Multi enzyme system

Schultz AR Enzyme Kinetics From Diastase to Multi-enzyme Systems. Cambridge Univ Press, 1994. 

A. R. Schulz, Enzyme Kinetics, Erom Diastase to Multi Enzyme Systems, Cambridge University Press, New York, 1994. 

For a lucid account of the kinetics of multi-enzyme systems, the reader should consult Cornish-Bowden who defines such related parameters as flux control coefficients, summation relationships, and response coefficients. 

A liquid membrane bioreactor was developed as a means of encapsulation for a multi-enzyme system incorporating an oxidation and carbohydrate cleavage, demonstrated using a-glucosidase and glucose oxidase in the conversion of maltose to gluconic acid ... 

Multi-Enzyme Systems in Whole-Cell Biotransformations and Expression of Redox Systems 55... 

The main group of aldolases from the biocatalytic point of view is, arguably, the one that uses dihydroxyacetone phosphate (DHAP) as donor. Here, we will concentrate on that appHcations in which DHAP-dependent aldolase are part of a multi-enzyme system or, alternatively, on those in which the aldolase-catalyzed reaction is key in a multi-step synthetic pathway. 

Here, we will focus on the enzymatic routes since enzymatic preparation of DHAP is usually coupled with the aldol addition catalyzed by the aldolase representing genuine multi-enzyme systems. 

In the multi-enzyme system described by Sheldon et al. [15], the key point is the use of the phosphatase phytase from Aspergillus ficuum, which is a cheap and readily available industrial enzyme. Phytase is active at acid pH and becomes inactive at neutral pH. Thus, the pH can be used to switch on/off the activities of the various enzymes, allowing us to carry out the four-enzyme cascade in one pot. 

Scheme 4.8 Multi-enzyme system for the facile one-pot C—C bond formation catalyzed by Fuc-1 PA from readily available DHA and an aldehyde acceptor.

Scheme 4.14 L-Fructose synthesis starting from glycerol and DHAP using a multi-enzyme system with galactose oxidase, Rhal PA, catalase and APase.

Unfortunately, this multi-enzyme system cannot be performed in one pot, probably because DHAP is oxidized by galactose oxidase faster than the glycerol. In fact, the Vj jKu of the galactose oxidase for DHAP is 0.048 mM min, whereas for glycerol it is 0.38 M" min. ... 

In vitro multi-enzyme systems are set up by the combination of enzyme modules including pathway and even pathway-unrelated enzymes. Also, the synthesis of saccharides in combination with de novo enzymatic sugar synthesis can be accomplished. This so-called combinatorial biocatalysis can be performed in sequential reactors or in a one-pot reaction vessel which challenges further reaction engineering for optimization. Even the combination of an enzyme module with a chemical... 

Figure 5.1 General approach for the synthesis of glycoconjugates by multi-enzyme systems.

In the following sections we summarize multi-enzyme systems for the synthesis of glycoconjugates (Table 5.1) following the general scheme for the combination of enzyme modules (see Figure 5.1). Many of these multi-enzyme systems have been already reviewed - here we will highlight those which have been recently been developed. 

I 5 Multi-Enzyme Systems for the Synthesis of Clycoconpgates Table 5.1 Continued... 

The multi-enzyme system was recently utilized for the synthesis of dTDP-4-keto-6-deoxy-a-D-glucose 3 and dTDP-P-L-rhamnose 5 generating dlTP from dTMP by dTMP kinase and acetate kinase [66, 71]. Further combination with GerB, a dTDP-4-keto-6-deoxy-D-glucose aminotransferase, gave dTDP-4-amino-4,6-dideoxy-D-glucose [72]. 

In summary, the synthesis and in situ regeneration of nucleotide sugars by combinatorial biocatalysis suffers from the main disadvantage that each enzyme has to be produced in sufficient amounts. This affords efficient recombinant protein produchon hosts being a bottleneck for some genes [25]. However, once a multi-enzyme system has been developed, the productivity can be improved by repetitive use of the biocatalysts as demonstrated for repetitive batch syntheses with soluble enzymes [25, 38] or with immobilized enzymes [48]. The advantage... 

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