Extended Data Fig. 4: Mössbauer spectra of the PolF reaction using l-[U-D8]Val as a substrate.
From: Azetidine amino acid biosynthesis by non-haem iron-dependent enzymes
![Extended Data Fig. 4: Mössbauer spectra of the PolF reaction using l-[U-D8]Val as a substrate.](http://media.springernature.com/full/springer-static/esm/art%3A10.1038%2Fs41557-025-01958-x/MediaObjects/41557_2025_1958_Fig10_ESM.jpg?as=webp)
Spectra were acquired at 4.2 K in a 53-mT magnetic field externally applied parallel to the propagation direction of the γ beam. The experimental spectra are depicted by vertical bars of heights reflecting the standard deviations of the absorption values during the acquisition of the spectra. The top spectra (i) in each panel is that of an anoxic solution of the reactant complex (1.44 mM PolF, 2.88 mM 57Fe(II), and 40 mM [U-D8]Val). Spectra ii – v are the reactions initiated by mixing the anoxic solution with O2 saturated buffer and incubated at 5 °C for the time shown in the figure. Shown at the bottom is the difference spectra (iii - i) overlaid with their simulations with quadrupole doublets, demonstrating the formation of μ-peroxo-Fe(III)2 (blue trace: δ = 0.58 mm/s, and ΔEQ = 1.26 mm/s) in expense of the consumption of high-spin Fe(II)2 (red trace: δ = 1.23 mm/s and ΔEQ = 2.65 mm/s). Peak quantitation revealed 32, 51, and 49% of total Fe is associated with μ-peroxo-Fe(III)2. Spectrum v (30 min incubation) is dominated by the broad, magnetically split features associated with mononuclear high-spin Fe(III) ( ~ 80% of total intensity), in addition to the quadrupole doublet associated with the non-reactive Fe(II) complex(es) at δ = ~0 mm/s and ~3 mm/s (~20% of total intensity), suggesting the cluster destruction as observed in other HDO enzymes.
