A β-class carbonic anhydrase (CA, EC 4.2.1.1) from the pathogenic bacterium Francisella tularensis (FtuβCA) was cloned and purified, and the anion inhibition profile was investigated. Based on the measured kinetic parameters for the enzyme catalyzed CO2 hydration reaction (kcat of 9.8×105s-1 and a kcat/KM of 8.9×107M-1s-1), FtuβCA is a highly effective enzyme. The activity of FtuβCA was not inhibited by a range of anions that do not typically coordinate Zn(II) effectively, including perchlorate, tetrafluoroborate, and hexafluorophosphate. Surprisingly, some anions which generally complex well with many cations, including Zn(II), also did not effectively inhibit FtuβCA, e.g., fluoride, cyanide, azide, nitrite, bisulphite, sulfate, tellurate, perrhenate, perrhuthenate, and peroxydisulfate. However, the most effective inhibitors were in the range of 90-94µM (sulfamide, sulfamic acid, phenylarsonic and phenylboronic acid). N,N-Diethyldithiocarbamate (KI of 0.31mM) was a moderately potent inhibitor. As Francisella tularensis is the causative agent of tularemia, the discovery of compounds that can interfere with the life cycle of this pathogen may result in novel opportunities to fight antibiotic drug resistance.
Keywords: Anions; CA inhibitors; Carbonic anhydrase; Francisella tularensis; Tularemia; β-Class.
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