amino acids, L-leucine, L-valine, and L-isoleucine using artificial cells containing an immobilized multienzyme system and dextran-NAD. L-lactic dehydrogenase for coenzyme recycling. 170 78

Artificial cells containing glucose dehydrogenase (EC 1.1.1.47), leucine dehydrogenase (EC 1.4.1.9), urease (EC 3.5.1.5), and dextran-NAD+ were prepared. Ammonia or urea could be converted into L-leucine, L-valine, and L-isoleucine with artificial cells. Low-specific-activity glucose dehydrogenase could effectively regenerate dextran-NADH, which was recycled at a rate of 0.4 to 0.5 cycle per minute under reaction conditions. The effects of ammonium salts and urea on the conversion rate for the leucine dehydrogenase multienzyme system were also studied. The relative activities in ammonium salts solutions were 40 to 70% of those in urea solutions.
 ...
PMID:Conversion of ammonia or urea into L-leucine, L-valine, and L-isoleucine using artificial cells containing an immobilized multienzyme system and dextran-NAD+. Glucose dehydrogenase for co-factor recycling. 245 27

A rapid enzymatic assay method for ammonia was developed by using glutamine synthetase from glutamate-producing bacteria together with pyruvate kinase, lactate dehydrogenase, and NADH. The time required for determination of 25 nmol of ammonia was 5 min with 1 unit of glutamine synthetase, as opposed to 14-30 min with 1 unit of glutamate dehydrogenases from various sources. The present method was used to determine ammonia in serum, microbiol-culture broth, and waste water. The method can be modified for spectrophotometry in the visible region by substituting pyruvate oxidase, peroxidase, and appropriate chromogens for lactate dehydrogenase and NADH. With 4-aminoantipyrine (4AA) and phenol, and with 4AA and N-ethyl-N-2-hydroxyethyl-m-toluidine as chromogens, the sensitivity of ammonia determination was 0.65 and 1.7 times that with glutamate dehydrogenase, respectively. The present method was also applicable to the continuous detection of the activity of some ammonia-forming enzymes such as guanase, adenosine deaminase, and urease and to the determination of 0.5-30 microM ATP-ADP after some modification of the mixture.
 ...
PMID:A rapid assay method for ammonia using glutamine synthetase from glutamate-producing bacteria. 288 29

After a brief review of the methods for determination of urea by continuous flow analyzers, a method is described based on the urease splitting of urea followed by NH3 reaction with alfa-ketoglutarate + NADH2 catalysed by GLDH. The method has been applied to continuous flow analyzers and seems to be promising.
 ...
PMID:[Review of the methods of determination of blood urea with continuous-flow analyzers and a proposal of a completely enzymatic UV method for urea by a continuous-flow analyzer]. 718 46


1 2 3 Next >>