Two new β-carbonic anhydrases (CAs, EC 4.2.1.1) from the bacterial pathogen Salmonella enterica serovar Typhimurium, stCA 1 and stCA 2, were characterized kinetically. The two enzymes possess appreciable activity as catalysts for the hydration of CO(2) to bicarbonate, with k(cat) of 0.79×10(6) s(-1) and 1.0×10(6) s(-1), and k(cat)/K(m) of 5.2×10(7) M(-1) s(-1) and of 8.3×10(7) M(-1) s(-1), respectively. A large number of simple/complex inorganic anions as well as other small molecules (sulfamide, sulfamic acid, phenylboronic acid, phenylarsonic acid, dialkyldithiocarbamates) showed interesting inhibitory properties towards the two new enzymes, with several low micromolar inhibitors discovered. As many strains of S. enterica show extensive resistance to classical antibiotics, inhibition of the β-CAs investigated here may be useful for developing lead compounds for novel types of antibacterials.
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