Carbonic anhydrase inhibitors. Inhibition of the β-class enzyme from the yeast Saccharomyces cerevisiae with anions

The protein encoded by the Nce103 gene of Saccharomyces cerevisiae, a β-carbonic anhydrase (CA, EC 4.2.1.1) designated as scCA, has been cloned, purified, characterized kinetically, and investigated for its inhibition with a series simple, inorganic anions such as halogenides, pseudohalogenides, bicarbonate, carbonate, nitrate, nitrite, hydrogen sulfide, bisulfite, perchlorate, sulfate, and some of its isosteric species. The enzyme showed high CO2 hydrase activity, with a kcat of 9.4 × 105 s−1 and kcat/Km of 9.8 × 107 M−1 s−1. scCA was weakly inhibited by metal poisons (cyanide, azide, cyanate, thiocyanate, KIs of 16.8-55.6 mM) and strongly inhibited by bromide, iodide, and sulfamide (KIs of 8.7-10.8 μM). The other investigated anions showed inhibition constants in the low millimolar range.