Poly(ethylene glycol)-α-chymotrypsin complex catalytically active in anhydrous isooctane

Enzymatic catalysis in predominantly organic media has undergone rapid expansions, particularly over the past decade. There are numerous potential advantages in employing enzymes in organic media. However, there are some crucial defects in the native enzyme-catalyzed biocatalyses, such as a decrease in their reaction rate due to diffusional limitations of substrates. To overcome these defects, enzymes modified chemically with polymers and physically with surfactants, which were soluble in organic solvents, were often used. However, they had inherent drawbacks. On the other hand, the enzymes modified physically with polymers were found to be soluble and catalytically active in organic media. To date, however, the effect of the amount of added polymers on the enzyme activity has not been clarified, even though this may be an important factor governing the activity of polymer-enzyme complexes in organic media. In this study, we obtained a complex of an enzyme and a hydrophilic polymer by lyophilizing an aqueous solution containing a polymer and an enzyme. We found that the polymer-enzyme complex was catalytically active in organic media even when the molar ratio of polymer/enzyme in its preparation stage was unity, and that the activity of the polymer-enzyme complex increased with an increase in the molar ratio of polymer/enzyme, reached the maximum activity (ca. 7200-fold higher than that of the native enzyme suspended in organic media) and then gradually decreased.