In Vivo Biocatalytic Cascades Featuring an Artificial‐Enzyme‐Catalysed New‐to‐Nature Reaction**

Artificial enzymes utilizing the genetically encoded non-proteinogenic amino acid p-aminophenylalanine (pAF) as a catalytic residue are able to react with carbonyl compounds through an iminium ion mechanism promote reactions that have no equivalent in nature. Herein, we report vivo biocatalytic cascade is augmented such artificial enzyme-catalysed new-to-nature reaction. The enzyme this study pAF-containing evolved variant of lactococcal multidrug-resistance regulator, designated LmrR_V15pAF_RMH, which efficiently converts benzaldehyde derivatives produced into corresponding hydrazone products inside E. coli cells. These cascades comprising artificial-enzyme-catalysed reaction important step towards achieving hybrid metabolism.