Carbonic anhydrase inhibitors: Inhibition of the transmembrane isozyme XIV with sulfonamides

The inhibition of the last human carbonic anhydrase (CA, EC 4.2.1.1) isozyme (hCA XIV) discovered has been investigated with a series of sulfonamides, including some clinically used derivatives (acetazolamide, methazolamide, ethoxzolamide, dichlorophenamide, dorzolamide, brinzolamide, benzolamide, and zonisamide), as well as the sulfamate antiepileptic drug topiramate. The full-length hCA XIV is an enzyme showing a medium-low catalytic activity, quite similar to that of hCA XII, with the following kinetic parameters at 20 degrees C and pH 7.5, for the CO2 hydration reaction: k(cat) = 3.12 x 10(5) s(-1) and k(cat)/K-M = 3.9 x 10(7) M-1 s(-1). All types of activities have been detected for the investigated compounds, with several micromolar inhibitors, including zonisamide, topiramate, and simple sulfanilamide derivatives (K-I-s in the range of 1.46-6.50 mu M). In addition, topiramate and zonisamide were observed to behave as weak hCA XII inhibitors, while zonisamide was an effective hCA IX inhibitor (K-I of 5.1 nM). Some benzene-1,3-disulfonamide derivatives or simple five-membered heteroaromatic sulfonamides showed K-I-s in the range of 180-680 nM against hCA XIV, whereas the most effective of such inhibitors, including 3-chloro-/bromo-sulfanilamide, benzolamide-like, ethoxzolamide-like, and acetazolamide/methazolamide-like derivatives, showed inhibition constant in the range of 13-48 nM. The best hCA XIV inhibitor was aminobenzolamide (K-I of 13 nM), but no CA XIV-selective derivatives were evidenced. There are important differences of affinity of these sulfonamides/sulfamates for the three transmembrane CA isozymes, with CA XII showing the highest affinity, followed by CA IX, whereas CA XIV usually showed the lowest affinity for these inhibitors. (c) 2005 Elsevier Ltd. All rights reserved.