Abstract
Among the numerous metalloenzymes known to date, carbonic anhydrase (CA, EC 4.2.1.1) was the first zinc containing one, being discovered decades ago. CA is a hydro-lyase, which catalyzes the following hydration-dehydration reaction: CO2 + H2O (sic) HCO3 + H+. Several CA classes are presently known, including the alpha-, beta-, gamma-, delta-, zeta- and eta-CAs. In prokaryotes, the existence of genes encoding CAs from at least three classes (alpha-, beta- and gamma-class) suggests that these enzymes play a key role in the physiology of these organisms. In many bacteria CAs are essential for the life cycle of microbes and their inhibition leads to growth impairment or growth defects of the pathogen. CAs thus started to be investigated in detail in bacteria, fungi and protozoa with the aim to identify antiinfectives with a novel mechanism of action. Here, we investigated the catalytic activity, biochemical properties and anion inhibition profiles of the three CAs from the bacterial pathogen Vibrio cholera, VchCA, VchCA beta and VchCA gamma. The three enzymes are efficient catalysts for CO2 hydration, with k(cat) values ranging between (3.4 - 8.23) x 10(5) s (1) and k(cat)/K-M of (4.1 - 7.0) x 10(7) M (1) s (1). A set of inorganic anions and small molecules was investigated for inhibition of these enzymes. The most potent VchCA gamma inhibitors were N,N-diethyldithiocarbamate, sulfamate, sulfamide, phenylboronic acid and phenylarsonic acid, with K-I values ranging between 44 and 91 mu M. (C) 2016 Elsevier Ltd. All rights reserved.