Fig. 4. 31P NMR spectra of the incubation of His6–FzmG with PnAA. (A) NMR spectrum of the reaction mixture containing PnAA, O2, α-KG, Fe(ii), l-ascorbate, and His6–FzmG. (B) NMR spectrum of the enzymatic reaction mixture spiked with authentic standard of PnAA. (C) NMR spectrum of the reaction mixture spiked with authentic standards of PnAA and PnA. (D) NMR spectrum of the reaction mixture in the absence of His6–FzmG. The chemical shifts of phosphonates in 31P NMR are very sensitive to pH near their pKa values, accounting for the changes in chemical shifts between experiments and requiring spiking with standards for assignments.
