Enamelin compartmentalization in developing porcine enamel.

The tissue compartmentalization of enamelin-processing products has been investigated in developing pig enamel using a sequential extraction procedure. Only trace amounts of enamelin-processing products were detected in simulated enamel fluid extracts, suggesting that enamelins are not solubilized in the matrix to any great extent. Subsequent phosphate buffer extraction desorbed and extracted several enamelin-processing products that were presumably bound to the mineral phase. A 35-kD processing product dominated the phosphate extract, suggesting that enamelin processing leads to an accumulation of this mineral-bound molecule. Dissociative extraction with urea subsequently extracted the remainder of the enamelin-processing products present. This material was presumably present in the tissue in an aggregated insoluble state. Several enamelin-processing products were only extracted by specific extraction procedures, suggesting that different enamelin-processing products are differentially compartmentalized. This may indicate that specific enamelin-processing products have different functions. In contrast to amelogenins, which are processed in the deeper tissue to generate products having a low affinity for the mineral, enamelin processing appears to produce products (those enamelins desorbed by phosphate buffer) that have a high affinity for the mineral. These products, appearing in the deeper enamel layers, may serve to influence crystal growth kinetics in the absence of any mineral-binding amelogenins.