Anion inhibition studies of the fastest carbonic anhydrase (CA) known, the extremo-CA from the bacterium Sulfurihydrogenibium azorense.

The α-carbonic anhydrase (CA, EC 4.2.1.1) from the extremophilic bacterium Sulfurihydrogenibium azorense, SazCA, is the fastest CA known to date as a catalyst for CO(2) hydration to bicarbonate and protons. We report an inhibition study of this enzyme with inorganic anions and several other small molecules known to interact with these metalloenzymes. Bicarbonate, carbonate and sulfate were ineffective SazCA inhibitors whereas most other inorganic anions were submillimolar inhibitors. The best inhibition was observed with trithiocarbonate, diethyldithiocarbamate, sulfamide, sulfamate, phenylboronic, and phenylarsonic acid, which showed inhibition constants in the range of 3-39 μM. As SazCA is very stable at high temperatures (being an 'extremo-CA') and very effective as a catalyst, the inhibition studies reported here may be crucial for designing biotechnological applications for this enzyme, for example for CO(2) capture processes.