Anion inhibition profiles of the complete domain of the eta-carbonic anhydrase from Plasmodium falciparum

We have cloned, purified and investigated the catalytic activity and anion inhibition profiles of a full catalytic domain (358 amino acid residues) carbonic anhydrase (CA, EC 4.2.1.1) from Plasmodium falciparum, PfCAdom, an enzyme belonging to the eta-CA class and identified in the genome of the malaria-producing protozoa. A truncated such enzyme, PfCA1, containing 235 residues was investigated earlier for its catalytic and inhibition profiles. The two enzymes were efficient catalysts for CO2 hydration: PfCAdom showed a k(cat) of 3.8 x 10(5) s(-1) and k(cat)/K-m of 7.2 x 10(7) M-1 x s(-1), whereas PfCA showed a lower activity compared to PfCAdom, with a k(cat) of 1.4 x 10(5) s(-1) and k(cat)/K-m of 5.4 x 10(6) M-1 x s(-1). PfCAdom was generally less inhibited by most anions and small molecules compared to PfCA1. The best PfCAdom inhibitors were sulfamide, sulfamic acid, phenylboronic acid and phenylarsonic acid, which showed K(I)s in the range of 9-68 mu M, followed by bicarbonate, hydrogensulfide, stannate and N, N-diethyldithiocarbamate, which were submillimolar inhibitors, with K(I)s in the range of 0.53-0.97 mM. Malaria parasites CA inhibition was proposed as a new strategy to develop antimalarial drugs, with a novel mechanism of action. (C) 2016 Elsevier Ltd. All rights reserved.