Fig. 2: Biochemical characterization of the flavin-dependent monooxygenase VibO expressed in E. coli as a soluble protein.

a LC-MS analyses of in vitro activities of VibO, using the reaction of heat-inactivated enzyme as control. The extracted ion traces of m/z 231 are corresponding to [M + Na]⁺ of 3, 3′, 7 and [M + K]⁺ of 6, respectively; m/z 215 is for 6 [M + Na]⁺; m/z 207 is for 7 [M−H]⁻. 3′ is an oxepin-2(7H)-one isomer of 3 (see Fig.6a). A trace of 3′ remains as impurity in isolation of compound 7. b Reaction schemes of VibO. c Dependence of 3 and 7 production on NADPH (0 to 10 mM). The yield was estimated from peak area ratios of the product to the internal standard. The columns represent accumulation of products (the highest mean value was set 100%); bars indicate ± SD (standard deviation) of three replicates. Source data are provided as a Source Data file. d Mass spectra of VibO-formed 3 in ¹⁸O₂ /H₂O, O₂ /H₂¹⁸O, O₂ /D₂O (deuterated), and the normal O₂ /H₂O buffer systems. The original data are provided in Supplementary Figs. 5−11, 15−18.