Enzyme engineering: rational redesign versus directed evolution

Enzyme engineering is undergoing the most profound and exciting transformat ion in its history(1). It promises unprecedented expansion in the scope and applications of modified or improved enzymes with desired physical and cat alytic properties. Two complementary strategies are currently available: ra tional redesign(2-5) and directed evolution(6,7). Although both approaches have met with great success, each has limitations. In this article, the per spectives for these enzyme-engineering strategies are discussed briefly.