Salt-activation of nonhydrolase enzymes for use in organic solvents

Enzymatic reactions are important for the synthesis of chiral molecules. One factor limiting synthetic applications of enzymes is the poor aqueous solubility of numerous substrates. To overcome this limitation, enzymes can be used directly in organic solvents; however, in nonaqueous media enzymes usually exhibit only a fraction of their aqueous-level activity. Salt-activation, a technique previously demonstrated to substantially increase the trans-esterification activity of hydrolytic enzymes in organic solvents, was applied to horse liver alcohol dehydrogenase, soybean peroxidase, galactose oxidase, and xanthine oxidase, which are oxicdoreductase and oxygenase enzymes. Assays of the Iyophilized enzyme preparations demonstrated that the presence of salt protected enzymes from irreversible inactivation. In organic solvents, there were significant increases in activity for the salt-activated enzymes compared to nonsalt-activatedcontrols for every enzyme tested. The increased enzymatic activity in organic solvents was shown to result from a combination of protection against inactivation during the freeze-drying process and other as-yet undetermined factors. (C) 2004 Wiley Periodicals,' Inc.