Salivary carbonic anhydrase isoenzyme VI is located in the human enamel pellicle

Salivary carbonic anhydrase (CA VI) appears to protect teeth from caries via mechanisms other than direct regulation of salivary pH and buffering capacity. To elucidate whether CA VI acts in the local microenvironment of the tooth surface, we studied the location and activity of the enzyme in the human enamel pellicle. The study was performed using a specific rabbit antiserum to human CA VI in conjunction with immunostaining and immunoblot techniques. CA activity was demonstrated using a histochemical staining method. CA VI immunostaining of extracted teeth having in vivo formed pellicle showed that the enzyme is present in the enamel pellicle. Immunostaining for salivary alpha-amylase, which is known to be present in the pellicle, showed a similar staining pattern. The presence of CA VI in the enamel pellicle was confirmed by immunoblotting of in vivo formed pellicle proteins. In vitro studies showed that CA VI binds to polished enamel surfaces from both saliva and solutions of purified enzyme. The intensity of the CA VI immunostaining on the enamel surface was dependent on the concentration of the applied enzyme. The histochemical staining of in vitro formed enamel pellicle confirmed that the bound enzyme retains its enzymatic activity. The presence of active CA VI in the human enamel pellicle suggests that it may accelerate the removal of acid by functioning locally in the pellicle layer on dental surfaces.