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

Salivary carbonic anhydrase (CA VI) appears to protect teeth from caries vi a mechanisms other than direct regulation of salivary pH and buffering capa city. 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 hu man enamel pellicle. The study was performed using a specific rabbit antise rum to human CA VI in conjunction with immunostaining and immunoblot techni ques. CA activity was demonstrated using a histochemical staining method. C A VI immunostaining of extracted teeth having in vivo formed pellicle showe d that the enzyme is present in the enamel pellicle, Immunostaining for sal ivary 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 saliv a and solutions of purified enzyme. The intensity of the CA VI immunostaini ng on the enamel surface was dependent on the concentration of the applied enzyme. The histochemical staining of in vitro formed enamel pellicle confi rmed that the bound enzyme retains its enzymatic activity. The presence of active CA VI in the human enamel pellicle suggests that it may accelerate t he removal of acid by functioning locally in the pellicle layer on dental s urfaces.