“…Enzyme concentration is expressed as the molarity of glucose-reducible E-FAD. The value of Ae450 for oxidized -minus -reduced enzyme was taken to be 13.1 mm-' -cm-' (Duke et al 1969) and the procedure for determining the concentration of soluble glucose oxidase has been described (Weibel & Bright, 1971).…”
Section: Methodsmentioning
confidence: 99%
“…Because of these factors, we considered it worthwhile to study in insolubilized form an enzyme which is well characterized mechanistically in homogenous solution, and for which an optical determination of bound active enzyme could be devised. (1) The kinetic mechanism of the glucose oxidase reaction has been thoroughly studied by a combination of rapid-reaction and conventional techniques (Gibson, Swoboda & Massey, 1964;Bright & Gibson, 1967;Nakamura & Ogura, 1967;Duke, Weibel, Page, Bulgrin & Luthy, 1969;Bright & Appleby, 1969;Weibel & Bright, 1971) and the important kinetic steps contributing to turnover with glucose as a substrate at pH 5.5 and 250C are given in eqns.…”
1. The spectrophotometric and steady-state kinetic properties of glucose oxidase (EC 1.1.3.4, from Aspergillus niger) that is covalently linked to porous glass beads have been examined. These properties have been compared with those of soluble glucose oxidase, for which the kinetic mechanism at pH5.5 and 25 degrees C has been established previously by a combination of conventional and rapid-reaction techniques to be the following: [Formula: see text] where E(o) and E(r) represent oxidized and reduced forms of the enzyme, respectively. 2. The ratio k(+4)/k(+2) is unchanged after insolubilization, and evidence is presented which suggests that the absolute magnitudes of k(+4) and k(+2) are unchanged. 3. The kinetic efficiency of the insolubilized enzyme is greatly enhanced because of a 14-fold increase in the apparent affinity of glucose for E(o). This effect is attributed either to the binding of glucose to the glass surface or to a change in enzyme structure imposed by the insolubilization process. 4. Only 6% of the insolubilized enzyme which can be reduced by glucose is catalytically active. It is shown by calculation and direct experimental evidence that this fraction of catalytically active enzyme is bound to the exterior bead surface. The remaining 94% of the enzyme is bound within the pore network and may be subject to severe substrate diffusion control.
“…Enzyme concentration is expressed as the molarity of glucose-reducible E-FAD. The value of Ae450 for oxidized -minus -reduced enzyme was taken to be 13.1 mm-' -cm-' (Duke et al 1969) and the procedure for determining the concentration of soluble glucose oxidase has been described (Weibel & Bright, 1971).…”
Section: Methodsmentioning
confidence: 99%
“…Because of these factors, we considered it worthwhile to study in insolubilized form an enzyme which is well characterized mechanistically in homogenous solution, and for which an optical determination of bound active enzyme could be devised. (1) The kinetic mechanism of the glucose oxidase reaction has been thoroughly studied by a combination of rapid-reaction and conventional techniques (Gibson, Swoboda & Massey, 1964;Bright & Gibson, 1967;Nakamura & Ogura, 1967;Duke, Weibel, Page, Bulgrin & Luthy, 1969;Bright & Appleby, 1969;Weibel & Bright, 1971) and the important kinetic steps contributing to turnover with glucose as a substrate at pH 5.5 and 250C are given in eqns.…”
1. The spectrophotometric and steady-state kinetic properties of glucose oxidase (EC 1.1.3.4, from Aspergillus niger) that is covalently linked to porous glass beads have been examined. These properties have been compared with those of soluble glucose oxidase, for which the kinetic mechanism at pH5.5 and 25 degrees C has been established previously by a combination of conventional and rapid-reaction techniques to be the following: [Formula: see text] where E(o) and E(r) represent oxidized and reduced forms of the enzyme, respectively. 2. The ratio k(+4)/k(+2) is unchanged after insolubilization, and evidence is presented which suggests that the absolute magnitudes of k(+4) and k(+2) are unchanged. 3. The kinetic efficiency of the insolubilized enzyme is greatly enhanced because of a 14-fold increase in the apparent affinity of glucose for E(o). This effect is attributed either to the binding of glucose to the glass surface or to a change in enzyme structure imposed by the insolubilization process. 4. Only 6% of the insolubilized enzyme which can be reduced by glucose is catalytically active. It is shown by calculation and direct experimental evidence that this fraction of catalytically active enzyme is bound to the exterior bead surface. The remaining 94% of the enzyme is bound within the pore network and may be subject to severe substrate diffusion control.
“…By synthesizing H 2 O 2 in the pores of the top membrane, we are able to regulate its generation, thus eliminating unnecessary waste. In order to achieve this, the pores of the top membrane were functionalized using a versatile polycation/polyanion layerby-layer (LbL) assembly technique (18)(19)(20)(21) for the immobilization of negatively charged glucose oxidase (GOx), which converts glucose and oxygen to H 2 O 2 and gluconic acid (22) (Fig. 1B).…”
Many current treatments for the reclamation of contaminated water sources are chemical-intensive, energy-intensive, and/or require posttreatment due to unwanted by-product formation. We demonstrate that through the integration of nanostructured materials, enzymatic catalysis, and iron-catalyzed free radical reactions within pore-functionalized synthetic membrane platforms, we are able to conduct environmentally important oxidative reactions for toxic organic degradation and detoxification from water without the addition of expensive or harmful chemicals. In contrast to conventional, passive membrane technologies, our approach utilizes two independently controlled, nanostructured membranes in a stacked configuration for the generation of the necessary oxidants. These include biocatalytic and organic/inorganic (polymer/ iron) nanocomposite membranes. The bioactive (top) membrane contains an electrostatically immobilized enzyme for the catalytic production of one of the main reactants, hydrogen peroxide (H 2 O 2 ), from glucose. The bottom membrane contains either immobilized iron ions or ferrihydrite/iron oxide nanoparticles for the decomposition of hydrogen peroxide to form powerful free radical oxidants. By permeating (at low pressure) a solution containing a model organic contaminant, such as trichlorophenol, with glucose in oxygen-saturated water through the membrane stack, significant contaminant degradation was realized. To illustrate the effectiveness of this membrane platform in real-world applications, membrane-immobilized ferrihydrite/iron oxide nanoparticles were reacted with hydrogen peroxide to form free radicals for the degradation of a chlorinated organic contaminant in actual groundwater. Although we establish the development of these nanostructured materials for environmental applications, the practical and methodological advances demonstrated here permit the extension of their use to applications including disinfection and/or virus inactivation.enzyme catalysis | functionalized membranes | pollutant | microfiltration | responsive materials
SummaryThe overall rate of reaction of buffered gel-immobilized glucose oxidase particles is described by means of an enzyme rate equation which relates the overall reaction rate of a particle to the free solution characteristics of the enzyme, the effective diffusivity of the limiting substrate in the gel, the characteristic particle size, and the limiting substrate concentration adjacent to the gel surface. This equation accounts quantitatively for the limitation of the overall rate of reaction by substrate diffusion, and it is used to illustrate the influence of the system parameters, i.e., particle size, enzyme concentration, and pH, on the extent of the diffusional resistance associated with gel-immobilized glucose oxidase particles.The enzyme rate equation is generally applicable to those enzymes whose kinetics approximately follow Michaelii-Menten form when in free solution.
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