Comparison of the Sulfonamide Inhibition Profiles of the - and -Carbonic Anhydrases from the Pathogenic Bacterium Burkholderia pseudomallei

We have cloned, purified, and characterized a -carbonic anhydrase (CA, EC 4.2.1.1), BpsCA, from the pathogenic bacterium Burkholderia pseudomallei, responsible for the tropical disease melioidosis. The enzyme showed high catalytic activity for the physiologic CO2 hydration reaction to bicarbonate and protons, with the following kinetic parameters: k(cat) of 1.6 x 10(5) s(-1) and k(cat)/K-M of 3.4 x 10(7) M-1 s(-1). An inhibition study with a panel of 38 sulfonamides and one sulfamateincluding 15 compounds that are used clinicallyrevealed an interesting structure-activity relationship for the interaction of this enzyme with these inhibitors. Many simple sulfonamides and clinically used agents such as topiramate, sulpiride, celecoxib, valdecoxib, and sulthiame were ineffective BpsCA inhibitors (K-I > 50 mu M). Other drugs, such as ethoxzolamide, dorzolamide, brinzolamide, zonisamide, indisulam, and hydrochlorothiazide were moderately potent micromolar inhibitors. The best inhibition was observed with benzene-1,3-disulfonamidesbenzolamide and its analogs acetazolamide and methazolamidewhich showed K-I in the range of 185-745 nM. The inhibition profile of BpsCA is very different from that of the -class enzyme from the same pathogen, BpsCA. Thus, identifying compounds that would effectively interact with both enzymes is relatively challenging. However, benzolamide was one of the best inhibitors of both of these CAs with K-I of 653 and 185 nM, respectively, making it an interesting lead compound for the design of more effective agents, which may be useful tools for understanding the pathogenicity of this bacterium.