Application of Engineered biocatalysts for the synthesis of active pharmaceutical ingredients (APIs)

Juan Mangas-Sanchez, Sebastian C. Cosgrove and Nicholas J. Turner. Application of Engineered biocatalysts for the synthesis of active pharmaceutical ingredients (APIs) in Protein Engineering: tools and applications. pages 265-294. 2021 Wiley-VCH

The use of enzymes in organic synthesis features many advantages. For example, enzymes are highly selective and operate under mild reaction conditions. Furthermore, advances in molecular biology, metagenomics, and bioinformatics as well as increased speed of gene synthesis and sequencing have resulted in a great expansion of the field to cover a much broader range of transformations that are of increased value to synthetic chemists. These developments have encouraged large chemical and pharmaceutical companies to consider biocatalysis as a core technology rather than a last resort when all other options have failed. Nevertheless, the use of enzymes at industrial scale still possesses limitations. Reaction conditions in Nature are often mild and, therefore, enzymes have not been challenged to work under the conditions normally required in industry, i.e. organic solvents, high substrate loadings or non-physiological pH, or temperature. Moreover, they can present low catalytic efficiency toward substrates that are structurally distinct from the compound(s) they evolved to transform. They also often present exquisite chemo and stereoselectivity in highly functionalized molecules. Nevertheless, the enzyme may not have the desired selectivity, or the stereoselectivity on non-natural substrates may sometimes not be as high. Directed evolution (DE) approaches introduce genetic diversity in proteins, followed by screening for improved characteristics, and have been proven to be a powerful tool to tackle all these challenges. Consequently, over the last 20 years, DE and other rational approaches for protein engineering have been implemented by academic and industrial groups and nowa- days are routinely applied to improve enzyme performance. The impact that protein engineering has had on the chemistry community, and society as a whole, was underlined by the award of one-half of the 2018 Nobel Prize in Chemistry to Frances H. Arnold, for pioneering the use of DE to generate improved biocatalysts. In this chapter, we review recent examples of the use of engineered enzymes for the preparation of active pharmaceutical ingredients (APIs).