Interaction of anions with a newly characterized alpha carbonic anhydrase from Halomonas sp

The inhibition and characterization of the α-class carbonic anhydrase (CA, EC 4.2.1.1) from the Halomonas sp. are reported for the first time. The enzyme was purified 91-fold with a yield of 39%, and a specific activity of 600 U/mg proteins was obtained. It has an optimum pH at 7.5, an optimum ionic strength at 20 mM and an optimum temperature at 20 °C. The following anions, SCN(-), Br(-), Cl(-), I(-), [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] showed inhibitory effects on the hydratase activity of the enzyme. Sulfate, sulfide, azide, nitrate, nitrite and iodide exhibited the strongest inhibitory activity, in the micromolar range (KI-s of 5.5-15.5 µM). SCN(-), Br(-), Cl(-), [Formula: see text] were moderate inhibitors, whereas other anions showed only weak activities. Our findings indicate that these anions inhibit the Halomonas sp. CA (HmCA) enzyme in a similar manner to other α-CAs from mammals investigated earlier, but the susceptibility to various anions differs significantly between the Halomonas sp. and other organism CAs.