Diversifying humanity’s toolkit of green catalysts

: Exploring and expanding the natural diversity of imine-reducing enzymes

Abstract

Enzymes might be a game-changer in the quest for sustainable industrial processes, offering a greener alternative to traditional chemical methods. Natural diversity holds the key by providing a diverse yet extendable biocatalytic toolkit. Amongst others, imine-reducing enzymes have gained attention in recent years as promising biocatalysts for the synthesis of chiral amines. Particularly, the pharmaceutical industry is interested in their application for the enantiopure synthesis. The broad range of chiral amine-containing building blocks and active pharmaceutical substances, along with varying process requirements (e.g., temperature, solvent, or pH stability), underlines the need for considering a preferably large share of the natural diversity. Although several enzyme families of different structural archetypes catalyse the same reaction, previous research was focused on the family of imine reductases (IREDs). Possibly disregarded by less explicit and delusive classifications, the families of short-chain dehydrogenases/reductases (SDRs) and β-hydroxy acid dehydrogenases (βHADs) still offer unexploited potential in providing catalysts for the same reaction. In the presented body of work, bioinformatical and structure-guided analysis was performed on these three enzyme families to extract common structural and biochemical features. The knowledge obtained from this analysis was used for rational enzyme engineering, resulting in the artificial introduction of imine-reducing activities in SDRs and βHADs. Based on these findings, the herein presented outputs are supplemented by evolutionary, thermodynamical, and philosophical considerations reflecting the role of enzyme promiscuity. Further, potentially valuable implications on enzyme engineering and discovery are derived and formulated into a strategic decision tree. Finally, the work is placed in a larger context and its limits and potentials are reflected.

Date of Award	Feb 2024
Original language	English
Awarding Institution	Coventry University
Supervisor	James Dayus (Supervisor) & Sebastien Farnaud (Supervisor)