FIG 6.

Characterization of the N-acetyltransferase activity of PmvE with putrescine (A) and spermine (B) as substrates by high-resolution HPLC-ESI-MS. Extracted ion current (XIC) profiles were registered between 0 and 5 min, and related ESI spectra were analyzed. (A) (Left) The ion at 89.12 m/z corresponds to the theoretical m/z value of the [M + 1H]⁺¹ putrescine. (Right) The ion at 131.12 m/z corresponds to the theoretical m/z value of the [M + 1H]⁺¹ acetylated putrescine. (B) (Left) The ion at 203.22 m/z corresponds to the theoretical m/z value of the [M + 1H]⁺¹ spermine. (Right) The ion at 245.22 m/z corresponds to the theoretical m/z value of the [M + 1H]⁺¹ acetylated spermine. NL, normalization level; RT, retention time.