Cloning, Characterization, and Sulfonamide and Thiol Inhibition Studies of an α‑Carbonic Anhydrase from <i>Trypanosoma cruzi</i>, the Causative Agent of Chagas Disease

Abstract

An α-carbonic anhydrase (CA, EC 4.2.1.1) has been identified, cloned, and characterized from the unicellular protozoan <i>Trypanosoma cruzi</i>, the causative agent of Chagas disease. The enzyme (TcCA) has a very high catalytic activity for the CO₂ hydration reaction, being similar kinetically to the human (h) isoform hCA II, although it is devoid of the His64 proton shuttle. A large number of aromatic/heterocyclic sulfonamides and some 5-mercapto-1,3,4-thiadiazoles were investigated as TcCA inhibitors. The aromatic sulfonamides were weak inhibitors (<i>K</i>_I values of 192 nM to 84 μM), whereas some heterocyclic compounds inhibited the enzyme with <i>K</i>_I values in the range 61.6–93.6 nM. The thiols were the most potent in vitro inhibitors (<i>K</i>_I values of 21.1–79.0 nM), and some of them also inhibited the epimastigotes growth of two <i>T. cruzi</i> strains in vivo