Carbonic anhydrase inhibitors: Cloning and sulfonamide inhibition studies of a carboxyterminal truncated α-carbonic anhydrase from Helicobacter pylori

A library of sulfonamides/sulfamates has been investigated for the inhibition of the carboxyterminal truncated form of the α-carbonic anhydrase (CA, EC 4.2.1.1) isolated from the gastric pathogen Helicobacter pylori (hpCA). This enzyme, incorporating 202 amino acid residues, showed a catalytic activity similar to that of the full length hpCA, with kcat of 2.35 × 105 s−1 and kcat/KM of 1.56 × 107 M−1 s−1 at 25 °C and pH of 8.9, for the CO2 hydration reaction. All types of activity for inhibition of the bacterial enzyme have been detected. Dorzolamide and simple 4-substituted benzenesulfonamides were weak hpCA inhibitors (inhibition constants, KIs, in the range of 830–4310 nM). Sulfanilamide, orthanilamide, some of their derivatives, and indisulam showed better activity (KIs in the range of 310–562 nM), whereas most of the clinically used CA inhibitors, such as methazolamide, ethoxzolamide, dichlorophenamide, brinzolamide, topiramate, zonisamide, etc., acted as medium potency hpCA inhibitors (KIs in the range of 124–287 nM). Some potent hpCA inhibitors were detected too (KIs in the range of 20–96 nM) such as acetazolamide, 4-amino-6-chloro-1,3-benzenedisulfonamide, 4-sulfanilyl-aminoethyl-benzenesulfonamide, and 4-(2-amino-pyrimidin-4-yl)-benzenesulfonamide. Most of the investigated derivatives acted as better inhibitors of the human isoform hCA II than as hpCA inhibitors. Since hpCA is essential for the survival of the pathogen in acid, its inhibition by compounds such as those investigated here might be used as a new pharmacologic tool in the management of drug resistant H. pylori.