Salivary Carbonic Anhydrase Isoenzyme VI Is Located in the Human Enamel Pellicle

Abstract

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 α–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.

Association of polymorphisms in the carbonic anhydrase 6 gene with salivary buffer capacity, dental plaque pH, and caries index in children aged 7–9 years

“…14 Bicarbonate ions can neutralize lactic and acetic acids produced by plaque bacteria and reduce demineralization. CAVI can adsorbs to the crystals of hydroxyapatite of enamel; 15 it is present in the enamel pellicle 16 and in dental biofilm. 17 Salivary buffer capacity seems to be a determinant factor on dental erosion, which is becoming a major dental problem in both children and adults.…”

Salivary carbonic anhydrase isoenzyme VI

“…Evaluation of the salivary buffer effect based on proteins has produced controversial results. In general the effect has been regarded as insignificant, or at least of minor importance, although data suggesting an alternative conclusion have also been presented (Leung, 1961;Izutsu & Madden, 1978 The existence of CA activity in human saliva has been known for 60 years (Becks & Wainwright, 1939), but until recently only a few studies had been carried out on the physiological role of salivary CA (Rapp, 1946;Szab o, 1974;Parkkila et al 1997;Kivel a et al 1997aKivel a et al , 1999Leinonen et al 1999). The ovine salivary CA isoenzyme expressed in the parotid gland was described in 1979 by Fernley et al The enzyme was purified from human saliva by Murakami & Sly (1987), and designated CA VI.…”

“…It is also thought to prevent calculus formation on the dental surfaces by controlling the precipitation of calcium phosphate from supersaturated saliva (Hay & Moreno, 1989). Recent research has indicated that CA VI binds to the enamel pellicle and retains its enzyme activity on dental surfaces (Leinonen et al 1999). In the enamel pellicle, CA VI is located at the optimal site to catalyse the conversion of salivary bicarbonate and microbe-delivered hydrogen ions to carbon dioxide and water (Fig.…”

Immunohistochemistry of the Bovine Secretory Carbonic Anhydrase Isozyme (CA-VI) in Bovine Alimentary Canal and Major Salivary Glands

“…With regard to the cytosolic CA isozymes, Asari et al [4] have already investigated well-known CA isozymes (CA-I, CA-II and CA-III) in bovine salivary glands and alimentary canal. The secretory CA-VI accelerates the neutralization of excess organic acids produced by microbial flora on dental and epithelial surfaces in the oral cavity and it forms a mutually complementary system with cytosolic CA for pH regulation in the upper alimentary canal [17,26]. CA-VI may be used for the control of pH and ion balance at the ruminant upper digestive tract in association with other CA isozymes.…”