Spectroscopic and Biochemical Characterization of Metallo-β-lactamase IMP-1 with Dicarboxylic, Sulfonyl, and Thiol Inhibitors

In an effort to probe the biophysical mechanisms of inhibition for ten previously-reported inhibitors of metallo-β-lactamases (MBL) with MBL IMP-1, equilibrium dialysis, metal analyses coupled with atomic absorption spectroscopy (AAS), native state mass spectrometry (native MS), and ultraviolet-visible spectrophotometry (UV-VIS) were used. 6-(1H-tetrazol-5-yl) picolinic acid (1T5PA), ANT431, D/l-captopril, thiorphan, and tiopronin were shown to form IMP-1/Zn(II)/inhibitor ternary complexes, while dipicolinic acid (DPA) and 4-(3-aminophenyl)pyridine-2,6-dicarboxylic acid (3AP-DPA) stripped some metal from the active site of IMP but also formed ternary complexes. DPA and 3AP-DPA stripped less metal from IMP-1 than from VIM-2 but stripped more metal from IMP-1 than from NDM-1. In contrast to a previous report, pterostilbene does not appear to bind to IMP-1 under our conditions. These results, along with previous studies, demonstrate similar mechanisms of inhibition toward different MBLs for different MBL inhibitors.