Urease activity and

Recently, Wada et al. (1999) have demonstrated that a daily oral dose of 10 mg of bovine LF for 3-4 weeks to H. pylori-infected mice significantly decreased the number of this bacterium colonising in the stomach. The authors suggested that the glycans present in LF may bind to the bacterial adhesins, thus interfering with the attachment of H. pylori to the epithelial cells. These findings are supported by another mouse model study (Dial et al., 1998), which showed that oral administration of 4 mg of bovine LF per day for 3 weeks reduces gastric urease activity and H. pylori colonisation in the stomach. 

Olayinka, A., and Babalola, G. O. (2001). Effects of copper sulphate application on microbial numbers and respiration, nitrifier and urease activities, and nitrogen and phosphorus mineralization in an alfisol. Biol. Agric. Hortic. 19, 1-8. 

The provision of a source of nitrogen is just as important for bacterial growth as the provision of a source of energy and reference of Table 33.1 (page 478) shows that salivary urea is the most readily available source. Plaque possesses a high urease activity and a number of different... 

The pH optimum of H. pylori urease lies between pH 7.5 and 8.0, far higher than the environment often encountered by the bacteria. Therefore, surfacebound urease has a mildly alkaline pH optimum, but its activity also declines until the pH reaches 4.5, and below that, there is no detectable urease activity, and in fact, there is irreversible inactivation. Hence, unless the pH of the bacterial environment is greater than 4.0, surface urease activity will have no effect on acid survival of the organism. 

Acid activation of urea transport through the pH-gated urea channel Urel increases intrabacterial urease activity, and the ammonia produced buffers cytoplasm and periplasm. 

Moreno J.L, Garcia C., Landi L., Falchini L., Pietramellara G., Nannipieri P. The ecological dose value for assessing Cd toxicity on ATP content and DHA and urease activities of soil. Soil Biol Biochem 2001 33 483 189. 

Fig. 15.7 Activity of urease free and adsorbed on hydroxyapatite versus pH from Ref [228].

Several enzymes have been immobilized in sol-gel matrices effectively and employed in diverse applications. Urease, catalase, and adenylic acid deaminase were first encapsulated in sol-gel matrices [72], The encapsulated urease and catalase retained partial activity but adenylic acid deaminase completely lost its activity. After three decades considerable attention has been paid again towards the bioencapsulation using sol-gel glasses. Braun et al. [73] successfully encapsulated alkaline phosphatase in silica gel, which retained its activity up to 2 months (30% of initial) with improved thermal stability. Further Shtelzer et al. [58] sequestered trypsin within a binary sol-gel-derived composite using TEOS and PEG. Ellerby et al. [74] entrapped other proteins such as cytochrome c and Mb in TEOS sol-gel. Later several proteins such as Mb [8], hemoglobin (Hb) [56], cyt c [55, 75], bacteriorhodopsin (bR) [76], lactate oxidase [77], alkaline phosphatase (AP) [78], GOD [51], HRP [79], urease [80], superoxide dismutase [8], tyrosinase [81], acetylcholinesterase [82], etc. have been immobilized into different sol-gel matrices. Hitherto some reports have described the various aspects of sol-gel entrapped biomolecules such as conformation [50, 60], dynamics [12, 83], accessibility [46], reaction kinetics [50, 54], activity [7, 84], and stability [1, 80],... 

Gianfreda L, Rao MA, Violante A (1992) Adsorption, activity, and kinetic properties of urease on montmorillonite, aluminum hydroxides, and Al(OH)x-montmorillonite complexes. Soil Biol Biochem 24 51-58... 

Fig. 1. Dynamics of urease, acid phosphatase and dehydrogenase activity in soil under Cd pollution (Soil urease activity is expressed as mg NH3-N g 1 dry soil 24 h-1, Soil phosphatase activity is expressed as the mg phenol produced g-1 dry soil 24 h 1, Soil dehydrogenase activity is expressed as mgTPF g-1 dry soil 24 h 1, from Akmal et al. 2005b).

Enzyme activity (urease, amidase, dehydrogenase, pl-glucosidase, phosphatase, arylsulfatase, fluorescein diacetate hydrolysis) Laboratory incubation Indicates potential microbial activity and nutrient cycling reactions determined in nonstandard laboratory with specialized equipment highly spatially and temporally variable dependent upon organic inputs Dick et al. (1996) Parham et aL (2002)... 

PVA/acrylamide blend membranes prepared on cheese cloth support by y-irradiation induced free radical polymerization can be used for urease entrapment. The enzyme urease is entrapped in the membrane during polymerization process and using glutaraldehyde as cross-linking agent. The main advantage of this blend to this process is that it can be reused a number of times without significant loss of urease activity [292],... 

Table 6.3. Effect of nickel supplementation on hydrogenase and urease activities.

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.

Because urease activities are much greater in the soil than in the floodwater, the NH4+ is largely formed in the soil as the urea moves downward by mass flow and diffusion. The NH4+, H+ and other reactants will also move between the floodwater and soil-both upward and downward-with NH3 being lost from the floodwater by volatilization. The recovery of N in the crop therefore depends on the rate of movement of urea and its reaction products through the soil and on the rate at which the roots remove N from the downward moving pool. 

The structure of the urease active center is similar to that of adenosine deaminase, an enzyme containing one zinc(II) per active site (though see 48). This enzyme catalyzes the deamination of adenosine to inosine and NH3 (see Scheme 9), a reaction mechanistically related... 

Mustakas et al. (46) evaluated the effects of extruder-processing on nutritional quality, flavor, and stability of the product in an attempt to describe extruder conditions which would be acceptable in all three respects. Urease activity was used as an estimation of trypsin inhibitor activity thus the area between the two urease curves in Figure 2 indicates processing conditions which strike a balance between too much and too little heat treatment, showing optimal nutritional quality. Using the flavor and peroxide value isograms, processing conditions may be chosen such that acceptable flavor and stability may also be achieved. 

The title retains the trivial name for enzymes with the systematic name of urea amidohydrolase and the Enzyme Commission code number of EC 3.5.1.5. Ureases are hydrolases acting on C-N bonds (nonpeptide) in linear amides and thus belong to a group that includes glutaminase, form-amidase, and formyltetrahydrofolate deformylase. The title is plural to emphasize that urease activity may be exhibited by several protein species. Urease, singular, has come to mean by common usage, that particular enzymic protein first crystallized by Sumner from jack bean... 

It is convenient to have a method for the detection and rough estimation of urease activity in gels. A simple staining procedure using cresol red has been described (27), but a more elaborate procedure (28) employing p-nitro blue tetrazolium results in sharper definition. 

It was noted in previous reviews (1,3) that injection of urease into rabbits elicited an antibody and that the precipitate formed between urease and its antibody still possessed catalytic activity. This indicates that the antigenic and catalytic regions are not identical. A more recent study employing horse and rat antisera (66) revealed only one major antigenic component in urease preparations and confirmed the lack of complete enzyme inhibition by the precipitin reaction. 

In Azotobacter vinelandii, urease appears to be synthesized only when urea or thiourea is present (75). A study of the urease constitutive in Corynebacterium renale (76) did not reveal features remarkably different from the plant enzyme. A similar conclusion was reached in the characterization of a highly purified enzyme from B. pasteurii (77). Stewart (78) has devised a medium for the detection of urease activity in pseudomonads and has resolved uncertainties that have developed in the literature. It has been reported that Sarcina ureae produces urease as an exoenzyme (79). 

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