Biosynthesis of Rhamnosylated Anthraquinones in Escherichia coli

Rhamnose is a naturally occurring deoxy sugar present as a glycogenic component of plant and microbial natural products. A recombinant mutant strain was developed by overexpressing genes involved in TDP-rhamnose biosynthesis pathway of different bacterial strains and rhamnosyl transferase to conjugate intrinsic cytosolic TDP-L-rhamnose with anthraquinones supplemented exogenously. Among the five anthraquinones (alizarin, emodin, chrysazin, anthrarufin, and quinizarin) tested, quinizarin was biotransformed to rhamoside derivative with the highest conversion ratio by the whole cells of engineered . The quinizarin glycoside was identified by various chromatographic and spectroscopic analyses. The anti-proliferative property of the newly synthesized rhamnoside, quinizarin-4--α-L-rhamnoside was assayed in various cancer cells.