Design and evolution of enzymes for non-natural chemistry

Enzymes are used in biocatalytic processes for the efficient and sustainable production of pharmaceuticals, fragrances, fine chemicals, and other products. Most bioprocesses exploit chemistry found in nature, but we are now entering a realm of biocatalysis that goes well beyond. Enzymes have been engineered to catalyze reactions previously only accessible with synthetic catalysts. Because they can be tuned by directed evolution, many of these new biocatalysts have been shown to perform abiological reactions with high activity and selectivity. We discuss recent examples, showcase catalyst improvements achieved using directed evolution, and comment on some current and future implications of nonnatural enzyme evolution for sustainable chemical synthesis.