Urease Subject

Figure 6.5. Immunoblot of the urease large subunit. Extracts of H. pylori wild type (WT) and a hypA mutant from cells grown without nickel supplementation were subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and identified by blotting with an anti-urease large-subunit antiserum. Urease activity was 58pmolmin mg for the wild type and Opmolmin" mg for the hypA mutant.

Figure 2 Mechanism of urease. This proposed mechanism features binding of urea through its carbonyl group to one of the Ni ions, making the carbon subject to nucleophilic attack by the bridging hydroxide leading to liberation of NH2, which is protonated by to form ammonia,...

The maximal intestinal immunization can be achieved by intra-Peyer s patch immunization, and thus this method can be used to screen oral vaccine candidate antigens without the added complication of simultaneously testing oral-delivery systems. Immunization of subjects against Helicobacter pylori by intra-Peyer s patch resulted in an 84-91% reduction in H. pylori infection compared with unimmrmized controls. The therapeutic efficacy of the recombinant H. pylori urease vaccine in mice was shown to be comparable with that achieved with the combined anti-biotic/antacid treatment in humans. The oral vaccination is preferred to conventional treatment of ulcers because it is a very simple and quick procedure compared with long-term conventional treatment. In addition, vaccines use the defense mechanisms of the body to establish long-lasting immunity. ... 

Yeast invertase,30 32 33 acid phosphatase,29 32 35 37 39 urease,29 /3-glucosi-dase,29 dCMP-amino hydrolase31 and malic enzyme34 36 have been immobilized in gel form on both flat and capillary membranes. Cellulosic and polyamide polymers have been used as supporting membrane matrices. In all instances, immobilized enzymes behave in a manner almost identical to their behavior in homogenous solution, independent of the nature of the polymer. Neither allosteric nor pseudo-allosteric enzymes, proteins whose kinetic behavior is affected by the presence of particular compounds in the reaction environment (ligands), show different kinetic behavior, as they do when subjected to less gentle immobilization procedures.31 34 36... 

Figure 2 Mechanism of urease. This proposed mechanism features binding of urea through its carbonyl group to one of the Ni ions, making the carbon subject to nucleophilic attack by the bridging hydroxide leading to liberation of NH2, which is protonated by to form ammonia, and carbamate, which hydrolyzes to another mole of ammonia and carbonic acid. The same mechanism with proton transfer from water (instead of histidine) to ammonia is another possibility. Another possibility would be urea binding in a monodentate manner with a terminal hydroxide on Ni2 as the nucleophile...

Canavalia urease has been the subject of extensive physical and chemical investigation because of its availability in pure form (see Reithel, 1971 Bailey and Boulter, 1971). Sedimentation velocity investigations reveal six... 

The determination of pesticides has become increasingly important in recent years because of the widespread use of these compounds, which is due to their large range of biological activity and a relatively low persistence. The development of biosensors for pesticides is the subject of considerable interest, particularly in the areas of food and environmental monitoring. Several enzymes such as cholinesterase enzymes (AChE, BChE) and urease have been used in the design of direct electrochemical biosensors for the detection of pesticides (Larsen et al., 2007). Analytical devices based on the inhibition of cholinesterase have been widely used for the detection of organic phosphate compounds and carbamate pesticides. 

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