Enzymes PEG-modified

Surface-Modified Enzymes. Enzymes acting in nearly anhydrous organic solvents always give rise to heterogeneous systems (Sect. 3.1). In order to turn them into homogeneous systems, which can be controlled more easily, proteins can be modified in order to make them soluble in lipophilic organic solvents. This can be readily achieved by covalent attachment of the amphipathic polymer polyethylene glycol (PEG) onto the surface of enzymes [460]. The pros and cons of PEG-modified enzymes are as follows [461, 462] ... 

The cyanuric chloride/PEG method seems to work for all classes of enzymes, including hydrolases (lipases [469], proteases, glucosidases [470]) and redox enzymes (dehydrogenases, oxidases [471]). The residual activities are usually high (50-80%), and for most enzymes about five to ten PEG chains per enzyme molecule are sufficient to render them soluble in organic solvents. Care has to be taken to avoid extensive modification which leads to deactivation. PEG-modified enzymes may be recovered from a toluene solution by precipitation upon the addition of a hydrocarbon such as petroleum ether or hexane [472]. 

The modification of enzyme by attaching ions or molecules is a suitable way for providing it with useful fimctions. For example, the use of modifiers such as polyethylene glycol (PEG) (7,2) and synthetic lipids (i) enhances the affinity for hydrophobic environments. PEG-modified enzymes are soluble and active in various organic solvents as well as aqueous solutions (7,2). Lipid-modified enzymes are insoluble in aqueous solutions, but show catal c activities in both aqueous and organic media (i). These unique properties lead us to apply PEG- and lipid-modified enzymes in the construction of enzyme electrodes. 

Glucose-Sensing Electrode based on PEG-Modified Enzyme... 

PEG-modified enzymes prepared by coupling proteins with PEG in aqueous buffer solution are soluble not only in aqueous solution but in hydrophobic environments. Table 2 summarizes the list of PEG-enzymes prepared by the authors for the application to biotechnological processes. 

Generally, native enzymes never dissolve in organic solvents. We have reported that PEG-modified enzymes dissolved not only in various organic solvents but also in hydrophobic substrates and can be used as catalysts in chemical reactions in these hydrophobic media. These reactions proceed under very mild conditions, which enable us to apply PEG-enzymes to various organic syntheses of unstable or chiral compounds. Moreover, the enzymic reactions with high substrate specificity are suitable for the synthesis of various useful compounds. 

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