(469f) Combinatorial Biosynthesis of Pharmaceutically Important Simple Coumarins in Bacteria

Coumarins are a group of benzopyrone-type natural products that can be classified into four categories: simple coumarins, pyrone-substituted coumarins, furanocoumarins, and pyranocoumarins. Simple coumarins consist of the simplest coumarin skeleton (1,2-benzopyrone) and its hydroxylated, alkylated and glycosylated derivatives. Coumarins and their derivatives have demonstrated a vast array of therapeutical effects, such as antibacterial, anti-inflammatory and anti-coagulant activities. For instance, the well-known synthetic 4-hydroxycoumarin derivatives warfarin, phenprocoumon and acenocoumaroyl are among the most widely prescribed oral anticoagulants over the world. Moreover, extensive research into their pharmacological properties has revealed their therapeutic roles in the treatment of cancer and AIDS. Despite the pharmaceutical importance of coumarins, relatively limited information is available regarding their biosynthesis in nature. Couamrins are usually considered to be derived from the plant phenylpronanoid pathway; while the formation of 4-hydroxycoumarin (the synthetic precursor of warfarin) was prove to be the result of the infection of melilotoside-containing plant materials by molds. Here we present the development of novel biosynthetic mechanisms to produce several pharmaceutically important simple coumarins in Escherchia coli, including umbelliferone, scopoletin and 4-hydroxycoumarin. In this work, artificial biosynthetic pathways were designed, validated and optimized via combinatorial biosynthesis and metabolic engineering approaches. This work not only demonstrates promising application potentials, but also advances understanding of the chemistry in coumarin biosynthesis and lays the foundation for extending the pathways to produce more complicated coumarin derivatives for their biomedical and clinical property study.