A Microbial Cell Factory Combining an Artificial Metathase with a Fatty Acid Decarboxylase for New-to-Nature Synthesis of Cycloalkenes

Abstract Artificial metalloenzymes (ArMs) are powerful tools for catalyzing new-to-nature reactions. ArMs offer great potential to complement natural enzymes in concurrent cascade reactions. For in cellulo applications, however, the abundance of thiols in the cytosol of aerobic organisms limits the use of ArMs that rely on precious metal cofactors. To overcome this limitation, compartmentalization of ArMs either in the periplasm or on the surface of Escherichia coli has shown promise. We report herein on our efforts to combine a surface-displayed artificial metathase with UndB, an inner membrane decarboxylase. The resulting concurrent cascade converts medium-chain dicarboxylates to cyclic alkenes. To optimize the cascade, we evolved both enzymes independently and fine-tuned their relative expression levels. Compared to the wild-type whole-cell enzyme cascade, the engineered strain was improved by > 75-fold for the conversion of sebacic acid to cyclohexene. To the best of our knowledge, this represents the first example of a whole-cell enzyme cascade that combines a natural enzyme with an ArM.