Challenges in capturing oxygenase activity in vitro

Biocatalysis using oxygenase or desaturase enzymes has the potential to add value to native fats and oils by adding oxygen, hydroxyl groups, or double bonds to create regio- and/or stereospecific products. These enzymes are a subset of the large class of oxidoreductase enzymes (from EC subgroups 1.1 3 and 1.14) involved with biological oxidation and reduction. In vitro bioc atalytic processing using these enzymes is hampered by the high cost of the stoichiometric cofactors. This article reviews recent progress in developi ng in vitro redox enzyme biocatalysis for commercial-scale syntheses. Coenz yme recycling and electrochemical redox cycling as methods for cofactor reg eneration are described and commercial applications indicated. Direct charg e transfer without use of mediators is described as the cleanest way of int roducing the reducing power into the catalytic cycle. Our electrochemically driven cytochrome P450(cam) bioreactor is discussed as an example of direc t charge transfer to a redox protein. Site-directed mutagenesis in the acti ve site of the P450(cam) monooxygenase greatly improved performance for the conversion of the nonnative substrate, styrene to styrene oxide. This epox idation reaction was also shown to give a single product (styrene oxide) in the bioelectrochemical reactor when the diatomic oxygen co-substrate was m anaged properly.