Multiple enzyme and substrate systems

In the preceding section, we discussed how the addition of a second substrate. I. to enzyme-catalyzed reactions could deactivate the enzyme and greatly inhibit the reaction. In the present section, we look not only at systems in which the addition of a second substrate is necessary to activate the enzyme, but also at other multiple-enzyme and multiple-substrate systems in which cyclic regeneration of the activated enzyme occurs. Cell growth on multiple substrates is given in the Sunman, Vmes. 

Enzyme Regeneration. The first example considered is the oxidation of glucose (Sf) with the aid of the enzyme glucose oxidase (repre,seiiied as either G.O. or ( ]) to give 5-gluconolactone (P)  

In this reaction, the reduced form of glucose oxidase (G.O.H2), which will be represented by E, cannot catalyze further reactions until it is oxidized back to E . This oxidation is usually carried out by adding molecular oxygen to the system so that glucose oxidase, E, . is regenerated. Hydrogen peroxide is also produced in this oxidation regeneration step  

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Inhibition of Enzyme Reactions 391 Multiple Enzyme and Substrate Systems 392... 

Our discussion of enzyme.s is continued in the Professional Reference Shelf on the DVD-ROM and on the Web where we describe multiple enzyme and. substrate systems, enzyme regeneration, and enzyme co-tactors (see R9.6). 

Miniaturized proteomic analysis devices include enzyme assays and immunoassays. The enzyme assay chip is mainly a sophisticated incubator and flowthrough system. It can perform multiple functions typically required by the biochemist, namely, diluting substrate and buffer, mixing enzyme and substrate, incubating during conversion, and allowing for detection in a flow channel. Immunoassay chips are similar... 

Although there is no disagreement concerning the appearance of the endoplasmic reticulum on thin section, the tridimensional reconstruction of this planar structure is debated. The controversy is easier to understand if the proposed roles of the endoplasmic reticulum in biology are kept in mind. Among these hypothetical roles are (1) the endoplasmic reticulum provides compartments within the cytoplasm (2) it separates multiple-enzyme systems or separates the enzyme from its substrate (3) it provides a support for enzymes and substrates, thereby facilitating reaction and (4) it furnishes an intracellular circulatory system in connection with the exterior, which promotes rapid diffu-... 

The plug flow reactor has been mainly utilized for the removal of phenol in waste streams by HRP [76, 83] and Coprinus cinereus peroxidase [2]. According to Buchanan et al. [83], who modeled the kinetics of the HRP-aromatic substrate system and applied to PFR and CSTR, plug-flow configuration is recommended when working with low HRT, since considerably less enzyme would be required for equal phenol removal. However, for long HRTs, a multiple-stage CSTR would be more efficient than a PFR, due to the lower rate of enzyme inactivation. 

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