Cloning, Characterization, and Inhibition Studies of a β‑Carbonic Anhydrase from Leishmania donovani chagasi, the Protozoan Parasite Responsible for Leishmaniasis

Leishmaniasis is an infection provoked by protozoans belonging to the genus Leishmania. Among the many species and subsepecies of such protozoa, Leishmania donovani chagasi causes visceral leishmaniasis. A β-carbonic anhydrase (CA, EC 4.2.1.1) was cloned and characterized from this organism, denominated here LdcCA. LdcCA possesses effective catalytic activity for the CO₂ hydration reaction, with <i>k</i>_cat of 9.35 × 10⁵ s^–1 and <i>k</i>_cat/K_M of 5.9 × 10⁷ M^–1 s^–1. A large number of aromatic/heterocyclic sulfonamides and 5-mercapto-1,3,4-thiadiazoles were investigated as LdcCA inhibitors. The sulfonamides were medium potency to weak inhibitors (<i>K</i>_I values of 50.2 nM–9.25 μM), whereas some heterocyclic thiols inhibited the enzyme with <i>K</i>_Is in the range of 13.4–152 nM. Some of the investigated thiols efficiently inhibited the in vivo growth of Leishmania chagasi and Leishmania amazonensis promastigotes, by impairing the flagellar pocket and movement of the parasites and causing their death. The β-CA from Leishmania spp. is proposed here as a new antileishmanial drug target