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

A simple device, consisting of a heat sensor placed in close contact to fibres containing enzymes and connected to a temperature measuring unit has been developed. The system monitors the temperature variations due to the enzymatic reaction when substrate solutions flow through the measuring cell. Fibres containing the enzymes glucose oxidase and catalase for the determination of glucose and fibres containing urease for the determination of urea were tested. A linear relationship between the substrate concentration and the deltaT recorded was obtained in both cases.
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PMID:Monitoring of metabolites applying fibre-entrapped enzymes in a calorimetric system. I -- Glucose and urea determination. 46 7

We describe the use of immobilized enzymes in assay methods for the determination of glucose with glucose oxidase, uric acid with uricase, and urea with urease in serum samples. The enzyme reactor tubes were adapted to continuous-flow analyzers (Technicon AA II, SMA 12/60, and SMAC) used in routine laboratory determinations, and results with their use were compared to those from assays involving soluble enzymes. We substituted the reactors for the free enzyme reagents in the respective channels of the SMA 12/60 and SMAC, without modifying the parameters of the remaining channels. We compared assay sensitivity, precision, and carryover for immobilized and conventional liquid enzymes. Immobilized enzyme reactors provide accurate, reliable, convenient, and economical alternatives to the use of free enzyme reagents in these systems.
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PMID:The use of immobilized enzyme reactors in continuous-flow analyzers for the determination of glucose, urea, and uric acid. 47 24

Glucose oxidase, uricase, and urease were immobilized on the interior surface of activated polyamide tubing. The shelf-life of such enzyme bearing tubes was at least six months. The tubes were used for continuous-flow analysis of glucose, uric acid, and urea with conventional systems and with hybrid micro-scale systems in which modules of different manufacture were combined. The length of enzyme-bearing tube required for each system was ascertained empirically. Each tube could be used for several thousand assays, but glucose oxidase-bearing tubes were more stable than urease- or uricase-bearing tubes. Results for patients' samples correlated well with results obtained by accepted methods.
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PMID:Immobilized enzymes in continuous-flow analysis. 76 73

A device, the enzyme thermistor, is described which is capable of measuring changes in heat due to enzymic reactions. The sensor, a thermistor, is in direct contact with the site of reaction through its placement in a microcolumn filled with an immobilised enzyme preparation. The substrate solution flows past the thermistor tip, and as much as approx. one half of the total heat evolved can be registered as temperature change, deltat. Glass-bound glucose oxidase (EC 1.1.3.4), penicillinase (EC 3.5.2.6), trypsin (EC 3.4.21.4) and urease (EC 3.5.1.5) were used for the determination of glucose, penicillin G, benzoyl-L-arginine ethyl ester and urea respectively. Linear relationships between the deltat recorded and the concentration of substrate were obtained in all cases.
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PMID:Determination of heat changes in the proximity of immobilised enzymes with an enzyme thermistor and its use for the assay of metabolites. 117 49

Single and multisensor field effect transistors (FET) with a pH-sensitive Si/SiO2/Si3N4/Ta2O5-gate and reference electrode (for single sensor) were developed and used for manufacturing the following biological (Bio)-FETs: for glucose analysis, glucose oxidase-FET (GOD-FET); for urea analysis, urease-FET; and for cephalosporin C analysis, cephalosporinase-FET. The GOD-FETs were integrated into flow injection analysis (FIA) of the Eppendorf variables analyser (EVA) system and used for monitoring the glucose concentration in microbial cultivation and production processes with recombinant Escherichia coli K12 MF, recombinant E. coli JM103, Saccharomyces cerevisiae H620, and Candida boidinii. Urease-FET-FIA was used to monitor the urea concentration in a simulated cultivation of Cephalosporium acremonium and urease-FET-FIA and GOD-FET-FIA for the monitoring of urea and glucose concentrations in simulated S. cerevisiae cultivations.
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PMID:Monitoring and control of biotechnological production processes by Bio-FET-FIA-sensors. 136 6

1. Glucose oxidase (EC 1.1.3.4) and urease (EC 3.5.1.5) were covalently attached through glutaraldehyde to low-molecular-weight nylon powder. 2. Immobilized derivatives of glucose oxidase and urease were prepared by cross-linking the respective enzymes within the matrix of a nylon membrane. 3. An improved process is described for the immobilization of glucose oxidase and urease on the inside surface of partially hydrolysed nylon tube. 4. Automated analytical procedures are described for the determination of glucose with each of the three immobilized glucose oxidase derivatives and for the determination of urea with each of the three immobilized urease derivatives. 5. The efficiencies of the three immobilized enzyme structures as reagents for the automated determination of their substrates were compared.
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PMID:The immobilization of enzymes on nylon structures and their use in automated analysis. 464 9

Simple solid-phase optoelectronic sensors for penicillin, urea, and glucose are described. Triphenylmethane dyes such as bromcresol green and bromthymol blue were derivatized with glutathione and co-immobilized with appropriate enzymes to a transparent membrane sandwiched between a red-light-emitting diode and a silicon photodiode with integral amplifier. In the presence of the corresponding substrates, catalytic action in the enzyme-dye membrane perturbs the local pH and causes characteristic color changes in the membrane which are monitored as a rise or fall in the output voltage of the detector system. With enzymes such as penicillinase, urease, and glucose oxidase, the response of the optoelectronic sensors is extremely reproducible over the concentration range 0-10 mM penicillin G, urea, or D-glucose, respectively. This report describes the construction and operation of these simple, inexpensive, and reagentless optoelectronic sensors.
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PMID:Solid-phase optoelectronic sensors for biochemical analysis. 674 21

Serum from patients was pooled, filtered, dispensed, and frozen. This pooled specimen was used for accuracy control in 64 participating laboratories in Sweden. Mean values ("state-of-the-art" values) were obtained for creatinine, cholesterol, glucose, urea, uric acid, and cortisol. These values were compared with values obtained with highly accurate reference methods based on isotope dilution-mass spectrometry. Differences were marked in the case of determination of creatinine and cortisol. Concerning the other components, the differences between the state-of-the-art value and the values obtained with the reference methods were negligible. Moreover, the glucose oxidase and the oxime methods for determination of glucose and urea were found to give significantly lower values than the hexokinase and urease methods, respectively. We conclude that methods with a higher degree of accuracy are required for routine determination of creatinine and cortisol.
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PMID:Accuracy of some routine method used in clinical chemistry as judged by isotope dilution-mass spectrometry. 701 32

The characteristics of the developed conductometric biosensors for urea and glucose determination are described. Conductometric transducers based on thin-film interdigitated metal (Au, Cr, Cu, Ni) electrodes were studied, and enzymes urease and glucose oxidase were used for the selective membranes formation on the chips having gold electrodes. The influence of ionic strength and buffer capacity of the samples on the biosensors response in kinetic and steady-state modes of measurements was thoroughly tested. It was shown that the kinetic response of the sensors does not depend on the buffer capacity of the analyzed sample. In basic features the performance of the developed biosensors is rather close to that of respective enzyme field effect transistor, though the former are much superior when the technological complexity of the transducer itself is considered and taking into account that conductometric sensors require no reference electrode.
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PMID:Thin-film conductometric biosensors for glucose and urea determination. 806 May 91

An alternative method based on thin-film conductometric microsensor is suggested for studying enzyme kinetics. It is established that the immobilized enzyme as well as soluble one is described by the classic lows of enzyme kinetics. Major parameters (Km and Vmax) are identical to those measured by the widely used methods and their amounts are 1.33 mM and 9.04 microS/min for soluble urease and 3.73 mM and 13.8 microS/min for immobilized urease; 5.26 mM and 13.9 microS/min for immobilized glucose oxidase; 13.6 mM and 122.0 microS/min for immobilized acetyl cholinesterase; 10.8 mM and 129.9 microS/min for immobilized butyryl cholinesterase. The possibility of conductometric analyzer application for detection of toxin concentration, in particular pesticides, is shown. Advantages and disadvantages of the system suggested are discussed.
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PMID:[Use of conductometric microsensors for studying kinetic parameters of enzymes]. 816 Feb 98


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