Synthetic biology has enabled the production of natural and unnatural products from inexpensive sustainable feedstocks. Yet, the scope of available products has been limited largely to compounds accessible from nature's chemical reactions. Evolved enzymes can catalyse reactions of unnatural substrates or reactions not found in nature but often require the addition of synthetic reagents to purified enzymes or to resting cells containing those enzymes. Here we show that chemical reactions of metabolic intermediates produced intracellularly in living cells can include intermolecular nitrene transfers. The biosynthesis of N-acetoxyanilines, in combination with the generation and transfer of N-aryl nitrene intermediates from them catalysed by a cytochrome P450, generates amino alcohols, diamines, diarylamines and aminoalkyl arenes from simple carbon feedstocks. These products-common substructures of pharmaceuticals and agrochemicals-are challenging to synthesize by standard organic chemistry and were produced from inexpensive, renewable feedstocks. Evolution of the enzymes in this pathway showed that titres can be increased by engineering and that the products can be synthesized with high enantioselectivity.
Isaac Donnell, Andrew Quest, Jeremy Tang et al.· Nature Chemistry· 0 citations
Coumarins and their derivatives possess diverse bioactivities and broad applications in pharmaceuticals, food additives, and materials science. For example, amino-functionalized coumarin derivatives hold significant promise for the development of novel functional materials and drug discovery. However, the microbial biosynthesis of these compounds remains underexplored. In this study, we characterized the substrate flexibility of the type III polyketide synthase PqsD from Pseudomonas aeruginosa in Pseudomonas putida KT2440, showing its ability to convert various para- and meta-substituted salicylic acids into novel coumarin derivatives. Leveraging the substrate promiscuity of PqsD, we established a novel microbial route to produce 6-amino-4-hydroxycoumarin (6A4HC). Furthermore, we developed a new de novo biosynthetic route for its direct precursor, 5-aminosalicylic acid (5ASA), which is an FDA-approved pharmaceutical compound. This work expands the enzymatic toolbox for coumarin biosynthesis and highlights microbial platforms as sustainable alternatives for generating structurally diverse and functionalized coumarins.
