Anion inhibition studies of two new β-carbonic anhydrases from the bacterial pathogen Legionella pneumophila

We investigated the cloning, catalytic activity and anion inhibition of the beta-class carbonic anhydrases (CAs, EC 4.2.1.1) from the bacterial pathogen Legionella pneumophila. Two such enzymes, lpCA(1) and lpCA(2), were found in the genome of this pathogen. These enzymes were determined to be efficient catalysts for CO2 hydration, with k(cat) values in the range of (3.4-8.3) x 10(5) s(-1) and k(cat)/K-M values of (4.7-8.5) x 10(7) M-1 s(-1). A set of inorganic anions and small molecules was investigated to identify inhibitors of these enzymes. Perchlorate and tetrafluoroborate were not acting as inhibitors (K-I > 200 mM), whereas sulfate was a very weak inhibitor for both lpCA(1) and lpCA(2) (KI values of 77.9-96.5 mM). The most potent lpCA(1) inhibitors were cyanide, azide, hydrogen sulfide, diethyldithiocarbamate, sulfamate, sulfamide, phenylboronic acid and phenylarsonic acid, with K-I values ranging from 6 to 94 mu M. The most potent lpCA(2) inhibitors were diethyldithiocarbamate, sulfamide, sulfamate, phenylboronic acid and phenylarsonic acid, with K-I values ranging from 2 to 13 mu M. As these enzymes seem to be involved in regulation of phagosome pH during Legionella infection, inhibition of these targets may lead to antibacterial agents with a novel mechanism of action. (C) 2014 Elsevier Ltd. All rights reserved.