Discovery of a novel phosphotransferase from Bacillus subtilis that phosphorylates a broad spectrum of flavonoids

Abstract

Flavonoids are associated with health benefits, but most of them have poor oral bioavailability due to their extremely low aqueous solubility. Flavonoid O-phosphorylation suggests a potent modification to solve the problems. Here, we isolated, identified and characterized an unprecedented phosphotransferase, flavonoid phosphate synthetase (BsFPS), from B. subtilis. The enzyme catalyzes the ATP-dependent phosphorylation of flavonoid to generate flavonoid monophosphates, AMP and orthophosphate. BsFPS is a promiscuous phosphotransferase that efficiently catalyzes structurally-diverse flavonoids, including isoflavones, flavones, flavonols, flavanones and flavonolignans. Based on MS and NMR analysis, the phosphorylation mainly occurs on the hydroxyl group at C-7 of A-ring or C-4' of B-ring in flavonoid skeleton. Notably, BsFPS is regioselective for the ortho-3',4'-dihydroxy moiety of catechol-containing structures, such as luteolin and quercetin, to produce phosphate conjugates at C-4' or C-3' of B-ring. Our findings highlight the potential for developing biosynthetic platform to obtain new phosphorylated flavonoids for pharmaceutical and nutraceutical applications.

Keywords: 6-hydroxy flavone (PubChem CID: 72279); Bacillus subtilis; Biosynthesis; Flavonoid; Phenolic compounds; Phosphorylation; Phytochemicals; apigenin (PubChem CID: 5280443); daidzein (PubChem CID: 5281708); genistein (PubChem CID: 5280961); hesperetin (PubChem CID: 72281); kaempferol (PubChem CID: 5280863); luteolin (PubChem CID: 5280445); naringenin (PubChem CID: 932); quercetin (PubChem CID: 5280343); silybins A and B (PubChem CID: 3086637).