Characterization of the aminocoumarin ligase SimL from the simocyclinone pathway and tandem incubation with NovM,P,N from the novobiocin pathway

Simocyclinone D₈ consists of an anguicycline C-glycoside tethered by a tetraene diester linker to an aminocoumarin. Unlike the antibiotics novobiocin, clorobiocin, and coumermycin A₁, the phenolic hydroxyl group of the aminocoumarin in simocyclinone is not glycosylated with a decorated noviosyl moiety that is the pharmacophore for targeting bacterial DNA gyrase. We have expressed the Streptomyces antibioticus simocyclinone ligase SimL, purified it from Escherichia coli, and established its ATP-dependent amide bond forming activity with a variety of polyenoic acids including retinoic acid and fumagillin. We have then used the last three enzymes from the novobiocin pathway, NovM, NovP, and NovN, to convert a SimL product to a novel novobiocin analogue, in which the 3-prenyl-4-hydroxybenzoate of novobiocin is replaced with a tetraenoate moiety, to evaluate antibacterial activity.