Comparison of the anion inhibition profiles of the beta- and gamma-carbonic anhydrases from the pathogenic bacterium Burkholderia pseudomallei

We report the cloning, purification and characterization of Bps beta CA, a beta-class carbonic anhydrase (CA, EC 4.2.1.1) from the pathogenic bacterium Burkholderia pseudomallei, the etiological agent of melioidosis, and compare its activity and inhibition with those of the gamma-CA from the same organism, Bps gamma CA, recently investigated by our groups. Bps beta CA showed a significant catalytic activity for the physiologic, CO2 hydration reaction, 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 x s(-1). The inhibition of Bps beta CA with a group of anions and small molecules was also investigated. The best inhibitors were sulfamide, sulfamic acid and phenylarsonic acid, which showed K(I)s in the range of 83-92 mu M, whereas phenylboronic acid, fluoride, cyanide, azide, bisulfite, tetraborate, perrhenate, perruthenate, peroxydisulfate, perchlorate, tetrafluoroborate, fluorosulfonate and hexafluorophosphate showed K(I)s > 100 mM. Other inhibitors of this new enzyme were bicarbonate, trithiocarbonate, some complex inorganic anions and N,N-diethyldithiocarbamate, which had inhibition constants of 0.32-8.6 mM. As little is known of the life cycle and virulence of this bacterium, this type of study may bring information of interest for the development of novel strategies to fight bacterial infection and drug resistance to commonly used antibiotics. (C) 2017 Elsevier Ltd. All rights reserved.