Escherichia coli γ-carbonic anhydrase: characterisation and effects of simple aromatic/heterocyclic sulphonamide inhibitors

Carbonic anhydrases (CAs, EC 4.2.1.1) are ubiquitous metalloenzymes involved in biosynthetic processes, transport, supply, and balance of CO2/HCO(3)(-)into the cell. In Bacteria, CAs avoid the depletion of the dissolved CO2/HCO(3)(-)from the cell, providing them to the central metabolism that is compromised without the CA activity. The involvement of CAs in the survival, pathogenicity, and virulence of several bacterial pathogenic species is recent. Here, we report the kinetic properties of the recombinant gamma-CA (EcoCA gamma) encoded in the genome ofEscherichia coli. EcoCA gamma is an excellent catalyst for the physiological CO(2)hydration reaction to bicarbonate and protons, with a k(cat)of 5.7 x 10(5) s(-1)and k(cat)/K(M)of 6.9 x 10(6) M(-1)s(-1). The EcoCA gamma inhibition profile with a broad series of known CA inhibitors, the substituted benzene-sulphonamides, and clinically licenced drugs was explored. Benzolamide showed a K(I)lower than 100 nM. Our study reinforces the hypothesis that the synthesis of new drugs capable of interfering selectively with the bacterial CA activity, avoiding the inhibition of the human alpha-CAs, is achievable and may lead to novel antibacterials.