Mass spectrometric analysis results for MMNAT and TBNAT after incubation with the piperidinol inhibitors.

For the ESI-MS studies, samples of each enzyme (0.07 mM in 20 mM Tris-HCl, pH 8.0 and 5–10% (v/v) DMSO) were incubated with the different inhibitors at an enzyme-to-inhibitor molar ratio of either 1∶1 or 1∶15 at 24°C for 30–60 min. Confidence intervals are ±8–12 Da. Samples of each enzyme alone (in the same buffer) were analysed in the same way as the controls and used to calculate the mass difference upon incubation with the inhibitor (Δm values). mpvk is the mass of the expected phenyl-oxopropyl fragments of 132 Da for 1, 3, 4 and 5, or 166 Da for 2 and identifies the number of modifications. The Molar ratio refers to the proposed number of inhibition species bound per protein molecule. Cys refers to the number of cysteine residues in the sequence. See Methods for further experimental details.