Phage display as a tool for the directed evolution of enzymes

Since its introduction in 1985, phage display has had a tremendous impact on the discovery of peptides that bind to a variety of receptors, the generation of binding sites within predefined scaffolds, and the creation of high-affinity antibodies without immunization. Its application to enzymology has required the development of techniques that couple enzymatic activity to selection protocols based on affinity chromatography. Here, we describe both indirect methods, using transition-state analogues and suicide substrates, and direct methods, using the ability of active phage-enzymes; to transform substrate into product. The methods have been applied to large libraries for mechanistic-based studies and to generate variants with new or improved properties. In addition, such techniques have been successfully used to select catalytic antibodies and improve their catalytic efficiency.