The oral pathogenic bacterium Porphyromonas gingivalis, encodes for two carbonic anhydrases (CAs, EC 4.2.1.1) one belonging to the γ-class (PgiCA) and another one to the β-class (PgiCAb). This last enzyme has been cloned and characterized here for its inhibition profile with the main class of CA inhibitors, the sulfonamides. Many of the clinically used sulfonamides as well as simple aromatic/heterocyclic sulfonamides were ineffective as PgiCAb inhibitors whereas better inhibition was observed with simple derivatives such as sulfanilamide, metanilamide, 4-aminoalkylbenzenesulfonamides (KIs of 364-475nM). The halogenosulfanilamides incorporating heavy halogens, 4-hydroxy- and 4-hydroxyalkyl-benzenesulfonamides, were also micromolar, ineffective PgiCAb inhibitors. The best inhibitors of the β-class enzyme were acetazolamide and ethoxzolamide, with KIs of 214-280nM. Interestingly, the γ-class enzyme was much more sensitive to sulfonamide inhibitors compared to the β-class one, PgiCAb. Identification of potent and possibly 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.