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.