Enzymes urease

Many bacteria possess a high-affinity urea uptake system accompanied by an intracellular urease enzyme (135). Nielsen et al. (136) have measured both natural urea turnover rates and gross N mineralization rates in situ using a new... 

Enzymes are usually named in terms of the reaction that is catalyzed, commonly adding the suffix -ase to the name of the stoichiometrically converted reactant or substrate. For instance, an enzyme that catalyses the hydrolysis of urea is urease. Enzyme names can only be applied to single enzymes, especially those with termination -ase. For systems that involve the action of two or more enzymes the use of the term should be avoided and the word system should be included. 

Generally, each enzyme molecule affects different types of substances. For example, urease enzyme is only used for breaking urea into CO2 and NH. ... 

UREASE. Enzyme present in low-percentages in jackbean and soybean water soluble, its action is inhibited by heavy-metal ions. Its principal use is in the determination of urea in urine, blood, and other body fluids it splits urea into ammonia and carbon dioxide or ammonium carbonate. 

Novel microreactors with immobilized enzymes were fabricated using both silicon and polymer-based microfabrication techniques. The effectiveness of these reactors was examined along with their behavior over time. Urease enzyme was successfully incorporated into microchannels of a polymeric matrix of polydimethylsiloxane and through layer-bylayer self-assembly techniques onto silicon. The fabricated microchannels had cross-sectional dimensions ranging from tens to hundreds of micrometers in width and height. The experimental results for continuous-flow microreactors are reported for the conversion of urea to ammonia by urease enzyme. Urea conversions of >90% were observed. 

Index Entries Microscale bioreactor polydimethylsiloxane microreactor immobilized enzymes urease enzyme silicon wafer. 

Continuous studies were performed in specially prepared microreactors molded from PDMS, designated PDMS (Sylgard 184 silicone elastomer Dow Corning) poured onto silicon wafer molds. The microreactor molds were prepared using 4-in. silicon wafers of Type P, crystal orientation of , resistivity of 1 to 2 Q, and thickness of 457-575 pm from Silicon Quest (Santa Clara, C A). After preparation, mixtures of urease enzyme and PDMS (designated PDMS-E) were poured onto the microreactor mold and allowed to cure at ambient conditions. 

The combination of PDMS and urease enzyme to form a microreactor from the resulting "bioplastic" material (PDMS-E) has been reported previously (7). When enzyme concentrations were maintained at 2.5% (w/w) or less, the resulting microreactor cured with good structural integrity and high definition (e.g., well-formed microchannels and >90% retention of triangular transverse packing features in the microchannels). 

For enzyme attachment to the silicon microreactor tested, a layer-by-layer technique was employed to build a multilayer system of polyions and enzyme. Deposition of multilayers was accomplished by alternating positively and negatively charged layers of polydimethyldiallyl ammonium chloride (PDDA) and polystyrene sulfonate (PSS), respectively, to which was attached urease enzyme. After depositing in succession three layers of PDDA, PSS, and PDDA, three layers of urease enzyme were alternately deposited with three layers of PDDA. The resulting architecture is described as follows ... 

For the urease enzyme system, a reactant solution ofO.lmol/Lofurea was fed to the microreactors by Cole Parmer Series 74900 Syringe pumps. 

Urease enzyme completely converts urea into ammonium carbonate. 

Lomas, M. W. (2004b). Nitrate reductase and urease enzyme activity in the marine diatom Thalassiosira weissjlogii (BaciUariophyceae) Interactions among nitrogen substrates. Mar. Biol. 144, 37 4. 

Figure 5 Calorimetric outputs for first, -mixed- and zero-order urea/urease enzyme reactions...

Figure 6 Max rate vi. substrate concentration for the urea/urease enzyme reaction...

Enzyme Alkaline phosphatase (3-Galactosidase Peroxidase Urease Enzyme activity Enzyme activity Enzyme activity Enzyme activity... 

Figure 4 14 Potentiometric enzyme electrode for determination of biood urea, based on urease enzyme immobilized on the surface of an ammonium ion-seiective polymeric membrane electrode.

Ni Nickel None known in mammals. May be essential to plants. Found in urease enzyme MH (10-100) M... 

Urea nitrogen (BUN) B Spectrophotometry (enzymatic) Tungstic acid PFF incubate with urease enzyme at pH 6.8 to produce NH3 determine the NH3 with Nessler s reagent... 

To overcome the disparity in the optimal pH s for the isomerization and fermentation, our group [29, 35, 36] proposed a novel scheme of isomerization that incoiporates urease co-immobilized with xylose isomerase. This technique uses XI immobilized in a porous pellet for isomerization and the immobilized urease enzyme for pH control (Fig. 1). These co-immobilized enzyme pellets are dispersed in a fermentation broth, which contains urea in addition to the other necessary ingredients for fermentation. Theoretically, it is possible to sustain a significant pH gradient between the bulk liquid and the core region of the pellet... 

The concentration of urea in blood (blood urea nitrogen, BUN) is an important parameter in clinical chemistry for assessing kidney failure. Since urease enzyme sensors rely mainly on indication of the pH change during urea hydrolysis, problems in their application to body fluids are connected with the susceptibility of the sensors to disturbances by sample pH and buffer capacity. 

FIGURE 8 Confocal fluorescence microscopy images of (PSS/EAH) PSS capsules loaded with SNARF-1 dextran (MW = 70kDa) and urease enzyme in water (image A) and 0.1 M urea concentrations (image B). The Table 1 shows the increase of mean energy of individual capsules before (Fj ) and after the addition 0.1 M urea solution to water capsule suspension. The red fluorescence emission was accumulated at 600-680 run after excitation by the FITC-TRIC-TRANS laser at 543 nm. 

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