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 screen-printed three-electrode amperometric biosensor based on urease and the nicotinamide adenine dinucleotide hydrogen (NADH)-glutamic dehydrogenase system was developed and applied to the screening of heavy metals in environmental samples. The development of an amperometric sensor for the monitoring of urease activity was feasible by coupling the urea breakdown reaction catalysed by urease to the reductive ammination of ketoglutarate catalysed by glutamic dehydrogenase (GLDH). The ammonia provided by the urea conversion is required for the conversion of ketoglutarate to glutamate with the concomitant oxidation of the NADH cofactor. NADH oxidation is monitored amperometrically at 0.3 V (vs. Ag/AgCl) after urease immobilization onto the screen-printed three-electrode configuration. Immobilization of urease on the surface of screen-printed electrodes was performed by entrapment in alginate gel and adsorption on the electrode in a nafion film. Low sensitivity to inactivation by metals was recorded after urease entrapment in alginate gel with detection limits of 2.9 and 29.8 mg L(-1) for Hg(II) and Cu(II), respectively. The use of the negatively charged nafion film created a more concentrated environment of cations in proximity to the enzyme, thus enhancing the urease inhibition when compared to gel entrapment. The calculated detection limits were 63.6 and 55.3 microg L(-1) for Hg(II) and Cu(II), respectively, and 4.3 mg L(-1) for Cd(II). A significant urease inactivation was recorded in the presence of trace amounts of metals (microg L(-1)) when the enzyme was used free in solution. Analysis of water and soil samples with the developed nafion-based sensor produced inhibition on urease activity according to their metal contents. The obtained results were in agreement with the standard methods employed for sample analysis. Nevertheless, the use of the amperometric assay (with free urease) proved more feasible for the screening of trace amounts of metals in polluted samples.
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PMID:Urease-glutamic dehydrogenase biosensor for screening heavy metals in water and soil samples. 1530 Mar 52

Urea could be effectively converted into L-glutamic acid with semipermeable nylon-polyethylenimine artificial cells containing L-glutamic dehydrogenase (EC 1.4.1. 3), yeast alcohol dehydrogenase (EC 1.1.1.1), urease (EC 3.5.1. 5) and soluble dextran-NAD(+). For batch conversion, the artificial cell suspension to total reaction volume ratios ranged from 1 in 5 to 1 in 60. From 22.6 to 53.4 micromol of L-glutamic acid could be produced by 0.4 mL artificial cell suspension within 2 h. The corresponding conversion ratios were 56.5-11. 1%. The L-glutamic dehydrogenase multienzyme system showed a good storage stability: 66.0% of the original activity was retained after 1 month of storage at 4 degrees C. A small bioreactor was prepared to contain 4.0 mL artificial cells. At a flow rate of SV = 1.5 h(-1), the maximum conversion rate was 49.6 micromol L-glutamic acid/p h. Thirty-eight percent of the maximum activity was retained when continuously used for four days at 22 degrees C. A kinetic analysis for the L-glutamic dehydrogenase multienzyme system was studied. The Michaelis constants are as follows: alpha-ketoglutarate is 0.838 mM; urea is 1.90 mM; dextran- NAD(+) is 0.345 mM; and ethanol is 5.31 mM.
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PMID:Conversion of alpha-ketoglutarate into L-glutamic acid with urea as ammonium source using multienzyme systems and dextran-NAD+ immobilized by microencapsulation within artificial cells in a bioreactor. 1858 59

The aim of the study was to investigate protein intake in groups of different physical activity. The research was undertaken over a group of young people of different physical activity (age group 15-18 years) including ballet dancers, karate fighters, cross runners as well as adolescents of average physical activity (female and male). The investigation was performed in two series. The first--before intense exercise training and the second--after intense exercise training. In control group there was only one series. Urea was estimated by using urease which converts urea into ammonia, CO2 and glutamic dehydrogenase reaction via measurements of ammonia derived from urea. The amounts of urea were applied for counting quantity of consumed proteins. In the physically active groups the protein intake was too low in comparison to required.
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PMID:[Protein intake in selected youth groups of different physical activity and requirements for athletes]. 1909 82

Enzymic activities have been measured in cell-free extracts from nitrogen-starved cultures ofAnkistrodesmus braunii. During ten hours of nitrogenstarvation the activities of the enzymes nitrite reductase (E.C.1.6.6.4), glutamic dehydrogenase (E.C.1.4.1.4), glutamine synthetase (E.C.6.3.1.2) and urea amidolyase (E.C.3.5.1.5) were derepressed while the activities of the enzymes malate dehydrogenase (E.C.1.1.1.37) and hexokinase (E.C.2.7.1.1) remained more or less unchanged. In contrast, the photosynthetic capacity of the nitrogen-starved cultures declined rapidly and accompanying this decline were losses in the activities of ribulose diphosphate carboxylase (E.C.4.1.1.39) and triose phosphate-NADP-dehydrogenase (E.C.1.2.1.13).
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PMID:Some effects of nitrogen-starvation on nitrogen and carbohydrate metabolism inAnkistrodesmus braunii. 2442 51