Carbonic anhydrase inhibitors: The X-ray crystal structure of ethoxzolamide complexed to human isoform II reveals the importance of thr200 and gln92 for obtaining tight-binding inhibitors

An X-ray crystallographic study for the binding of ethoxzolamide to human carbonic anhydrase (CA) II provides useful insights for the design of novel CA inhibitors targeting different isozymes. Ethoxzolamide, an almost forgotten inhibitor of the metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1), is the only classical inhibitor whose structure in adduct with any isoform was not reported yet. We report here the inhibition data of this molecule with the 12 catalytically active mammalian isozymes (CA I–CA XIV) and the X-ray crystal structure with the cytosolic, ubiquitous isoform CA II. These data are presumably useful for the design of novel CA inhibitors, targeting various CA isozymes, considering that ethoxzolamide was already the lead molecule to obtain the second generation inhibitors, dorzolamide and brinzolamide, clinically used antiglaucoma agents with topical action, as well as various other investigational agents.