Immobilized Metal Affinity Chromatography as a Drug Discovery Platform for Metalloenzyme Inhibitors

Immobilized metal-ion affinity chromatography (IMAC) used to purify recombinant proteins features a resin-bound 1:1 Ni­(II)–iminodiacetic acid (IDA) complex. This hemi-saturated Ni­(II)–IDA system containing exchangeable sites at the metal ion is re-cast as a surrogate of a coordinatively-unsaturated metalloenzyme active site, with utility for selecting compounds with metal-binding groups from mixtures as potential metalloenzyme inhibitors. Exchanging Ni­(II) for other metal ions could broaden the scope of metalloenzyme target. This work examined the performance of Cu­(II)-, Fe­(III)-, Ga­(III)-, Ni­(II)-, or Zn­(II)-IMAC resins to reversibly bind experimental or clinical metalloenzyme inhibitors of Zn­(II)-ACE1, Zn­(II)-HDAC, Fe­(II)/(III)-5-LO or Cu­(II)-tyrosinase from a curated mixture (1–17). Each IMAC system gave a distinct selection profile. The Zn­(II)-IMAC system selectively bound the thiol-containing Zn­(II)-ACE1 inhibitors captopril and omapatrilat, and the Fe­(III)-IMAC system selectively bound the Fe­(II)/(III)-5-LO inhibitor licofelone, demonstrating a remarkable IMAC-metalloenzyme metal ion match. IMAC provides a simple, water-compatible platform, which could accelerate metalloenzyme inhibitor discovery.