Phosphoric monoester hydrolase-like activity in the odontoblast-predentine region of intact and carious human teeth

Abstract

Coronal odontoblast-predentine tissue was taken from intact teeth and from teeth with various types of occlusal caries, and the specific phosphoric monoester hydrolase activity in the non-sedimentable (20,200 g ) fraction was measured at alkaline and acid pH, using p-nitrophenyl phosphate as a substrate. A significant increase of activity similar to alkaline phosphatase (AlPase) was observed under enamel and initial dentine caries lesions. The enzyme activity was about equal to that of the intact tissue when the overlying lesions were arrested, subsiding significantly where large advanced lesions were concerned. As AlPase-like activity was maximal in active enamel and initial dentine lesions, it was concluded that the enzyme has an important role in protein matrix formation. The activity of acid phosphatase (AcPase) was approximately 10–15 times weaker than that of AlPase in the intact odontoblast-predentine area and was increased under advanced dentine lesions. The appearance of AcPase-like activity probably indicated metabolic changes related to reparative dentine formation and partly reflected the level of degradation of severely injured odontoblasts by the autolytic release of lysosomal enzymes. The phosphoric monoester hydrolases both in intact and in carious teeth probably originate from the host tissue.