Cloning, purification, kinetic and anion inhibition studies of a recombinant β-carbonic anhydrase from the Atlantic salmon parasite platyhelminth Gyrodactylus salaris

A β-class carbonic anhydrase (CA, EC 4.2.1.1) was cloned from the genome of the Monogenean platyhelminth Gyrodactylus salaris, a parasite of Atlantic salmon. The new enzyme, GsaCAβ has a significant catalytic activity for the physiological reaction, CO 2 + H 2 O ⇋ HCO 3 − + H + with a k cat of 1.1 × 10 5 s −1 and a k cat /K m of 7.58 × 10 6 M −1 × s −1 . This activity was inhibited by acetazolamide (K I of 0.46 µM), a sulphonamide in clinical use, as well as by selected inorganic anions and small molecules. Most tested anions inhibited GsaCAβ at millimolar concentrations, but sulfamide (K I of 81 µM), N,N-diethyldithiocarbamate (K I of 67 µM) and sulphamic acid (K I of 6.2 µM) showed a rather efficient inhibitory action. There are currently very few non-toxic agents effective in combating this parasite. GsaCAβ is subsequently proposed as a new drug target for which effective inhibitors can be designed.