Anion inhibition studies of an α-carbonic anhydrase from the thermophilic bacterium Sulfurihydrogenibium yellowstonense YO3AOP1

The newly discovered thermophilic bacterium Sulfurihydrogenibium yellowstonense YO3AOP1 encodes an α-carbonic anhydrases (CAs, EC 4.2.1.1) which is highly catalytically active and thermostable. Here we report the inhibition of this enzyme, denominated SspCA, with inorganic and complex anions and other molecules interacting with zinc proteins. SspCA was inhibited in the micromolar range by diethyldithiocarbamate, sulfamide, sulfamic acid, phenylboronic and phenylarsonic acid, trithiocarbonate and selenocyanide (KIs of 4-70 μM) and in the submillimolar one by iodide, cyanide, (thio)cyanate, hydrogen sulfide, azide, nitrate, nitrite, many complex anions incorporating heavy metal ions and iminodisulfonate (KIs of 0.48-0.86 mM). SspCA was not substantially inhibited by bicarbonate and carbonate, hydrogensulfite and peroxidisulfate (KIs in the range of 21.1-84.6 mM). The exceptional thermostability and lack of strong affinity for hydrogensulfide, bicarbonate, and carbonate make this enzyme an interesting candidate for biotechnological applications of enzymatic CO2 fixation.