Anion inhibition study of the β-class carbonic anhydrase (PgiCAb) from the oral pathogen Porphyromonas gingivalis.

The oral pathogenic bacterium Porphyromonas gingivalis, encodes for two carbonic anhydrase (CA, EC 4.2.1.1) one belonging to the β-class (PgiCAb) and another one to the γ-class (PgiCA). This last enzyme has been characterized earlier for its inhibition profile with various classes of CA inhibitors, such as the sulfonamides and anions, whereas for PgiCAb such data were not yet reported. Here we show that PgiCAb has a good catalytic activity for the CO2 hydration reaction, with kcat 2.8×10(5) s(-1) and kcat/Km of 1.5×10(7) M(-1) × s(-1), being inhibited by cyanate and diethyldithiocarbamate in the submillimolar range (KIs of 0.23-0.76 mM) and more efficiently by sulfamide, sulfamate, phenylboronic acid and phenylarsonic acid (KIs of 60-78 μM). The anion inhibition profile of the two P. gingivalis enzymes is very different. Identification of selective inhibitors of PgiCAb/PgiCA may lead to pharmacological tools useful for understanding the physiological role(s) of these enzymes, since this bacterium is the main causative agent of periodontitis and few treatment options are presently available.
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